微波-水热法制备钛酸钡纳米晶

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单分散纳米钛酸钡晶体的微波水热合成与表征_推荐一个研究型综合实验

水热条件下ＢａＴｉＯ３晶粒形成机理仍是一个有争议的课题，但大多数研究认为，遵从的是溶解－沉淀的机理。［３］如图２所示，钛源水解形成无定形
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＊通信联系人，Ｅ－ｍａｉｌ：ｃｈｅｎｐｅｉ＠ｓｎｎｕ．ｅｄｕ．ｃｎ
关键词研究型综合实验微波合成单分散纳米钛酸钡晶体表征ＤＯＩ：１０．１３８８４／ｊ．１００３－３８０７ｈｘｊｙ．２０１３１００１２８
为适应社会对高水平人才的需求，我国高等院校以培养厚基础、宽口径、高素质、强能力的复合型人才为目标，深化教学改革，其中，增设研究型综合实验成为教学改革的一个亮点。不同于以往的验证型实验，研究型综合实验不但锻炼了学生动手能力，而且激发了学生的求知欲、拓宽了其知识面，对培养学生创新思维能力具有重要意义。
５产物表征
采用Ｘ射线粉末衍射仪（ＸＲＤ）和激光拉曼光谱仪对产物的晶体结构进行表征；利用红外光谱仪（ＩＲ）、热失重分析（ＴＧ）和接触角测试研究油酸分子在钛酸钡表面的包覆作用；利用透射电子显微镜（ＴＥＭ）和高分辨ＴＥＭ观察产物的晶体形貌和晶格。５．１晶体结构表征
室温下，立方相钛酸钡是拉曼惰性的，而四方相钛酸钡是拉曼活性的，故拉曼光谱可灵敏地检测四方相的存在。从图３（ｂ）可以看出，在１８３、２６１、３０５、５２０、７１５ｃｍ－１出现了拉曼峰，其中３０５ｃｍ－１和７１５ｃｍ－１是四方相钛酸钡的典型拉曼特征峰。［４］这说明所合成的钛酸钡主相为立方相，同时存在少量四方相。

纳米钛酸钡的研究进展

。＋ｍｕｌｔｉｌａｙｅｒ”’“”ｃ，３，ｐ４ｃｉｔｏｒｓ（ＭＬ。‘焉Ｊ·ｍ。…”７ …叭“““·……。…“·Ｗｉｔｈ讣。ｄｃｖ。¨Ｐ…““ｏｆ”””一
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了解纳米钛酸钡。本文介绍ｒ纳钛酸钡的瓷电容器，电光显示板，记忆材料，聚合物
主要性质和应用领域对纳米钛酸钡制备方基复合材料以及涂层等阻ｎＩ。而纳米钛酸
钡作为催化材料是它的另一个重要应用。刘海波等人Ｉｌ”研究了用凝胶一溶胶法制备得到粒径约为５２．４ｎｍ的ＢａＴｉＯ，对甲基橙的光催化降解率可达８１．７％。王春风等人１１４１考察了稀十掺杂的纳米钛酸钡在二氧化碳重整甲烷制合成气反应中的催化活性，结果表明掺杂稀士Ｌａ，Ｃｅ，Ｙｂ，Ｓｍ的镍基钛酸钡催化剂在二氧化碳重整甲烷反应中活性高于未掺杂稀土的镍基钛酸钡催化剂的活性，当稀土掺杂量为０．２％时，催化剂具有最高的反应活性。
高可靠惟、多功能手ｒｌ／ｂ犁化方向的高速发人，纳米钛酸钡已，“泛地应用于制造陶瓷
媵，对制备满足性能要求的钛酸钡材料提敏感元件，尤其是正温度系数热敏电阻
出了更高的要求…。纳米钛酸钡的制备和（Ｆｒｃ），多层陶瓷电容器（ＭＬＣＣＳ），热电元
研究Ｌ！成为研究的一个热点。为了更好的件，压电陶瓷，声纳，红外辐射探测，晶体陶
ａ｝ｏｒｏｆｃｓｅａｒｃｈｄｅｖｅｌｏｐｍｅｎｔＴｈｉｓｐａｐｅｒｄｅｓｃｒｉｂｅｄ！机械能的转换。温度在ＴＣ（１２０＂Ｃ）附近时，
ｔｈｅ１１ａｕｉｒｅａｎｄａｐｐｌｉｃａｔｉｏｎ。ｆｎａｎｐｂａｒｉｕｍｔｉｔａｎａｔｅ｝ＢａＴｉＯ，的介电常数高达６０００以上，远人

微波照射制备钛酸钡纳米晶

聚轻．具有比传统的水热法更突出的优点『５】。利用微波水热合成不仅可极大地加速合成与晶化的速度。而且可极大地改善目标产物的品质。使
中使用最广泛的材料之一。四方相ＢＴＯ可用于如ａｉ
制备多层电容器（Ｃ）４、温度系数（Ｔ）敏ＭＬＣ［］正１ＰＣ热电阻、电陶瓷等的材料。压ＢＴＯ陶瓷粉体传统的制备方法是以ＢＣａｉａＯ
ＡｂｔａｔＣｂｃａｉｍｔａａａｏｒｓｌｗｒｒｐｒｄｂｉＣＨ）ａｄＣＨ５ＨｍｘｕｅｉａＩａｕｏｓｓｒｃ：ｕｉｂｒｔｔｎｎｃｙｔｓｅｅｅａｅｙＴ（４ｇ２ＯｉｔｒｔＢＣ２ｑｅｕｕｉｎｅａｐＯ４ｎｗｈ
ＳｎＹｕＷＵｎ — ｕＨＵＡｎＨＩＸｉ — ＤｏｇＨｉＰｉｇ
（ｃｏｌｆＣｅｉｒｎｈｍｉｌｎｉｅｒｇＮａｔｇＵｉｒｉ，ａｔｇＪｎｓ２０７ＳｈｏｈｍｓｙａｄＣｅｃｇｎｅｉ，ｎｎｎｅｓｙＮｎｏ，ｉｇｕ２６０）ｏｔａＥｎｏｖｔｎａ
Ｋｅｒｓａｉｍｔｎｔ；ｃｏｖｒａｉｔｎｎｎｃｙｔｌｙｒｔｅｍａｙｗｏｄ：ｂｒｕｔａａｅｍｉｒｗａｅｉｄａｉ；ａｏｒｓａ；ｈｄｏｈｒｌｉｒｏ
钛酸钡（ａｉ３典型的铁电材料．电子陶瓷ＢＴＯ）是是

微波—水热法合成纳米钛酸钡原料

微波—水热法合成纳米钛酸钡原料陈舰;杨浩南【摘要】结合水热法和微波加热的优点,设计了三因素三水平的正交试验方案,采用微波—水热法合成纳米钛酸钡(BaTiO3)原料.用X射线衍射仪(XRD)、激光粒度分析仪、扫描电子显微镜(SEM)对合成的BaTiO3原料进行检测和表征,用直观分析法处理结果,得出BaTiO3纳米原料的最佳合成工艺:反应温度70℃,反应时间30 min,反应物浓度0.2 mol/L.【期刊名称】《五邑大学学报（自然科学版）》【年(卷),期】2013(027)001【总页数】6页(P69-74)【关键词】微波—水热法;纳米BaTiO3原料;激光粒度分析【作者】陈舰;杨浩南【作者单位】东莞理工学院化学与环境工程学院,广东东莞 523808;东莞理工学院化学与环境工程学院,广东东莞 523808【正文语种】中文【中图分类】O611.4钛酸钡（BaTiO3），又称偏钛酸钡，是一种具有良好铁电性和很强介电性的精细化工产品. BaTiO3原料作为电子工业和特种陶瓷等高新技术的重要基础原料，主要应用于多层陶瓷电容器（MLCC）、电子计算机的记忆元件、晶界陶瓷电容器、正温度系数热敏陶瓷（PSTR）、半导体陶瓷等. 电子产品的快速增长，使得对具有更小粒径、更高纯度、形貌均匀的BaTiO3原料的需求量越来越大.目前BaTiO3原料的合成方法主要有固相烧结法、化学沉淀法、溶胶凝胶法、微乳液法、水热合成法等. 与传统合成法相比，微波—水热法在很多方面表现出了优势，如瞬间使物体整体温度达到结晶化温度，沉淀凝胶快速溶解均匀成核并迅速达到饱和，结晶化时间缩短[1]. 微波—水热法合成BaTiO3的影响因素有：溶液pH值[2]、反应时间[3]、钡钛比例[4]、反应温度[5]、分散剂[5]等，但最佳工艺参数还在探索中. 本文选用钛酸丁酯和硝酸钡Ba(NO3)2为原料，NaOH为矿化剂，设计三因素三水平的正交试验方案，寻找用微波—水热法制备BaTiO3原料的最佳工艺条件.：化学纯，天津市光复精细化工研究所；Ba(NO3)2：分析纯，天津市福晨化学试剂厂；NaOH：分析纯，汕头市西陇化工厂有限公司；无水乙醇：分析纯，天津市大茂化学试剂厂；冰醋酸：分析纯，天津市大茂化学试剂厂.微波固相合成仪：T640，莱伯泰科有限公司；恒温磁力搅拌器：81-2，上海司乐仪器厂；电子天平：FA2004，上海舜宇恒平科学仪器有限公司；电热鼓风恒温干燥箱：101-1A，上海讯能电热设备有限公司；X射线衍射仪：UItima IV，日本理学株式会社；激光粒度分析仪：RISE-2008，济南润之科技有限公司；扫描电子显微镜：JSM-7600F，日本电子株式会社.1.2 实验操作1）将Ba(NO3)2溶于蒸馏水，配制成0.3 mol/L的Ba(NO3)2溶液；将溶于无水乙醇，配制成0.3 mol/L的溶液；将NaOH溶于蒸馏水，配制成2 mol/L的溶液.2）取100 mLNaOH溶液加热至80℃，冷却至室温，在恒温磁力搅拌下，逐滴加入100 mL 溶液，最后加入100 mL Ba(NO3)2溶液. 混合均匀后，用pH试纸检测pH值（＞13）. 将乳白液倒入反应釜中，设置好反应时间和反应温度，在微波固相合成仪中反应.3）反应结束后，将反应液抽滤，再依次用稀醋酸酸洗、水洗、醇洗. 所得固体用烘箱在85℃下烘6 h，得到白色原料.4）分别控制反应物Ba(NO3)2和浓度为0.2 mol/L、0.3 mol/L、0.4 mol/L，反应温度为70℃、85℃、90℃，反应时间为10 min、30 min、40 min，重复上述三步骤，制备9种条件下的9个产物并编号.5）X射线衍射仪实验条件：Cu靶，工作电压40 kV，工作电流40 mA.2 结果与分析控制钡钛物质的量之比为1:1，溶液pH≥13，干燥时间和干燥温度（85℃）一定，做9组实验，用X射线衍射仪对合成原料进行晶相检测，用激光粒度分析仪测量粉体颗粒的粒度，用扫描电子显微镜扫描合成BaTiO3原料的表面形貌，用直观分析法对样品进行分析，找出最佳工艺参数.2.1 实验正交方案综合郭立童[3]、赵艳敏[5]等人的文献，本文选择反应温度、反应时间、反应物浓度作为正交试验方案的三个因素，具体见表1.表1 试验因素水平因素反应温度/℃反应时间/min反应物浓度/（） 170100.2 285300.3 390400.42.2 9个产物样品的晶面间距XRD是鉴定物质晶像、研究晶体结构快速有效的方法. 从9个样品的XRD谱图可以看出：1）9个样品的XRD图谱与标准卡片PDF Card NO:00-031-0174立方相BaTiO3相比，其衍射角及相对应的衍射强度基本一致，由此可以确定合成的原料主晶相为立方相BaTiO3. 2）9个样品的谱图基准线都比较粗糙，除2号样外，其他谱图还出现了明显的杂峰，这表明2号样品的结晶纯度最高、杂质含量最少. BaTiO3原料烧结后活性更高，其介电性能和压电性能也大大提高. 晶面间距是衡量BaTiO3原料是否合格的重要指标，晶面间距小符合BaTiO3原料高纯细的追求. 晶面间距越小，说明BaTiO3晶体分布越窄. 通过XRD谱图生成的报告可以得到9个合成样品晶体（110）面的晶面间距，见表2.表2 样品的晶面间距样品编号反应条件晶面间距/ang 反应温度/℃反应时间/min 反应物浓度/（） 11（70）1（10）2（0.3）3.69 21（70）2（30）1（0.2）2.85 31（70）3（40）3（0.4）2.33 42（85）1（10）3（0.4）3.71 52（85）2（30）2（0.3）3.69 62（85）3（40）1（0.2）3.69 73（90）1（10）1（0.2）2.87 83（90）2（30）3（0.4）2.34 93（90）3（40）2（0.3）2.85从表3反应条件的极差R值可以看出，对晶面间距而言，反应温度的极差最大，其次是反应物浓度，最次是反应时间. 所以，微波—水热法合成BaTiO3原料的最佳工艺条件：反应温度70 ℃，反应时间30 min，反应物浓度0.2 mol/L.表3 极差分析极差晶面间距反应温度反应时间反应物浓度 K108.8710.2709.41K211.0909.3910.23 K308.0608.8708.38 R102.9603.4203.14R204.0003.1303.41 R302.6902.9602.79 极差01.3100.4600.622.3 最佳工艺产品的检验2.3.1 粒度本文采用激光粒度分析仪测量微波—水热法在最佳工艺条件下合成原料的粉体颗粒粒度（图1），并与市售标准品的粉体颗粒粒度（图2）对比.图1 最佳工艺合成粉体的粒度分布图图2 市售标准品粒度分布图从图1和图2可以看出：1）微波—水热法最佳工艺条件下合成的BaTiO3粉体平均颗粒粒度为0.967 μm，比市售标准品的平均颗粒粒度（2.337 μm）小2.4倍左右. 2）微波—水热法最佳工艺条件下合成的BaTiO3粉体的粒径分布比市售标准品的分布宽，说明合成的样品拥有更细的粒径，但是粒径大小分布的均匀性还有待提高.2.3.2 表面形貌和晶体尺寸SEM常用来观察样品表面形貌（断口等），本文采用SEM来测试最佳工艺条件下合成粉体的表面形貌和晶体尺寸，并与其他条件下的2个样品作对比，具体见图3、4、5.图3的晶体为梭子形，原料的平均粒径在0.74 μm左右，形貌模糊，图形不规则，结晶纯度低. 图4的晶体中出现大圆球，有明显的团聚现象，表明原料质量较差.图5的晶体形状为球形，颗粒分布均匀，没有团聚现象，晶体直径平均在50 nm，其表面形貌和晶体尺寸比较理想.图3 反应温度70℃，反应时间10 min，反应物浓度0.3 mol/L的SEM图图4 反应温度70℃，反应时间40 min，反应物浓度0.4 mol/L的SEM图图5 最佳工艺粉体的SEM图2.4 讨论相比传统工艺，微波—水热法显示出了明显的优势，具体见表4.表4 不同工艺的粒径比较工艺反应温度/℃反应时间/min粒径/nm 本文的微波—水热法07003050左右罗昆鹏[2]的微波水热法07001060～100 赵艳敏[6]等人的传统水热法24048060～100 全学军[7]等人的草酸络合物沉淀法800060540 续京[8]等人的化学沉淀法080060803 结论本实验采用微波—水热法合成纳米BaTiO3原料的最佳工艺参数为：反应温度70 ℃，反应时间30 min，反应物浓度0.2 mol/L. 相比于传统工艺，微波—水热法更具优势，如加热速度快、反应温度低、反应时间短、反应条件更容易达到，合成产物的粒径更细、分散性好、表面形貌更均匀.参考文献[责任编辑：熊玉涛]Nano-BaTiO3 Raw Materials Synthesized by Microwave-hydrothermal MethodCHEN Jian, YANG Hao-nan(College of Chemistry and Environmental Engineering, Dongguan University of Technology,Dongguan 523808, China)Abstract: With the advantages of the hydrothermal method and microwave heating method, Barium Titanium Oxide (BaTiO3) raw materials are synthesized by using microwave-hydrothermal method. Threefactors with three levelsare considered in the experiment, thesyntheticpowders are tested and characterized via usingX-raydiffraction(XRD), laser particle size analysis instrument and scanning electronmicroscopy (SEM). Intuitiveanalysis is adopted to detect the experiment results, theoptimal parameters for Barium Titanium Oxide (BaTiO3) raw materials synthesizing is concluded：reaction temperature is 70 ℃，reaction time is 30 min, reactant concentration is 0.2 mol/L.Key words: microwave-hydrothermal method; nano-BaTiO3 raw materials; laser particle size analysis文章编号：1006-7302（2013）01-0069-06中图分类号：O611.4文献标志码：A收稿日期：2012-11-05作者简介：陈舰（1955—），男，四川自贡人，副教授，主要从事无机非金属材料的研究.微波固相合成仪：T640，莱伯泰科有限公司；恒温磁力搅拌器：81-2，上海司乐仪器厂；电子天平：FA2004，上海舜宇恒平科学仪器有限公司；电热鼓风恒温干燥箱：101-1A，上海讯能电热设备有限公司；X射线衍射仪：UItima IV，日本理学株式会社；激光粒度分析仪：RISE-2008，济南润之科技有限公司；扫描电子显微镜：JSM-7600F，日本电子株式会社.1）将Ba(NO3)2溶于蒸馏水，配制成0.3 mol/L的Ba(NO3)2溶液；将溶于无水乙醇，配制成0.3 mol/L的溶液；将NaOH溶于蒸馏水，配制成2 mol/L的溶液.2）取100 mLNaOH溶液加热至80℃，冷却至室温，在恒温磁力搅拌下，逐滴加入100 mL 溶液，最后加入100 mL Ba(NO3)2溶液. 混合均匀后，用pH试纸检测pH值（＞13）. 将乳白液倒入反应釜中，设置好反应时间和反应温度，在微波固相合成仪中反应.3）反应结束后，将反应液抽滤，再依次用稀醋酸酸洗、水洗、醇洗. 所得固体用烘箱在85℃下烘6 h，得到白色原料.4）分别控制反应物Ba(NO3)2和浓度为0.2 mol/L、0.3 mol/L、0.4 mol/L，反应温度为70℃、85℃、90℃，反应时间为10 min、30 min、40 min，重复上述三步骤，制备9种条件下的9个产物并编号.5）X射线衍射仪实验条件：Cu靶，工作电压40 kV，工作电流40 mA.控制钡钛物质的量之比为1:1，溶液pH≥13，干燥时间和干燥温度（85℃）一定，做9组实验，用X射线衍射仪对合成原料进行晶相检测，用激光粒度分析仪测量粉体颗粒的粒度，用扫描电子显微镜扫描合成BaTiO3原料的表面形貌，用直观分析法对样品进行分析，找出最佳工艺参数.综合郭立童[3]、赵艳敏[5]等人的文献，本文选择反应温度、反应时间、反应物浓度作为正交试验方案的三个因素，具体见表1.XRD是鉴定物质晶像、研究晶体结构快速有效的方法. 从9个样品的XRD谱图可以看出：1）9个样品的XRD图谱与标准卡片PDF Card NO:00-031-0174立方相BaTiO3相比，其衍射角及相对应的衍射强度基本一致，由此可以确定合成的原料主晶相为立方相BaTiO3. 2）9个样品的谱图基准线都比较粗糙，除2号样外，其他谱图还出现了明显的杂峰，这表明2号样品的结晶纯度最高、杂质含量最少. BaTiO3原料烧结后活性更高，其介电性能和压电性能也大大提高. 晶面间距是衡量BaTiO3原料是否合格的重要指标，晶面间距小符合BaTiO3原料高纯细的追求. 晶面间距越小，说明BaTiO3晶体分布越窄. 通过XRD谱图生成的报告可以得到9个合成样品晶体（110）面的晶面间距，见表2.从表3反应条件的极差R值可以看出，对晶面间距而言，反应温度的极差最大，其次是反应物浓度，最次是反应时间. 所以，微波—水热法合成BaTiO3原料的最佳工艺条件：反应温度70 ℃，反应时间30 min，反应物浓度0.2 mol/L.2.3.1 粒度本文采用激光粒度分析仪测量微波—水热法在最佳工艺条件下合成原料的粉体颗粒粒度（图1），并与市售标准品的粉体颗粒粒度（图2）对比.从图1和图2可以看出：1）微波—水热法最佳工艺条件下合成的BaTiO3粉体平均颗粒粒度为0.967 μm，比市售标准品的平均颗粒粒度（2.337 μm）小2.4倍左右. 2）微波—水热法最佳工艺条件下合成的BaTiO3粉体的粒径分布比市售标准品的分布宽，说明合成的样品拥有更细的粒径，但是粒径大小分布的均匀性还有待提高.2.3.2 表面形貌和晶体尺寸SEM常用来观察样品表面形貌（断口等），本文采用SEM来测试最佳工艺条件下合成粉体的表面形貌和晶体尺寸，并与其他条件下的2个样品作对比，具体见图3、4、5.图3的晶体为梭子形，原料的平均粒径在0.74 μm左右，形貌模糊，图形不规则，结晶纯度低. 图4的晶体中出现大圆球，有明显的团聚现象，表明原料质量较差.图5的晶体形状为球形，颗粒分布均匀，没有团聚现象，晶体直径平均在50 nm，其表面形貌和晶体尺寸比较理想.相比传统工艺，微波—水热法显示出了明显的优势，具体见表4.本实验采用微波—水热法合成纳米BaTiO3原料的最佳工艺参数为：反应温度70 ℃，反应时间30 min，反应物浓度0.2 mol/L. 相比于传统工艺，微波—水热法更具优势，如加热速度快、反应温度低、反应时间短、反应条件更容易达到，合成产物的粒径更细、分散性好、表面形貌更均匀.【相关文献】[1] 马麦霞，张光霞. 微波水热合成Mn掺杂BaTiO3纳米原料[J]. 硅酸盐通报，2010, 29(1): 108.[2] 罗昆鹏，微波水热合成钛酸钡纳米原料[D]. 西安：西安科技大学，2009: 17-44.[3] 郭立童，罗宏杰，郭立芝. 钛酸钡粉体的微波水热合成[J]. 中国陶瓷，2005, 41(1): 13.[4] 吴东辉，施新宇，张海军. 草酸盐共沉淀法制备钛酸钡粉体研究[J]. 压电与声光，2009, 31(2): 252.[5] 赵艳敏，冯绣丽，王公应. 超细钛酸钡粉体的水热合成[J]. 合成化学，2005, 13(3): 301-303.[6] 赵艳敏，王越，王公应. 纳米钛酸钡的水热合成进展[J]. 合成化学，2003(4): 300-306.[7] 全学军，李大成. 草酸络合物沉淀法制备超细钛酸钡粉的研究[J]. 四川大学学报，2001, 33(4):80-81.[8] 续京，张炎. 化学沉淀法制备纳米钛酸钡粉体[J]. 广西大学学报：自然科学版，2011(3): 445-449.。

水热法制备BaTO3纳米粉体

汤黎辉,张群飞,马金明,肖长江,栗正新(河南工业大学材料科学与工程学院,郑州450001)BaTiO 3纳米粉体的合成方式及合成粉末的样本表征,采取水热法合成方法,合成得到钛酸钡。

通过X 射线衍射、扫描电子显微镜表征手段以及JADE 、Origin 等软件的分析,得出其物相、晶体结构、颗粒大小以及外观形貌。

经过实验,使用水热法合成方式,能够制备出高品质的钛酸钡纳米粉末。

结果表明:用水热法得到了纯的钛酸钡粉体,粉体的晶粒大小较均匀,晶粒尺寸约为39.51nm,粉体的晶体结构为四方结构,形貌为类球形。

;纳米粉体;水热法;晶体结构;晶粒尺寸由于具有出色的介电性能，钛酸钡（BaTiO 3）已经成功地发展出了各种电子器件，如多层陶瓷电容器、正温度系数热敏电阻、动态随机存储器、声呐传感器、压电换能器以及各种光电子元件，从而在电子领域发挥着重要的作用，并且已经成为电子陶瓷领域的主要原材料[1,2]。

目前制备钛酸钡粉体最常用的方法主要有固相法、共沉淀法、微乳液合成方法、水解溶胶-凝胶法等。

固相法作为一种传统的合成工艺，具有制备产率高，操作简单等优点，但是，这种合成方法在制备过程中存在合成温度高、合成的粉体颗粒粗大、较高的杂质含量以及组分均匀度不高等缺点，一般作为低端产品合成时的首选工艺。

共沉淀法制备钛酸钡粉体难以形成均匀的沉淀物，而且颗粒容易团聚，粒径分布宽，产品质量不稳定[3]。

微乳液合成方法制备产物需要大量助剂、改性剂和有机剂，导致成本较高，而且还易引入杂质且产能有限，所以该合成方法目前还没有被广泛的使用，仅仅处于实验室研究中[4]。

凝胶法虽然可行，但由于技术复杂、时间较久，使得它的水解效果不易掌握。

相比之下，水热法更加经济实惠，可以在较短的时间内完成钛酸钡的生产，同时也能够保证产品的质量，能够满足更严格的质量标准[5]。

水热法合成粉体，能够在低温水溶液中得到分散性好的BaTiO 3超细粉体，合成的粉体晶粒发育比较完整，并且在水热法实验过程中，不需要经历高温的煅烧以及后期的球磨过程，进而可以避免了杂质的引入和球磨对粉体结构的破坏，从而有效地消除了杂质及其他形态问题，故文章实验采用水热法制备BaTiO 3纳米粉体，并对其进行深入研究。

水热法合成钛酸钡

Hydrothermal Synthesis of Barium Titanate:Effect of Titania Precursor and Calcination Temperature on Phase TransitionNatarajan Sasirekha,Baskaran Rajesh,and Yu-Wen Chen*Department of Chemical Engineering,Nanocatalysis Research Center,National Central Uni V ersity,Chung-Li320,Taiwan,Republic of ChinaNanosized barium titanate powders were synthesized by a hydrothermal method.The effect of titania precursorson the phase transition of BaTiO3with respect to Ba/Ti ratio,reaction temperature,reaction time,and calcinationtemperature was investigated.The synthesized materials were characterized by X-ray diffraction,scanningelectron microscopy,and transmission electron microscopy.BaTiO3in pure cubic phase with sphericalmorphology was observed with a lower calcination temperature,Ba/Ti ratio,reaction temperature,and time.Increase in the tetragonal phase was ascertained in treatments at higher reaction temperature with a longerreaction time.The lattice hydroxyl release is believed to be the reason for tetragonality at high reaction andcalcination temperatures.To prepare tetragonal BaTiO3using HClO4-TiO2,the optimum synthesis conditionsviz.,Ba/Ti ratio,reaction temperature,and reaction time,are1.2,160°C,and3h,respectively,at a calcinationtemperature of1150°C.The reaction time and reaction temperature for the cubic-tetragonal phasetransformation of BaTiO3shifted toward shorter reaction time and lower reaction temperature when TiO2was synthesized by hydrolysis using HClO4as the acid catalyst.1.IntroductionBarium titanate(BaTiO3),one of the most well-known ferroelectrics,has played an important part in the modern ceramic industry since the discovery of ferroelectric properties in the tetragonal phase of BaTiO3during the1940s.1It has been broadly used as a dielectric material in multilayer ceramic capacitors(MLCCs),2-4printed circuit boards(PCBs),5,6dy-namic random access memory(DRAM),positive temperature coefficient of resistance thermistors(PTCRs),piezoelectric sensors for ultrasonic and measuring devices,pressure transduc-ers,infrared detectors,and electrooptic devices7-9due to its unique perovskite structure(ABO3)and exceptionally high dielectric[(2-5)×103]10and piezoelectric properties at room temperature.However,these outstanding behaviors mainly depend on the crystal structure,shape,size,stoichiometry, homogeneity,and surface properties of BaTiO3,which in turn depends on the synthesis method.Among the crystal structures of BaTiO3,the cubic phase exhibits paraelectric properties,while the tetragonal phase shows ferroelectric properties.The direct generation of tetragonal BaTiO3is of considerable interest. The conventional synthesis of barium titanate compounds typically involves high-temperature(∼1200°C)calcinations of a BaCO3and TiO2powder mixture,which often results in low purity and polydispersity due to high reaction temperature and heterogeneous solid-phase reaction.11,12Nevertheless,fine Ba-TiO3ceramics can be prepared by wet-chemistry synthesis techniques,including the coprecipitation method,13coprecipi-tation in combination with the inverse microemulsion method,14,15 sol-gel processing,16,17the hydrothermal method,18-21spray pyrolysis,22the oxalate route,23the high-temperature ceramic route,the microwave hydrothermal method,24-27and the polymeric precursor method.28Hydrothermal synthesis for the preparation of crystalline BaTiO3has gained popularity recently.29-33It involves the chemical reactions of Ba(OH)2,TiO2,or gels of Ba-Ti acetate mixtures at a high temperature.It has the advantage of producing finer particles with more uniform size.In addition,the interac-tion between the solid and fluid phases determines the physical characteristics of BaTiO3,and hence,the synthesis allows one to control the particle size by adjusting the synthesis parameters, such as the reaction temperature,time,and pH values.The synergistic effect of solvent,temperature,and pressure on the ionic reaction equilibrium in the hydrothermal reaction medium can stabilize the formation of BaTiO3and retards the formation of impurities.Also,the precursors for the preparation of BaTiO3 by hydrothermal synthesis are readily available,inexpensive, and easy to handle,which makes the hydrothermal synthesis an easy and effective method to adopt for the synthesis of BaTiO3.Although the hydrothermal synthesis has the above-mentioned advantages,the formation and growth mechanisms in BaTiO3synthesis have not been well understood.There are a few articles about the study of phase transformation of BaTiO3 with preparation conditions.However,so far there is no report about the effect of titania precursor,which plays a vital role in the growth mechanism of BaTiO3synthesis,on the phase transformation of BaTiO3.In this paper,a systematic investiga-tion on the effect of titania precursor on phase transformation of BaTiO3with respect to Ba/Ti ratio,reaction temperature, reaction time,and calcination temperature is presented.2.Experimental Section2.1.Hydrothermal Synthesis of BaTiO3.Barium titanate powders were synthesized by hydrothermal method.All the reagents used were of analytical grade.Hydrothermally produced TiO2particles34prepared using hydrochloric acid and perchloric acid as acid precursors were used as the titania source.The detailed characteristics of these materials have been presented in our previous paper.34Ba(OH)2‚8H2O(Showa Chemical Co., Ltd.)and TiO2powder(rutile)34were mixed with a Ba/Ti ratio (1.2,1.4,1.6,1.8,2.0)in a50mL autoclave with45mL of deionized water.The autoclave was sealed,shaken,and placed in an oven at160°C for a variable reaction period ranging from*To whom correspondence should be addressed.Tel.:(886)3422751,ext34203.Fax:(886)34252296.E-mail:ywchen@cc.ncu.edu.tw.1868Ind.Eng.Chem.Res.2008,47,1868-187510.1021/ie070986m CCC:$40.75©2008American Chemical SocietyPublished on Web02/16/20083to 24h.After cooling naturally to room temperature,the contents of the autoclave were diluted in 90mL of 0.1M formic acid with stirring for 5min in an attempt to remove any BaCO 3formed and the addition of excess Ba 2+to the starting solution.The mixture was filtered and washed with distilled water (500mL)three times,and the residue was dried in oven at 100°C for 24h.2.2.Characterization.The crystalline phase of BaTiO 3was analyzed by powder X-ray diffraction (XRD)using a Siemens D500automatic powder diffractometer.Nickel-filtered Cu K R radiation (λ)0.15418nm)was used with a generator voltage of 40kV and a current of 29mA.Bragg -Brentano focusing geometry was employed with an automatic divergence slit (irradiated sample length was 12.5nm),a receiving slit of 0.1nm,a fixed slit of 4°,and a proportional counter as a detector.It was operated in the step scan mode,at scanning speeds of 0.1°2θ/s and 1s step time in the range 20-80°for barium titanate.Scherrer’s equation 35was used to calculate the crys-tallite size of barium titanate crystals from the full width at half-maximum of the XRD peak.The morphology of the particles was analyzed by scanning electron microscopy (SEM)and transmission electron micros-copy (TEM).SEM images were acquired with a Hitachi S-800field emission microscope using an acceleration voltage of 20kV.The samples were coated with Au prior to analysis and imaged directly.TEM images were obtained on a JEOL JEM-2000FX Πmicroscope using an electron beam generated by a tungsten filament and an accelerating voltage of 160kV,a beam diameter of approximately 1-2µm,and an objective lens aperture of 20µm.The sample grids were prepared via sonication of powdered sample in ethanol for 10min and evaporating 1drop of the suspension onto a carbon-coated,porous film supported on a 3mm,200-300mesh copper grid.TEM images were recorded at a magnification of 100000-400000×.The magnification was calibrated in pixels per nanometer on the camera.3.Results and Discussion3.1.Effect of Ba/Ti Ratio.BaTiO 3powder,prepared with Ba/Ti ratio in the range of 1.2-2.0,was characterized by XRD,SEM,and TEM techniques to study the cubic -tetragonal phase transformations and surface modifications of BaTiO 3.The ratio of Ba/Ti was chosen to be greater than 1to avoid contamination of BaTiO 3(s)with excess TiO 2(s)under the conditions of hydrothermal synthesis.24Furthermore,Ba/Ti >1increases the pH of the solution,which is an important thermodynamicvariable for the synthesis of perovskite materials,and helps to avoid the addition of an alkaline mineralizer to facilitate the formation of BaTiO 3.According to the thermodynamic calcula-tions of stability diagrams for the hydrothermal Ba -Ti system,high pH and Ba/Ti >1are necessary for the synthesis of high-purity BaTiO 3crystals.28XRD patterns of the as-synthesized BaTiO 3,with Ba/Ti ratios of 1.2,1.4,1.6,1.8,and 2.0,showed the characteristic peaks of both cubic BaTiO 3(JCPDS File No.79-2263)and those of BaCO 3for both TiO 2precursors.Modest BaCO 3contamination was noted in almost all the samples due to the introduction of airborne CO 2,which would dissolve as CO 32-and reacts with Ba 2+to form BaCO 3during the posttreatment.26,36The formation of BaCO 3,observed in this work,is quite common in the hydrothermal processing as BaCO 3can precipitate at lower pH values than those needed to precipitate BaTiO 3.24AccordingtoFigure 1.XRD patterns of BaTiO 3synthesized at various Ba/Ti ratios using (a)HCl-TiO 2and (b)HClO 4-TiO 2precursors and washed with formic acid followed by calcination at 900°C (2h).Table 1.Effect of Ba/Ti Ratio and Calcination Temperature on the Crystalline Phase of BaTiO 3calcination temp (°C)Ti precursor Ba/Ti ratio synthesis temp (°C)synthesis time (h)9001150crystalline phase HCl-TiO 21.21606--cubic 1.41606--cubic 1.61606--cubic 1.81606--cubic2.01606--cubic HClO 4-TiO 21.21606--cubic 1.41606--cubic 1.61606--cubic 1.81606--cubic2.01606--cubic HCl-TiO 21.21606yes -cubic 1.41606yes -cubic 1.61606yes -cubic 1.81606yes -cubic2.01606yes -cubic HClO 4-TiO 21.21606yes -cubic 1.41606yes -cubic 1.61606yes -cubic 1.81606yes -cubic2.01606yes -cubic HCl-TiO 21.21606-yes cubic 1.41606-yes cubic 1.61606-yes cubic 1.81606-yes cubic2.01606-yes cubic HClO 4-TiO 21.21606-yes tetragonal 1.41606-yes tetragonal 1.61606-yes tetragonal 1.81606-yes tetragonal2.01606-yestetragonalInd.Eng.Chem.Res.,Vol.47,No.6,20081869the thermodynamic stability diagram of Ba -Ti systems,BaCO 3precipitates at lower pH values than those needed to precipitate BaTiO 3.28Moreover,the formation of BaCO 3is more predomi-nant in BaTiO 3prepared using HClO 4-TiO 2,which indicates its lower pH compared with those prepared using HCl-TiO 2.The relative pH of HClO 4is lower than that of HCl as the p K a values of HClO 4and HCl are -10and -7,respectively.37The XRD results of the as-synthesized BaTiO 3illustrate the absence of apparent peak splitting at 2θ)45°,which corre-sponds to the tetragonal phase of BaTiO 3(JCPDS Card No.5-0626)and hence confirmed the cubic structure with symmetry Pm 3m .In order to remove BaCO 3,the powders were washed with formic acid and calcined at 900°C for 2h.Figure 1shows XRD patterns of BaTiO 3chemically treated with formic acid and calcined at 900°C,which confirms the removal of BaCO 3from BaTiO 3prepared using HCl-TiO 2and HClO 4-TiO 2.Moreover,it indicates that there is no change in the cubic phase of BaTiO 3upon treatment with formic acid.The effect of Ba/Ti ratio and calcination temperature on the crystal structure of BaTiO 3is summarized in Table 1.It can be observed that,even at a Ba/Ti molar ratio of 2without heat treatment,the tetragonal splitting of the diffraction peaks corresponding to the (200)and (002)planes of the perovskite BaTiO 3could not be distinguished,indicating the presence of pure cubic crystalline phase.Shi et al.36observed tetragonal BaTiO 3crystallites when the precursor with high Ba/Ti molar ratio of 3was used,which reduces the probability of forming barium vacancies and stabilized tetragonal phase.The influence of calcination temperature at various Ba/Ti ratios on the cubic -tetragonal phase transition of BaTiO 3can be observed by comparing Figures 1and 2.Figure 2shows the XRD patterns of BaTiO 3prepared using HCl-TiO 2and HClO 4-TiO 2,subjected to calcination at 1150°C.For BaTiO 3samples prepared using HCl-TiO 2,the XRD results show that the crystalline phase is metastable cubic phase for all the samples at 900and 1150°C.The peaks are very sharp,indicating that the crystalline structure is well developed.Generally,the tetragonality of BaTiO 3is deduced from the plane spacing of (002)over that of (200);the corresponding peak appears near 45°in the XRD patterns.Because the peak splitting at 45°is a predominant one to confirm the formation of tetragonal phase,tetragonal splitting of the peaks corresponding to (200)and (002)planes have been chosen to verify the formation of tetragonal phase.Normally,BaTiO 3cubic -tetragonal phase changes begin at 900and 1150°C,but for BaTiO 3prepared using HCl-TiO 2the phase transformation does not proceed to completion even at 1150°C.In the case of BaTiO 3prepared using HClO 4-TiO 2and calcined at 900°C,the XRD patterns are almost identical irrespective of Ba/Ti ratio and cubic phase is observed.However,tetragonal phase was observed at 2θ)45°for the powders synthesized at Ba/Ti ratios of 1.2,1.4,1.6,1.8,and 2.0and calcined at 1150°C for 2h,as shown in Figure 2b.A slight increase in the intensity of tetragonal phase with Ba/Ti ratio may be due to the removal of barium vacancies (charge compensator of OH -defect)by excess barium content,which stabilizes tetragonality.Figures 3and 4show the SEM pictures of BaTiO 3samples prepared using HCl-TiO 2and HClO 4-TiO 2,respectively,at various Ba/Ti ratios of 1.2,1.4,1.6,and 1.8.The particles agglomerated in a spherical shape with ca.0.05-0.15µm (ca.50-150nm)diameters.A possible mechanism for the formation of BaTiO 3by hydrothermal synthesis is the dissolution-Figure 2.XRD patterns of BaTiO 3synthesized at various Ba/Ti ratios using (a)HCl-TiO 2and (b)HClO 4-TiO 2precursors and calcined at 1150°C (2h).Figure 3.SEM micrographs of as-synthesized BaTiO 3prepared using HCl-TiO 2at various Ba/Ti ratios:(a)1.2,(b)1.4,(c)1.6,and (d)1.8.1870Ind.Eng.Chem.Res.,Vol.47,No.6,2008precipitation method,38in which there is a chemical equilibrium between TiO 2and [Ti(OH)x ]4-x .[Ti(OH)x ]4-x ,which is a highly active species,can combine with Ba 2+to form a new nucleus,and hence,with an increase in Ba/Ti ratio the chance for the formation of a new nucleus by [Ti(OH)x ]4-x increases and leads to a decrease in the particle size of BaTiO 3.Figure 3shows the decrease in the particle size of BaTiO 3with an increase in Ba/Ti ratio,which is in accord with the dissolution -precipitation mechanism.TEM results show that the primary particles of the sample prepared at Ba/Ti ratios of 1.2and 1.4using HCl-TiO 2as precursor are spherical in shape with 50-60nm diameters,as shown in Figure 5a,b,whereas the particle sizes of BaTiO 3prepared using HClO 4-TiO 2are in the range of 40-50nm diameters (Figure 5c,d).Moreover,it can be ascertained from TEM images that the Ba/Ti ratio increases the cluster size of primary particles.Besides,it should be noted that the stability of cubic and tetragonal phases depends on the critical size of BaTiO 3particles and the critical size was reported to be ∼50nm.39The crystallite size of BaTiO 3is a principal factor controlling tetragonality because the surface defects of nanoc-rystallites are predominant over the bulk ones below a certain critical size of BaTiO 3.The surface defects can prevent the completion of phase transformation,leading to high strains within the crystal.Increase in the cluster size of primary particles reduces the strain within the cubic structure for distortion.It can be concluded that the phase transition of cubic BaTiO 3occurs at 1150°C irrespective of Ba/Ti ratio when HClO 4-TiO 2was used as the TiO 2precursor.Moreover,the primaryparticleFigure 4.SEM micrographs of as-synthesized BaTiO 3prepared using HClO 4-TiO 2at various Ba/Ti ratios:(a)1.2,(b)1.4,(c)1.6,and (d)1.8.Figure 5.TEM micrographs of BaTiO 3prepared using (a)HCl-TiO 2,Ba/Ti )1.2;(b)HCl-TiO 2,Ba/Ti )1.4;(c)HClO 4-TiO 2,Ba/Ti )1.2;and (d)HClO 4-TiO 2,Ba/Ti )1.4.Figure 6.XRD patterns of BaTiO 3synthesized at various temperatures using (a)HCl-TiO 2and (b)HClO 4-TiO 2precursors calcined at 900°C (2h).Ind.Eng.Chem.Res.,Vol.47,No.6,20081871size of BaTiO 3prepared using HClO 4-TiO 2is smaller than that prepared using HCl-TiO 2,which can be ascribed to the smaller particle size of TiO 2prepared by HClO 4.34The agglomeration of BaTiO 3nanoparticles at higher calcination temperature promotes the stability of the tetragonal phase.3.2.Effect of Synthesis Temperature.To study the influence of synthesis temperature on the phase of BaTiO 3and particle morphology,BaTiO 3was prepared at 80,120,160,180,and 200°C while keeping the rest of the process parameters as Ba/Ti )1.2and the synthesis time as 6h.The XRD patterns of BaTiO 3obtained at different reaction temperatures and calcined at 900°C are given in Figure 6.The XRD results illustrated well-developed cubic crystalline phase and the intensity of the peaks increased with reaction temperature.There is a possibility of decrease in the unit-cell volume and decrease in density with an increase in the reaction temperature due to the release of lattice hydroxyls.20The influence of calcination temperature withsynthesis temperature is compiled in Table 2.Figure 7depicts the XRD patterns of BaTiO 3calcined at 1150°C.With increased synthesis temperature,the diffraction peaks related to the (200)and (002)planes of the tetragonal BaTiO 3separated and the c /a ratio of the lattice increased,confirming the cubic -tetragonal phase transition with synthesis temperature.The splitting of the (200)reflection is apparent for the samples synthesized at 180and 200°C,suggesting the tetragonal phase.The intensity ratio of 45°peaks significantly increased as the synthesis temperature increased.The presence of shoulders at 80and 120°C represents the formation of partially tetragonal phase in cubic BaTiO 3.The stabilization of tetragonal phase with increase in temperature may be due to the removal of hydroxyl groups in the BaTiO 3lattice.Figure 8depicts the SEM micrographs of BaTiO 3prepared using HCl-TiO 2at 80,120,180,and 200°C for 24h.The particles agglomerated into a spherical shape,and the particle sizes estimated from the SEM micrographs are within 0.05-0.15µm in diameter.When the synthesis temperature increased from 80to 200°C and with reacting for 24h,the particle size of BaTiO 3increased to 0.09-0.15µm.The shape of the particles was observed to be spherical independent of treated tempera-tures.The increase in the synthesis temperature leads to an increase in the particle size,which may explain the stronger agglomeration at higher temperature.However,for BaTiO 3prepared using HClO 4-TiO 2(Figure 9),the secondary particle size increased from 0.05to 0.10µm with an increase in the reaction temperature from 80to 200°C for 24h,confirming that the particle size of BaTiO 3was dependent on synthesis temperature.The overall shape of the agglomerated secondary particle size was estimated to be 0.05-0.10µm in diameter.As shown in Figure 10,the particles consist of near-monodis-perse spherical nanoparticles of BaTiO 3.The agglomeration of primary particles with an increase in the reaction temperature can be identified from TEM images,as shown in Figure 10.The clusters of primary particles observed for HClO 4-TiO 2precursor are more than those of HCl-TiO 2.This result suggested that the crystallite size is one of the vital factors that control tetragonality.At a higher reaction temperature,the phase transition has occurred from cubic to tetragonal.3.3.Effect of Calcination Temperature.The stability of the cubic phase in BaTiO 3prepared by hydrothermal synthesis at room temperature may be accounted for by the presence of weakly bound water molecules absorbed onto the surface of the particles and the more strongly bonded structural water as lattice OH -ions.The content of barium vacancy as well as OH -defects in the cubic crystallites is higher than that inTable 2.Effect of Synthesis Temperature and Calcination Temperature on the Crystalline Phase of BaTiO 3calcination temp (°C)Ti precursor Ba/Ti ratio synthesis temp (°C)synthesis time (h)9001150crystalline phase HCl-TiO 21.2806--cubic 1.21206--cubic 1.21606--cubic 1.21806--cubic 1.22006--cubic HClO 4-TiO 21.2806--cubic 1.21206--cubic 1.21606--cubic 1.21806--cubic 1.22006--cubic HCl-TiO 21.2806yes -cubic 1.21206yes -cubic 1.21606yes -cubic 1.21806yes -cubic 1.22006yes -cubic HClO 4-TiO 21.2806yes -cubic 1.21206yes -cubic 1.21606yes -cubic 1.21806yes -cubic 1.22006yes -cubic HCl-TiO 21.2806-yes cubic 1.21206-yes cubic 1.21606-yes cubic 1.21806-yes tetragonal 1.22006-yes tetragonal HClO 4-TiO 21.2806-yes cubic 1.21206-yes cubic 1.21606-yes tetragonal 1.21806-yes tetragonal 1.22006-yestetragonalFigure 7.XRD patterns of BaTiO 3synthesized (Ba/Ti )1.2)at various temperatures using (a)HCl-TiO 2and (b)HClO 4-TiO 2precursors and calcined at 1150°C (2h).1872Ind.Eng.Chem.Res.,Vol.47,No.6,2008tetragonal phase.The cubic -tetragonal phase transformation at higher reaction temperature and calcination temperature is due to the elimination of OH -vacancies from the lattice with heat treatment,which leads to the tetragonal stability.At the Curie point,where BaTiO 3undergoes a phase transition,the relative displacement of cation sublattice to O 2-sublattice causes the phase transition of BaTiO 3from cubic to tetragonal.The oxygen vacancies have significant mobility above 650°C,whereas the cation vacancies acquire measurable mobility only above 1050°C.24Moreover,the decrease in the lattice parameter of the crystallites with temperature led to the conclusion that the removal of OH -defects caused the enlargement of the unit cell and released the lattice strain to form the tetragonal phase.3.4.Effect of Synthesis Time.The effect of synthesis time on the formation of crystalline BaTiO 3was also studied by performing the experiments at different reaction times ranging from 3to 24h at 160°C with Ba/Ti )1.2.The crystalline form at shorter periods of time,viz.,3and 6h,is primarily the metastable cubic form.SEM micrographs indicated no signifi-cant difference in the morphology.The cluster size was larger by extending the processing time,but the particle size has no significant difference.BaTiO 3powders prepared by using HClO 4-TiO 2as the precursor resulted similarly to those prepared by using HCl-TiO 2as the precursor.The XRD patterns as shown in Figure 11confirm the cubic phase of BaTiO 3prepared using HCl-TiO 2and HClO 4-TiO 2calcined at 900°C.Figure 12a shows the typical phase transformation of BaTiO 3prepared using HCl-TiO 2.When BaTiO 3prepared using HCl-TiO 2was treated for 12h,a noticeable peak splitting appeared.With increasing reaction time from 12to 24h,the intensity and sharpness of the tetragonal peak splitting increased,indicating an increase in the crystallinity of the tetragonal phase along with anincreaseFigure 8.SEM micrographs of BaTiO 3synthesized using HCl-TiO 2at various temperatures:(a)80,(b)120,(c)180,and (d)200°C.Figure 9.SEM micrographs of BaTiO 3synthesized using HClO 4-TiO 2at various temperatures:(a)80,(b)120,(c)180,and (d)200°C.Figure 10.TEM micrographs of BaTiO 3prepared using (a)HCl-TiO 2,120°C;(b)HCl-TiO 2,180°C;(c)HClO 4-TiO 2,120°C;and (d)HClO 4-TiO 2,180°C.Ind.Eng.Chem.Res.,Vol.47,No.6,20081873in the particle size of BaTiO 3.The results are summarized in Table 3.The tetragonal BaTiO 3can be synthesized from HCl-TiO 2at reaction times of 12and 24h using Ba/Ti ratio of 1.2,synthesis temperature of 160°C,and calcination temperature at 1150°C for 2h.However,even at 3h reaction time,BaTiO 3prepared using HClO 4-TiO 2achieved the cubic -tetragonal phase transformation (Figure 12b).The reason can be ascribed to the acidic nature of HClO 4,which leads to the formation of BaTiO 3with fewer defects so as to stabilize the tetragonal phase apart from the possible influence of Cl -ions present in the reaction mixture.The presence of chloride ions is speculated to influence the diffusion of Ba 2+ions and retard the crystal growth process,thereby stabilizing the tetragonal phase by forming larger crystals.40In the early stage of reaction,chloride ions produce more nuclei and form smaller particles,which grow larger at prolonged time.Sun and Li 41reported that BaTiO 3particles synthesized in the presence of chloride ions are slightly larger than the particles synthesized in the absence of chloride ions,however,with an enhanced tetragonality compared to the latter.The physicochemical properties of TiO 2prepared from HCl and HClO 4make the difference in the properties of BaTiO 3.34Therefore,it is concluded that the BaTiO 3tetragonal phase can be successfully synthesized using HClO 4-TiO 2as the precursor at a [H +]/[Ti 4+]ratio of 1.2,synthesis temperature of 160°C,and calcination temperature of 1150°C (2h).344.ConclusionIn the present study,the morphology and phase transformation of BaTiO 3prepared using HCl-TiO 2and HClO 4-TiO 2with respect to reaction temperature,reaction time,Ba/Ti ratio,and calcination time were investigated.Increase in Ba/Ti ratio,temperature,and reaction time increases the possibility of cubic phase transformations.Well-crystallized tetragonal BaTiO 3powders of high purity were obtained using HCl-TiO 2as the precursor at optimum conditions of Ba/Ti ratio )1.2,temper-Figure 11.XRD patterns of BaTiO 3synthesized at various reaction times using (a)HCl-TiO 2and (b)HClO 4-TiO 2precursors calcined at 900°C (2h).Figure 12.XRD patterns of BaTiO 3synthesized at various reaction times using (a)HCl-TiO 2and (b)HClO 4-TiO 2precursors.Conditions:reaction temperature )160°C;Ba/Ti )1.2;calcination temperature )1150°C (2h).Table 3.Effect of Synthesis Time and Calcination Temperature on the Crystalline Phase of BaTiO 3calcination temp (°C)Ti precursor Ba/Ti ratio synthesis temp (°C)synthesis time (h)9001150crystalline phase HCl-TiO 21.21603--cubic 1.21606--cubic 1.216012--cubic 1.216024--cubic HClO 4-TiO 21.21603--cubic 1.21606--cubic 1.216012--cubic 1.216024--cubic HCl-TiO 21.21603yes -cubic 1.21606yes -cubic 1.216012yes -cubic 1.216024yes -cubic HClO 4-TiO 21.21603yes -cubic 1.21606yes -cubic 1.216012yes -cubic 1.216024yes -cubic HCl-TiO 21.21603-yes cubic 1.21606-yes cubic 1.216012-yes tetragonal 1.216024-yes tetragonal HClO 4-TiO 21.21603-yes tetragonal 1.21606-yes tetragonal 1.216012-yes tetragonal 1.216024-yestetragonal1874Ind.Eng.Chem.Res.,Vol.47,No.6,2008ature)180°C,synthesis time)6h,and calcination at 1150°C for2h.However,the phase transformation of BaTiO3 prepared using HClO4-TiO2occurred at lower reaction temper-ature(160°C)and synthesis time(3h)than BaTiO3particles prepared using HCl-TiO2.BaTiO3particles are agglomerated to a spherical shape with ca.80-90nm and BaTiO3particles synthesized with HClO4-TiO2were smaller than those prepared by HCl-TiO2.The stabilization of cubic BaTiO3is caused by defects including OH-defects and barium vacancies.The formation of tetragonal BaTiO3is promoted by the use of high reaction temperature,calcination temperature,and reaction time, which reduces the probability of forming OH-vacancies.In summary,the precursor has a strong influence on the size and morphology of BaTiO3.BaTiO3prepared from HClO4-TiO2 indeed increases the transformation of cubic-to-tetragonal phase at lower reaction conditions without significant particle growth. 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Soc.1994,77,3186.(30)Kajiyoshi,K.;Ishizawa,N.;Yoshimura,M.Preparation of tetragonal barium titanate thin film on titanium metal substrate by hydrothermal method.J.Am.Ceram.Soc.1991,74,369.(31)Takeuchi,T.;Ado,K.;Asai,T.;Kageyama,H.;Saito,T.; Masquelier,C.;Nakamura,O.Thickness surface phase of barium titanate single-crystalline grains.J.Am.Ceram.Soc.1994,77,1665.(32)Li,X.;Shih,W.H.Size effects in barium titanate particles and clusters.J.Am.Ceram.Soc.1997,80,2844.(33)Henninga,D.;Schreinemacher,S.Characterization of hydrothermal barium titanate.J.Eur.Ceram.Soc.1992,9,41.(34)Rajesh, B.;Sasirekha,N.R.;Chen,Y.-W.Influence of acid precursors on physicochemical properties of nanosized titania synthesized by thermal-hydrolysis method.Mater.Res.Bull.2008,43,682.(35)Bai,W.;Choy,K.L.;Sytelzer,N.H.J.;Schoonman,J.Thermo-phoresis-assisted vapour phase synthesis of CeO2and Ce x Y1-x O2-δnano-particles.Solid State Ionics1999,116,225.(36)Shi,E.W.;Xia,C.T.;Zhong,W.Z.;Wang,B.G.;Feng,C.D. Crystallographic properties of hydrothermal barium titanate crystallites.J. Am.Ceram.Soc.1997,80,1567.(37)Atkins,P.W.Physical Chemistry,5th ed.;W.H.Freeman and Company:New York,1994.(38)Chen,K.Y.;Chen,Y.-W.Preparation of barium titanate ultrafine particles from rutile titania by a hydrothermal conversion.Powder Technol. 2004,141,69.(39)Ishikawa,K.;Yoshikawa,K.;Okada,N.Size effect on the ferroelectric phase transition in PbTiO3ultrafine particles.Phys.Re V.B 1998,37,5852.(40)Dutta,P.K.;Gregg,J.R.Hydrothermal synthesis of tetragonal barium titanate.Chem.Mater.1992,4,843.(41)Sun,W.;Li,J.Microwave-hydrothermal synthesis of tetragonal barium titanate.Mater.Lett.2006,60,1599.Recei V ed for re V iew July20,2007Re V ised manuscript recei V ed November30,2007Accepted December23,2007IE070986M Ind.Eng.Chem.Res.,Vol.47,No.6,20081875。

微波水热法制备钛酸锶钡粉体的研究进展

介电和光学性能在Ｂ／ｒａＳ物质的量比为Ｏ１的范围内连续调节，在电子元件的应用领域里具有非常重～这
要的意义口．是一种优良的热敏材料、］它电容器材料和铁电、电材料，压具有高介电常数、介电损耗、低居里温度（Ｃ）Ｔ随组成改变以及介电常数随电场非线性变化等特点，超大规模动态存储器、波调谐器等领在微域具有广阔的应用前景，为集成器件领域最广泛研究的材料之一［．成２］目前，细钛酸锶钡的制备方法主要有高温固相烧结法，胶凝一法和共沉淀法等＿．统制备工超溶胶＿传３］艺＿］４是通过热传导加热的方式使氧化物分解然后形成钙钛矿结构，致合成温度较高（０导１１０℃ ）晶粒、较大、组份不够均匀而影响了成瓷晶粒的均匀性．胶一胶法和共沉淀等湿化学方法可以获得粒径较小溶凝且均匀的粉体，是大部分容易产生团聚，而影响了其使用］但从．微波水热法是近几年才在国际上开展研究的一种纳米粉体制备新方法，常规水热法相比，与具有反应温度更低、反应时间更短的优点，使最终产物出现新相，备出结晶完好、径分布均匀的粉体］该并制粒．方法在水热合成方法的基础上把两种技术有效结合起来，以大大缩短水热合成的时间，提高生产效率，可降低合成温度，节约能耗。．国Ｐｎｓｌａｉ。美］ｅｎｙｖｎａ大学较早采用微波水热法制备了一些陶瓷及金属粉体，目前印度的ＳＢＤｅｈａｄ＿等人应用微波水热合成法制备出了粒径为２０ｎ的ＢＴ粉体，．．ｓｐｎｅ８０ｍＳ但粒径较粗，难以获得致密陶瓷，外关于微波水热反应的机理尚在探索中．此

水热法制备钛酸钡的工艺流程

水热法制备钛酸钡的工艺流程下载温馨提示：该文档是我店铺精心编制而成，希望大家下载以后，能够帮助大家解决实际的问题。

文档下载后可定制随意修改，请根据实际需要进行相应的调整和使用，谢谢!并且，本店铺为大家提供各种各样类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，如想了解不同资料格式和写法，敬请关注!Download tips: This document is carefully compiled by the editor. I hope that after you download them, they can help yousolve practical problems. The document can be customized and modified after downloading, please adjust and use it according to actual needs, thank you!In addition, our shop provides you with various types of practical materials, such as educational essays, diary appreciation, sentence excerpts, ancient poems, classic articles, topic composition, work summary, word parsing, copy excerpts,other materials and so on, want to know different data formats and writing methods, please pay attention!钛酸钡是一种重要的无机化合物，具有许多重要的应用价值。

室温研磨-微波加热合成钛酸钡纳米粒子

绝缘性能，被广泛应用于制作自动控温发热元件、多层陶瓷电容器、非线性光学器件、外线热像仪、电响红压应扫描探针显微镜、态随机存取存贮器和其它光电动器件［。随着现代科学技术的发展，ａ０１］ＢＴｉ３的用途将会越来越广泛。钛酸钡粉体的制备方法有【３：高温固相煅烧法、学共沉淀法、胶一胶法、热化溶凝水法、微乳液法、喷雾热解法等，这些方法存在以下一但些缺点：高温固相煅烧法反应温度高（００１０ ℃）１０￣２０，反应活性差，到的粉体硬团聚严重、度低、粒大得纯颗而粒度分布宽，学共沉淀法反应活性虽有所提高，化但仍需较高的煅烧温度，而与高温固相煅烧法存在一因些同样的缺点，溶胶一凝胶法煅烧温度也较高、艺复工杂，产品粒子团聚严重；热法需高压生产设备，乳水微液法需大量的有机溶剂，量低、经济，对环境污产不且染严重；喷雾热解法产物中含有空心或破壳粒子、份组分布不均匀、备复杂。然而，１６设自９７年ｗｉｉｍｓｌａ发ｌ现微波能促进某些化学反应以来，波辐射技术用于微纳米材料的制备受到人们的普遍关注。与传统的加热方法相比，波加热具有加热速度快、热均匀、温微加无度梯度、无滞后效应等特点，它是一种内加热。微波且对化学反应还具有催化作用，能改变化学反应的途它径，降低反应温度［１，因而近年来，用微波技术制利备钛酸钡受到了人们的重视，Ｆｉｎｒ等Ｄ］Ｂ — 如ｅｇｅｓ用ａ

钛酸钡的制备工艺以及制备方法

1 前言钛酸钡是电子陶瓷材料的基础原料，被称为电子陶瓷业的支柱。

它具有高介电常数、低介电损耗、优良的铁电、压电、耐压和绝缘性能，被广泛的应用于制造陶瓷敏感元件，尤其是正温度系数热敏电阻(PTC)、多层陶瓷电容器(MLCCS)、热电元件、压电陶瓷、声纳、红外辐射探测元件、晶体陶瓷电容器、电光显示板、记忆材料、聚合物基复合材料以及涂层等。

钛酸钡具有钙钛矿晶体结构，用于制造电子陶瓷材料的粉体粒径一般要求在100nm以内。

因此BaTiO3粉体粒度、形貌的研究一直是国内外关注的焦点。

钛酸钡粉体制备方法有很多，如固相法、化学沉淀法、溶胶—凝胶法、水热法、超声波合成法等。

最近几年制备技术得到了快速发展，本文综述了国内外具有代表性的钛酸钡粉体的合成方法，并在此基础上提出了研究展望。

2 钛酸钡粉体的制备工艺2.1 固相合成法固相法是钛酸钡粉体的传统制备方法，典型的工艺是将等量碳酸钡和二氧化钛混合，在1 500℃温度下反应24h，反应式为：BaCO3+TiO2→BaTiO3+CO2↑。

该法工艺简单，设备可靠。

但由于是在高温下完成固相间的扩散传质，故所得BaTiO3粉体粒径比较大(微米)，必须再次进行球磨。

高温煅烧能耗较大，化学成分不均匀，影响烧结陶瓷的性能，团聚现象严重，较难得到纯BaTiO3晶相，粉体纯度低，原料成本较高。

一般只用于制作技术性能要求较低的产品。

2.2化学沉淀法2.2.1 直接沉淀法在金属盐溶液中加入适当的沉淀剂，控制适当的条件使沉淀剂与金属离子反应生成陶瓷粉体沉淀物团。

如将Ba(OC3H7)2和Ti(OC5H11)4溶于异丙醇中，加水分解产物可得沉淀的BaTiO3粉体。

该法工艺简单，在常压下进行，不需高温，反应条件温和，易控制，原料成本低，但容易引入BaCO3、TiO2等杂质，且粒度分布宽，需进行后处理。

2.2.2 草酸盐共沉淀法将精制的TiCl4和BaCl2的水溶液混合，在一定条件下以一定速度滴加到草酸溶液中，同时加入表面活性剂，不断搅拌即得到BaTiO3的前驱体草酸氧钛钡沉淀BaTiO(C2O4)4·4H2O(BTO)。

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第 0 卷
第1期
内蒙古民族大学学报
自然科学版
Vol.20
NO.1
2005 年 2 月
Journal of lnner Mongolia University for Nationalities
Feb.2005
微波 ! 水热法制备钛酸钡纳米晶
付乌有，哈日巴拉
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（7 ，，），最大功率（DE ）为.( 微波 . ’ ( 仪器整个合成是在微波炉 ;9 / < 3 = ;7 0 > ; " ? @ A B C : 7 " F * *D， , 频率为( ，类似于家用微波炉’ 反应釜整体采用双层结构，内釜采用聚四氟乙烯（I 制造，外釜 ’ ) 3G H # J =）采用以橡胶分子为主链的接枝共聚物与树脂的复合物，为任性塑料’ 然后将 * . ’ & 方法将* ’ .E 0 8: " % - 溶解在. *E 8二次蒸馏水并倒入上述双层反应釜， ’ * * (E 0 8的氯化钡及相同数量的(; 氯化钛一并加入上述反应体系中，反应体系 , ，强烈搅拌 & ， - 值调解至 " . & *E $ K 拧紧盖儿，将反应釜放入微波炉内，温度调至5 不到 &E 继续反应 & * ! . 5 * +范围， $ K即可达到反应温度’ 将沉淀离心分离并用二次蒸馏水洗涤数次，最后将粉体在3 ! 3@之后取出， * +真空干燥. *@ ’ ／ . ’ ) 产品表征与性能测试钛酸钡粉体平均晶粒尺寸及晶相结构采用日本理学 L E " F 6& 7 型 M6 > " 1 衍射仪测定，粉体热失重分析采用美国 ; ／ 7 N O " * ’ . 3 ) . 4K E’ A ? ? 8 A ># 0 8 A P 0公司 # G 9 < L # 9 4 3 . A型差热6 热失重分析仪，升温速度. ／，气氛为静态空气；用透射电镜（观察所制备粉 *+ E $ K Q = % R， Q = ;6. ( * * = M）用S （电感、电容、电阻）测量仪测量样品的介电常数’ 末的晶粒尺寸及形貌观测’ R 3智能 R 7 /
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图.为. 从图 . 中可看出钛酸钡在 ( （. 、 5 * + 条件下制备的样品 M6> " . ’ 2 3 U * *） & . ’ & 5 U 1 衍射图’ （）、（）、（）、（） . . * & 4 ’ 5 * U. . . ) ) ’ 4 3 U( * * 3 * ’ ) 3 U( . *’ 等衍射角度处的特征峰已明显出现，它与立方相 ! （）一致’ 因此确 " # $ % Q 7 I L <标准卡， : 0 ’ V 3 6 * ( . ) ( & 定水热6微波法得到的 ! 但也存在很微弱的 ! 说明 ! " # $ % " 7 % " # $ % ( & 粉体为立方相’ & 的特征峰， ( & 晶体中含有少量 ! 随着制备温度的升高，所含 ! 但不能完全消失’ 这是因为空气中 7 " 7 % " 7 % % &， & 的量减少， (与体系中 ! （% 不同温度制备得到的样品相分析结果列表 . 中’ 笔者认为微波 6 水热法制备 " -） ( 反应所至’ 纳米立方相 ! " # $ % 5 * +’ & 的最适宜温度是. 万方数据
〔，〕 8 # 现代科学技术的发展要求陶瓷料粉具有高纯、超细（纳米级）、粒径分布窄等特性. 料 . ) * + , & 粉体尺寸
的大小、分布状况、晶体结构等直接影响功能陶瓷的性能. 当粉体颗粒尺寸达到纳米级时，材料的性能将发生很大的变化，因此，制备均一、细小的 ) 目前工业上常 * + , &粉体是提高功能陶瓷性能的主要途径之一.
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〔〕 & 由于该方法使〔) （E 的方法来制备 ) 用煅烧 ) . , * + , * + , * E &和+ # 或草酸氧钛钡 # %） #〕 & 的粉体材料
用高达8" 使得到的粉体硬团聚严重、表面活性差，即使经过反复焙烧研磨，也只 " " 9! 8# " " 9的温度，能达到微米级粉体.
： : 4 . & " % , & N * : B O 1 J K * D D , : F) * + , * JQ 1 F * 1 F RA J , : , O 1 B P * M F !I R 1 B K I F 1 ; * D; F K I B R . + I F 2 Q G*; 2 &P （+ 、 O 1 J K * D D , : FJ K 1 A O K A 1 FP * J, : M F J K , * K F RC 1 * : J ; , J J , B :F D F O K 1 B :; , O 1 B 1 * I J / ’） 0!1 * 2 G 2K G Q 2 ：K R , H H 1 * O K , B :* : RK I F 1 ; B 1 * M , ; F K 1 , O* : * D J , J . + I F1 F J A D K, : R , O * K , B : I FO A C , OQ I * J F) * + , G 2 & （ : * : B O 1 J K * D * :* M F 1 * FQ * 1 K , O D F J * C B A K # 7: ;） P * J B C K * , : F RM , *’!(; F K I B R * K D B PK F ; F 1 * K A 1 F 2 G Q （ 7 " ! 8 7 " 9） . + I F F S F 1 , ; F : K * D 1 F J A D K J B H R , F D F O K 1 , O 1 B F 1 K , F J B H : * : B O 1 J K * D , : R , O * K F K I * K K I F R , T Q Q Q 2 ， F D F O K 1 , O O B : J K * : K " B H : * : B O 1 J K * D , J; A O I D * 1 F 1 K I * : K I * K B H C A D U; * K F 1 , * D J P , K I 1 F R A O , : B H 1 * , : 2 G G G ，， J , V F K I F " B H : * : B O 1 J K * D D , : F; * K F 1 , * D , : O 1 F * J F J H , 1 J K * : R K I F : , K H * D D J K B J ; * D D F 1 M * D A F . 2 ：；；； ; # ( " 9 . ’ , O 1 B P * M F !I R 1 B K I F 1 ; * D; F K I B R N * : B O 1 J K * D ) * 1 , A ;K , K * : * K F 4 , F D F O K 1 , OQ 1 B F 1 K , F J 2 2 Q -6 钛酸钡（) 属于典型的钙钛矿（6 结构，具有高介电常数及优良的铁电、压电和绝缘性能，是 * + , ) &） &）其掺杂固溶体在电子陶瓷工业中有着广泛的应用，在高性能 W 重要的电子陶瓷、 W + E 陶瓷原料. + E 热敏半导体陶瓷材料、晶界陶瓷电容器、独石多层陶瓷电容器微波介质材料等器件制造中作主要基体原