钛酸钡系铁电陶瓷的制备技术及性能研究

国内图书分类号：TM 22+3

硕士学位论文

题目：钛酸钡系铁电陶瓷的制备技术

及性能研究

硕士研究生：张培凤

导师：樊慧庆

申请学位级别：硕士

学科、专业：材料学

所在单位：材料学院

答辩日期：2008年3月

授予学位单位：西北工业大学

Classified index：TM22+3

Dissertation for Master’s Degree

PREPARATION AND CHARACTERIZATION OF BARIUM TITANATE BASED FERROELECTRIC

CERAMICS

Candidate: Peifeng Zhang

Advisor: Prof. Huiqing Fan

Specialty: Material Science

Subject: Material Science and Engineering

Northwestern Polytechnical University

March, 2008 • Xi’an

摘要

摘 要

钛酸钡（BaTiO3）是性能优异的强介电和铁电材料，被广泛应用于制造热敏电阻器、多层陶瓷电容器、电光器件和DRAM器件。自从20世纪40年代发现钛酸钡的优良的压电和介电性能以来，关于钛酸钡及掺杂钛酸钡的制备和介电性能的研究己成为一个热点领域。为了满足高性能介电材料的要求，关键之一就是要实现粉体原料的超细和均匀化，因此本文对BaTiO3系粉体及陶瓷进行了系统研究。

首先，采用水热法，以硝酸钡，二氧化钛，作为矿化剂的氢氧化钠为原料，在Ba/Ti摩尔比为1.6，矿化剂NaOH的浓度为3M，于180℃下水热反应16 h，获得了超细、高纯、高均匀性的立方相BaTiO3纳米粉体，并具体分析了Ba/Ti 摩尔比、反应时间和前驱物对粉体的影响。其次，采用溶胶-凝胶法制备Mg取代Ti的掺杂BaTiO3粉体，并分别于一系列温度下烧结成陶瓷（简称为SG-BMT），Mg的掺杂对陶瓷性能影响很大，纯BaTiO3中加入Mg后，其结构逐渐由四方相向立方相转变；同时，其介电常数、介电损耗降低，但稳定性大大增加；居里温度降低，并且居里峰展宽，出现明显的弥散现象。对于Mg掺杂BaTiO3陶瓷来讲，其可以取代Ti，也可以取代Ba，为进一步研究其不同的取代对制备的掺杂BaTiO3陶瓷的影响，采用传统固相法制备Mg取代Ba的掺杂BaTiO3陶瓷（简称为SS-BMT），其电学性能不如SG-BMT的好，介电常数较低，在最佳制备条件下仅1600，而SG-BMT高达2330，但居里温度下降的幅度不如SG-BMT大，其居里温度为93℃，SG-BMT为83℃。最后，采用传统固相法制备La掺杂BaTiO3陶瓷，发现其烧结温度升高到1450℃，电学性能也显著改善，其介电常数随着La含量的增大而减小，随烧结温度的升高则是先增大后减小，1450℃烧结得到的Ba0.98La0.02TiO3陶瓷性能最好，介电常数高达3515，损耗低至0.01，并且稳定性有较大提高，但居里温度降低至15℃以下。

关键词：钛酸钡，水热合成，掺杂工艺，介电性能

ABSTRACT

ABSTRACT

Barium titanate (BaTiO3) has been broadly used as the raw material for heat

variable resistor, multi-layer ceramicss capacitors, electro-optic devices and dynamic

random access memories. The research of preparation and properties of barium

titanate has been a focal point since the excellent dielectric properties of barium

titanate were discovered in 1940s. In order to meet the high-capacity need of

dielectric material, preparing symmetrical and little-size nanometer powders is the

sticking point, so lots of study has been done on BaTiO3 powders and ceramics.

Firstly, synthesis methods of pure BaTiO3 were probed to obtain excellent crafts

of powder preparation. In the hydrothermal experiment, Ba(NO3)2 and TiO2 were

used as precursors for barium and titanium respectively with NaOH as a mineralizer.

The perfect pure cubic BaTiO3 nano-powders were obtained by hydrothermal

℃

method at 180 for 16h with a 3M NaOH concentration from precursors at the

Ba/Ti molar ratio of 1.6. At last, how Ba/Ti molar ratio, holding time and precursors

influence the properties of BaTiO3 nano-powders have been studied.

Secondly, impurities have great influence on the properties of BaTiO3. The Mg

doped BaTiO3 powders have been prepared by sol-gel method with Mg substituent

Ti and then the Mg doped ceramics have been obtained through high temperature

sintering (SG-BMT for short). Comparing with BaTiO3 ceramics, the phase of Mg

doped BaTiO3 ceramics changed from tetragonal to cubic gradually; the dielectric

constant, dielectric loss and Curie temperature reduced, but the stability increased,

and the Curie peak began to broaden, appearing obvious dispersion. For Mg doped

BaTiO3 ceramics, Mg can replace Ti and replace Ba too, so the Mg doped BaTiO3

ceramics have been prepared by solid state method with Mg substituent Ba

(SS-BMT for short). Its best dielectric constant only 1600, but the SG-BMT could

℃ the achieve 2330; the Curie temperature of the SS-BMT reduced to 93 with

℃Lastly, The La doped BaTiO3 ceramics have been prepared by SG-BMT of 83.

solid state method with La substituent Ba. The sintering temperature increased to

℃3 ceramics; The dielectric constant 1450, which is higher than the pure BaTiO

firstly began to increase then reduced with the rising of sintering temperature and

reduced with the increase of La gradually; the Ba0.98La0.02TiO3 ceramics sintered at

℃dielectric properties with the dielectric constant of 3515, 1450 showed the best

dielectric loss of 0.01 and the better stability; the Curie temperature reduced so

greatly that it has reduced below 15℃.

Key Words: barium titanate, hydrothermal synthesis, doping process, dielectric

properties