9 电子衍射谱标定原理和练习

5.6电子衍射谱标定练习

Ni 型正交相Al74.8Fe1.5Ni23.7的选区电子衍射花样图3.9 Al

3

Indexing of 2D patterns

Æ3D reciprocal lattice

Æ3D real lattice

Æorientation/phase identification

已知物质的d值计算

1、使用公式：立方系d=a/(h2 +k2 +l2)1/2

2、使用软件：Carine

3、查XRD标准粉末卡

Standard powder XRD data;

b) 查表标定法

利用软件计算出某种物质所有可能的衍射谱(R1+ R2=R3)与实验谱比较

reci.exe

fi2.dat

reci.exe

Fe3C, Cementite, Pnma, 5.0890, 6.7433, 4.5235

注意：滑移面消光！

Standard powder XRD data;

d1=d2

0.208

d3=

0.180

d4=

0.127

Use double tilting to determine directly a 3D reciprocal lattice

图3.4 六角相Al 5FeNi 的选区电子衍射花样

Figure 3.4 SAED patterns arranged in a stereo manner of the hexagonal Al 5FeNi phase.

For randomly orientated aggregates of polycrystals, the reciprocal lattice becomes a series of spheres.

The radii R i= Lλ/d i.

The number of points contributing to each sphere is known as the multiplicity.

典型非晶电子衍射

Powder patterns

图3.5 铸态合金Al 71Fe 5Ni 24的X 射线(λCuK = 0.15406 nm)衍射谱Figure 3.5 X-ray diffraction pattern of the as-cast Al 71Fe 5Ni 24alloy.

Ring patterns How to index a known powder pattern

1.Calculate the d list

2.Find out the indices for each peak How to index an unknown powder pattern

1.Survey the literature

2.Calculate the d list

pare with XRD cards

5.7 衍射图类型

•Spot (Selected area diffraction) •CBED (convergent beam) •Kikuchi (inelastic scattering) •HOLZ (high order Laue Zone) •Ring (multiple crystals) •Amorphous (diffuse rings)

Selected Area Electron Diffraction

Convergent Beam Electron Diffraction

Spots and CBED

Kikuchi line diffraction

Kikuchi lines