XRD简介(英文)

Optical related technology

X-ray Diffraction

Abstract

:X-ray diffraction (XRD) technology is widely used in materials characterization. Identify

chemistry constituents of the product, analyze the space group, lattice parameter and etc. In this

article, I will introduce the principle of XRDincluding the diffractometer and simple application with

the XRD pattern.

Introduction

1.

X-ray

is a kind of electromagnetic radiation generated by the inner electron transition. Its wavelength

ranging from 0.01 to 10nm. X-ray photons with a short wavelength (below 0.2nm) have the energies

above

5keV.

Therefore

comes

the

penetrating

ability

[1].

Moreover,

X-ray

interact

with

matter

and

project the matter’s information in X

-ray diffraction result, X-ray are widely used to image

the

inside

of

the

object

and

is

thought

highly

in

the

field

medical

radiography

and

material

characterization.

2.

X-ray diffraction

is an interaction between X-ray and matter.

Consider the materialas lattice as show at

figure 1

. Consider the

situation

as

what

we

had

learned-the

Rayleigh

scattering.

In

some direction, we

can detect the interference of two narrow

X-ray

beams,

and

constructive

interference

meet

the

optical

path difference:

2dsin

θ

=

n

λ

(n

=

0,1,2

…

)

< br>.

Kwon

as

the

Bragg

’

s

law.

d

is

the

distance

between

two

particles,

θ

is

the

angle

between

incident

X-ray

and

lattice

plane,

λ

is

the

wavelength

of

can

learn

from

the

equation

that

the

constructive

interonly

happen

in

some

particular

angle

since

the

wavelength

and

the

distance(consider as the

grating constant) are fixed

for one material, and for the three dimensional

world we have three constant marked as (h k l) to describe the space group. Nevertheless, is hard to

directly

detect

the

3D

pattern,

instead,

we

introduce

the

spherical

projection

pattern

and

develop

some

mathematical

translation

to

restructure

the

3D

condition

shows

at

figure

2

.

We

can

learn

the

direction

and

distance

from

the

spherical

coordinate.

Let

’s

go

over

the

procedure

of

XRD.

First

we

shot

a

X-ray

to

the

sample and get its diffraction pattern and read

the information from the 2D pattern[2].

3.

X-ray Diffractometer

is high integration optical apparatus shows at

figure 3

. The X-ray source usually

chooses

Cu

as

target

material

applying hot

electrons

which

accelerated

by

high

voltage

and

generate

X-ray

[3].

Sample

platform

and

detector

link

together

and

rotate

along

the

horizontal spherical center axis. We can also have the sample

platform

and

detector

fixed

and

rotate

the

X-ray

gun.

We

introduce

the

concept

of

resolution

to

evaluate

the

quality

of

the

X-ray

Diffractometer.

A

strong

and

stable

X-ray

generator is necessary. The other condition is the minimum

angle

which

the

machine

can

stable

rotate.

The

resolution

usually

plays

an

important

role

in

quantifying

analysis

such

as

determine

the

doping

ratio

by

measure

the

XRD

peak

offset.