You can't see the central spot, so will struggle to measure any distances. You really need a double exposure so you can see the zero diffraction spot. You would then measure the distance of each spot or ring from that central spot. Spots are due to diffraction from a single crystal, and you can identify the zone axis for these patterns. Rings are due to multiple crystals. This looks like you have a few crystals that have formed this pattern, as there is a combination of spots and rings.

Using Bragg's equation

[n(lambda)=2sin(theta]

you can convert the measurements to d spacings. It is easier to rearrange this to

d=(lamda)l/r,

where d is the lattice spacing, lambda the wavelength of the electrons, l is the camera focal length and r is the distance between the central spot and the diffracted spot or ring. You can set the scale in a program like ImageJ and measure the distances using this free program.

You need to find these values from the TEM operator or manual for the TEM you used to convert the pattern to d spacings. Then you need to compare the values you measure to standard crystallographic diffraction patterns to identify your material. It helps if you have an idea what your material is so you know which patterns to compare your material to.

We did it for magnetite in this paper (in the supplimentary information)

You can't see the central spot, so will struggle to measure any distances. You really need a double exposure so you can see the zero diffraction spot. You would then measure the distance of each spot or ring from that central spot. Spots are due to diffraction from a single crystal, and you can identify the zone axis for these patterns. Rings are due to multiple crystals. This looks like you have a few crystals that have formed this pattern, as there is a combination of spots and rings.

Using Bragg's equation

[n(lambda)=2sin(theta]

you can convert the measurements to d spacings. It is easier to rearrange this to

d=(lamda)l/r,

where d is the lattice spacing, lambda the wavelength of the electrons, l is the camera focal length and r is the distance between the central spot and the diffracted spot or ring. You can set the scale in a program like ImageJ and measure the distances using this free program.

You need to find these values from the TEM operator or manual for the TEM you used to convert the pattern to d spacings. Then you need to compare the values you measure to standard crystallographic diffraction patterns to identify your material. It helps if you have an idea what your material is so you know which patterns to compare your material to.

We did it for magnetite in this paper (in the supplimentary information)

Sorry, Bragg's equation is n(lambda)=2dsin(theta). The d's fairly important :-)

As you are interested to analyze the SAD pattern.

go thorough the book "Practical electron microscopy in materials science by J.W. Edington" you will get some idea how to index the pattern.

As i could see from your SAD pattern that you have taken. It is not in well focused. try to take the images which is well focused, and then start indexing.

2     (1/nm)..........2*   1/(d/2)..............the value compare with jcpdf or, xpert high score

Yes...

as johanna Marie Galloway say

Maybe this link help you

https://code.google.com/p/diffraction-ring-profiler/wiki/howtoscreenshots

the image firstly show crystalline materials 

the curlicues is nearly clear

if you found spots in your pattern of electron beam that meaning that the material is crystalline

if each one ore two spots face each other its mean the plane of crystals and atoms

you can from the central spot to each edge measure the distance to see which plane you study and so on 

@V.M LENART , thanks for your nice link. i  have a little complication about GDIS text file , from where i can get this file for reference to use in this tool .

From the image you showed, your diffraction pattern is calibrated in reciprocal space. It mean you can determine the d-spacing (in reciprocal space) as the radius of the diffraction rings without caring about the central spot (don't try to record the central spot because it may burn your CCD camera). Then, d-spacing in real space can be calculated as 1/(reciprocal space d-spacing).

Hi, Debabrata,

Please refer to the following paper. It gives you enough information to analyze SAED patterns. Specifically, check the supplementary information for detailed calculations.

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