Hi there,

Here I explain the step-by-step method to index the SAED patter

(i) Measure the diameter, 2R, of each ring using some image processing software such as Image tool, for example. Let's say for the first ring, the 2R = 5.37 [1/nm]

(ii) Obtain the value of radius, R, (w.r.t central spot); R= 2.68 [1/nm], the unit 1/nm means the distance is in reciprocal lattice

(iii) Obtain the interplanar distance (d), in real space, as 1/R; in our case d= 1/R = 1/2.68 =0.372 nm. note that the unit is nm now, as we are talking about real space.

Let us consider my sample to be TiO2, I know (by comparsion with d-value of different phases in literature) that a d-value of 0.372 correspond to (101) plan of anatase TiO2.

(iv) Now you found the d value for 1 ring. Do the same for procedure to obtain d-values for other rings.

(v) compare the d-value (each of which correspond to a certain set of hkl indices) with the the diffraction data from literature (and you know what is the compositi

on of your sample), for example from http://rruff.geo.arizona.edu/AMS/amcsd.php

or ICSD data base.

My advice to see a book under title  " Physical Principles of Electron Microscopy by F. Egerton" for more information for your question 

Regards, 

Thanks Yousif