When you collect a pattern with a non monochromatized radiation (Cu Kalpha1 and Cu Kalpha2) the effect is to see two peaks at two near angles but with an halved intensity for that of Ka2. This effect is particularly evident at high angle and for sinterized material (with large crystallite sizes). In this case this rule is not respected and not all the peaks seem doubled. It could be a structural distortion of your material (is it cubic)? Or the presence of impurities structurally similar to the main phase? Can you share some information about your material?
I agree with Marcella. Lets assume that the diffraction pattern was collected at a diffractometer with CuKalpha you will have wave lengths 1.54056 and 1.54439 Angstroem. From Braggs law: lambda = 2 d_hkl sin(theta) you can quickly calculate that the separation in 2Theta between the Kalpha_1 and K_alpha_2 peak will systematically increase with increasing 2Theta and be essentially non-detectable for 2Theta less than say 25 degrees.
For your sample, the splitting increases with increasing 2Theta, yet the first and 3rd reflection do not show any split at all. As you have few reflection over a range of 15(?) to roughly 70(?) 2Theta, your sample seems to have fairly small lattice parameters and at first glance might be a derivative of a cubic structure. Now consider what happens if your sample is in fact tetragonal. Since the lattice parameter a and c will differ, reflections like 100 and 001 will have different d-spacing and thus different 2Theta values ==>"split". Reflections like 111 and -111; 11-1; etc with all "1" permutated positive or negative will still have identical d-spacing, and thus have identical 2Theta values ==> "non-split".
In any good crystallography text book you will find all the equations for d-spacings in the different crystal systems and will be able to verify my arguments.
As peaks appear to be split into 2 peaks at most (?; verify at large 2Theta 120 to 150degrees) the sample does not appear to be orthorhombic or even lower metric symmetry.
As Marcella stated, more information is required for these types of questions: at least Instrument type, radiation, 2Theta range, collimation and detection system used; monochromator/analyser crystal yes/no; filtered radiation... ideally something about the sample, its preparation/ treatment history.
Incidentally, the data collection time was way too short! The last but one reflection is almost lost in the statistical noise. For a real, quantitative analysis you will need at least 5 to 10 times the exposure!
the 2theta range is 20-80 and the instrument used is rigaku miniflex diffractometer which is not strictly monochromatic as stated by Marcella. I think repeating the observation with more exposure time will give more insights.
Thank you
Others have mentioned longer counting time to smooth the data. That will often help, but there is another source of noise that looks present: poor particle statistics. Longer counting will not improve poor particle statistics. Notice for some peaks Kalpha2 is missing and in others Kalpha1 and Kalpha2 have the same intensity. This is from having a small number of crystallites in the x-ray beam. Grind the sample to get smaller particles or spin the sample during the scan or use a larger divergence slit (and cover a greater area of the sample holder with the sample.).
- Badges
- Science topic
- Similar topics
- Filing