In my case, one expects the shift to be at higher angle as the dopant site is lower than the host, but I see is that there is a part where it goes extreme right (for undoped) then shifts accordingly to higher angle as doping increases, but the shift is not so quite visible because in the undoped case, the major peak shift is very right as compared to the doping case. Say for example for undoped case it is at 33 degree but for the increasing doping, the major peak appears at 32.5 degree and keeps on increasing till 32.8 degree (but for the highest dopant, the major peak again decrease). And for the final doping case, the peak shifts to left side, such that not matching with other dopant variation. What reason should I give for this unusual behavior, if for a second, we don't think of the compounds we are dealing!!
Sorry for the reediting the question as the numbers (the angles basically) I mentioned in degrees was confusing and not consistent with the situation I described.
As for all questions regarding powder diffraction:
-include a graph of the diffraction pattern
-detail the diffractometer that was used (Bragg-Brentano Geometry, wave length, manufacturer, detector system, sample geometry etc.)
-specify a bit more on your sample system! At least, what is the crystal system, if you do not want to specify the composition. Is the observed effect systematic across the diffraction pattern, does it vary for different reflections?
-What dopant rate are you talking about ? A few per billion ? Or is this more of a nonstoichiometric compound with something of percentage ranges?
-Have you repeated the experiment with a new sample preparation as instrumental effects and errors can easily cause a peak shift in the range you are describing?
Any further comment would be pure speculation as you do not provide enough information to warrant a sound answer.
As Neder said, it would be helpful to see actual patterns. What is the base phase? What other reflections does it have?
Are you sure the samples are prepared properly? If there is variation in your sample height, the peaks will shift due to the changing geometry. If you prepare duplicates of the same sample, do the peaks appear in the sample place? I have seen data from past samples where the peaks bounced back and forth due to this reason.
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