Dear Dr. Hanggara Sudrajat ,
The doped of any metal on semiconductor leads to small red shift toward more 2 theta. This behavior will produce a less crystal size after doped metal on semiconductor, this process depends on the interaction between doped metal and the main metal in semiconductor, hence, if the doped metal has a less ionic radii compared with the ionic radii of the main metal in semiconductor, that will cause a good interaction and less crystal size ( i.e the size shifts to nano-size mostly.)
sincerely....
Dr. Luma
Doping in crystallite structures is well observed from XRD analysis via shift in peaks of diffraction angle if the dopants possess different radii in same coordination type than the metal to be substituted. In your case as there are two dopants so i suggest first to observe change via individually doping La and Cr in NaTaO3 as it would ease in understanding the observed effect of codoping.
Be careful with low range of 2theta. Remember that the accuracy (error) of 2theta - is strongly depends on the angle. Thus, observation of a shift at angles > 50-60 2theta is more accurate and right. Just compare, if any shift is found in parallel to low angle-distortion. Please, see the attachment.
Mrs. Luma M. Ahmed,
A "red shift" is a non-relevant term in XRD - it is about the spectroscopy.
Your assumption about dopant occupations prefaces from the simple supposition of solid solution (NaTaO3-LaCrO3) formation. This is possible, but not necessary. In the case of the formation of solid solutions, Vegard's law is implemented. However, it concerns only to ideal solid solutions. In fact, not the Vegard linear law itself is interesting, but nonlinear deviations from it… So, you need to make sure that solid solutions really do form (1). To do this, you need to make a series of compositions and look for the change of the parameters of the crystal lattice in this series.
In addition, from experience, it is known that small doping give a relatively large distortion in the lattice, and reasoning about ionic radii, as a rule, does not works.
- Badges
- Science topic
- Similar topics
- Chemistry