Doped materials should be checked first by XRD method. One must check whether the dopant atoms are statistically distributed the site of the atom you have replaced by doping. The best method to check that is neutron powder diffraction (NPD) but if you do not have that possibility then you must live with XRD. Once you successfuly refine the XRD or NPD data then you can make sure whether you have doped successfully. The formal doping concentration may not be correct but you can determine the true doping concentration by refining it. Once you make sure then you can also investigate the shuttle change of structure (crystal or magnetic). You can then perform whole lot of other characterization method. If your sample is magnetic hen you can measure magnetization. If your sample undergoes phase transitions then you can investigate them by heat capacity measurements. You can do all these if you have access to PPMS or MPMS instruments.

Dear Dr. Tapan Chatterji,

I would like to thank you for taking your valuable time to answer my question. I thought that XRD may be the first choice. However, how can be XRD be useful as the amount of dopant atoms is usually less than 5% molar ratio? How is it possible to detect the atoms in that low loading with XRD?

Sincerely yours,

Amin Hodaei

You must tell me first which material are you doping and with what dopant atom. It depends on the difference of the scattering powers of the atoms concerned. For XRD this often poses problems because two neighboring atoms in the periodic table are almost indistinguishable. In such cases neutron diffraction is very useful.

Dear Dr. Tapan Chatterji,

I was wondering how to substitute transition metal ions (Iron, Manganese, etc) with those of lanthanides. As usually they (lanthanides) are loaded into the host structures in low quantities. What is the ideal method in these cases?

Truly yours,

Amin

Dear Stefan,

as I wrote for Dr. Chatterji, the case thinking about is the incorporation of lanthanide(s) ions into the structures containing transition metal ions (like ferrites). In the cases that the guest ions have larger radii than that of host ones, the peaks regarding the substituted sites shift to lower diffraction degrees and vice versa. Can this phenomenon be always useful for determining the substitution completeness?

Considering the trivalent ions of lanthanide elements, the substitution with the transition metals ones (mostly possessing divalent and trivalent ions) both the aliovalent and isovalent dopings are faced. How are these different doping mechanisms in these cases distinguished and characterized?

Yours truly,

Amin 

Dear amin

We also faced the same problem when we tried to substitue bismuth in ferrite nearly we tried 8 times in all the cases we get slight shift less than half a degree in the lower diffraction side. Another samples normally we doped phases are formed for the as prepared samples but for Bismuth doped ferrite the phase is formed only after sintering the sample for 600 degree

Dear Prof. Gangatharan,

thank you for giving your valuable time answering my question. 

Yours truly,

Amin Hodaei