I have prepared solid sol by taking 14 mol% Ytterbium in Titania. I know the Yb3+(0.860 Angstrom) radii is quite large compare to Ti4+(0.605 Angstrom). I did not observed any peak shift when I compared the XRD with undoped titania.
I general statement if doping occurs with larger radii with bigger ion than we observed peak shift in lower 2theta.
So, does It means no doping occurs?
My prepared titania is not highly crystalline material with composition of two pahse anatse and bronze.
I also observed seperate Yb2O3 XRD peaks which clears there is formation of seperate phase but when I refined the parameter of my volume of anatase and Bronze phase it shrinks.
Although Bronze phase is quite open structure with voids.
What could be reason for the lattice parameter to get reduce where is the possibilty of Yb can be in lattice so no such peak shift and lattice parameter varied without peak shift.
Dear Sanjeev Gupta
You don't say anything about the thermal treatment you applied to your sample. If it was heated just enough to form metastable, less dense phases then these may show more tolerance toward large ion size ratios and therefore to solid solution (doping). Note that if your structure has a lot of voids - created by water evaporation and incompletely collapsed by heating - then there will be room for larger ions without a large change in lattice parameters.
Also, was the thermal treatment under inert gas or vacuum? If so you'd expect to lose some oxygen, forming an oxygen-deficient Ti oxide phase with some Ti(3+) present. These "Magnelli" phases look quite similar to TiO2 in XRD. Some Yb(3+) may more easily find room in such a structure because Ti(3+) is larger than Ti(4+). But - if this reduction happens your sample should have turned blue or black, which you should easily see (or rule out) using your non-X-ray eyes.
However, there are other things that can happen in this system. In particular, Yb2O3 is a basic oxide, while TiO2 is an acidic one. You would expect them to react with each other and form stable (congruently melting) compounds. I didn't find a phase diagram for this system, but did for the Y2O3-TiO2, which must be very similar. Sure enough, there is a congruently melting compound, Y2Ti2O7. The phase diagram can be found in Article Phase equilibria of the TiO2–Y2O3 system
The analogous ytterbium compound, Yb2Ti2O7, is well known (CAS # 12037-03-5). If most of your Yb is in such a phase, you may miss it in XRD because (1) there isn't much of it and (2) you are not looking for its small peaks.
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