I have synthesized WO3 promoted vanadium phosphate, but I did not get any peak for WO3 in XRD. This may be due to the amorphous nature of WO3 or it was well dispersed or both. Could anyone make a suggestion?
Practically, you have a ternary system WO3-V2O5-P2O5. I have no good data exactly for this, but for MoO3-V2O5 a high solubility (ca. 20%) of MoO3 in V2O5(ss) is known (see "Phase Diagrams for Ceramists, #4467 & #5073). The the MoO3 cannot be found by X-ray, because it is not a separate phase. And typically WO3 is very similar to MoO3
Vanadium phosphate is not of that type catalyst. Please see my papers how it is synthesized. So there will be no possibility for solubilty. Anyway thank you very much for your remarks.
Do,t mind Dr Behera, Did you heated your sample during the process of synthesizing? If yes at what temperature?
One more thing i want to add in answer of Detlef Klimm that WO3 can be found by XRD. Please see http://www.sciencedirect.com/science/article/pii/S0927775709007286
I agree with Detlef (and I am happy to see I'm not the only one checking phase diagrams when dealing with more than one specie! plus, tungstates can be a nightmare). It should be noted that he does not say that WO3 cannot be found by XRD, but that in that particular case it is not possible to find it as a separate phase.
W is in any case quite a good scatterer so if you claim you have a good amount of WO3 in your system (either crystalline or amorphous) you must see a corresponding signal. Of course I assume your specimen is a powder (no preferred orientation, sufficiently small crystals, well prepared etc..). If WO3 is amorphous, then you should see the typical humps with one of the maxima compatible with the W-O distance. The equation is quite easy: no signal -> no separate WO3 phase (or too little quantity of material to give an appreciable effect).
If you are not convinced, a local chemical analysis (perhaps under the microscope) can help you solve the dilemma
Thank you very much Dr. Leoni for your reply. I agree with you. It might be difficult to get a separate phase for WO3 in XRD. What could you think about well dispersed? Can we say it for this purpose?
Mean you have promoted/ loaded the WO3 on vanadium phosphate , may i know how much weight % of WO3 you have put on the Vanadium phosphate?if your loading is less than 3 to 5% it is difficult to find the Peak due TO WO3 in XRD pattern......
Well dispersion of tungsten moieties on vanadium phosphate can be seen by the SEM and TEM studies
The material is of 5, 10, 15, 20 and 25 wt% WO3-VPO. Although its of higher wt% still i didn't get any peak. Yeah we can confirm well dispersion of material from the SEM and TEM analysis.
humnnn quite interesting !!! is there collapse of WO3 structure or incorporation into vanadium posphate ???
Gobinda, you better show here the set of diffraction patterns! It is highly unlikely that the specimen with the high percentage shows no difference with respect to the others. if WO3 is solubilised (Detlef's quite reasonable suggestion), you should see a shift in the peak positions of VPO. If not, you must see either some peaks or an increase in the "background" (telling you that it's not background but it's actually the WO3). I would have still expected to see confirmation of the chemical composition e.g. by EDXS
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