HELLO,
i would like to ask a help for finding proper peak for my XRD results.
What i believe is my product shows crytallinity of WO2.90, but i am pretty not sure that this really is.. i put the JCPDS card of WO2.90 Below my XRD results, am i right?
or else, is there somebody who can help to fit the peak of it?
I suggest to stop to do your diffraction analysis based only on ICCD/JCPDS cards. In my opinion (and experience) they only should be used as inspiration but not to do proper science. This looks like a diffraction pattern from a highly defective material. It is not unlikely that the diffraction pattern is all from the same material which shows pronouncedly anisotropic line broadening due to a very anisotropic defect structure with extended defects. There is a lot of literature about these tungsten oxides around, and like always it requires (generally) deep digging into the evidence contained in the literature and (especially here) understanding into the ways powder diffraction phenomena are generated from defective materials (beyond simple isotropic line broadening due to simple size or microstrain). Note that these database entries are the scientists' interpretations of their diffraction data, and even apparently quite distinct entries can correspond to quite similar materials.
If this pattern is due to some largely homogeneous (single phase) material, it seems that the periodicity is quite perfect in one direction (with a corresponding d spacing) and quite imperfect in the other direction, e.g. some layer faulted material. It may even be possible that it is not possible to distinguish between essentially different structure models in the literature based on such data.
hmm...there isnt clearly well correaponding features of material which i believe this is in references...maybe its containing some otherelse (mixed)
then how can i figure out the stohichiometry of this material?? i was trying to define the crstal structure from XRD and XPS analysis..
I have now gone through the ICSD database (unequal ICDD). The narrow reflections (which you already have identified as higher orders (010) and (020) based on some ICDD/PDF entry) most likely correspond to the W-W distance resulting from W-O-W bridge due to corner-sharing octahedra (d approximately 3.8 Å; assuming that your data were collected with Cu radiation). A significant number of WO3-x structures are variants of the ReO3 structure having a pseudocubic lattice parameter of this 3.8 A. According to a couple of structures of WO3-x I have looked at now, one of these directions is retained as translation vector and usually ends up as shortest lattice parameter in the structure descriptions. It can in principle end up as a, b or c, depending on the choice of axes. Perpendicular you then have more complicated connectivities, including edge sharing of octahedra and pentagonal bipyramids around W. However, the 3.8 A remains as some lattice parameter! The more complicated structure motifs occurring perpendicular to the 3.8 A direction are then more prone to growth errors. Hence you have the narrow e.g. (001) and (002) or (010) and (020) and the rest gets strongly broadened. This is your broad reflections! Your task is now to go through the different structures available in the literature, simulate the diffraction patterns and look at what is additional to what is in your case the narrow reflections. Perhaps you find also some kind of review of the structure systematics of WO3-x.
Note that there are likely different series of structures which can be relevant and they occur sometimes under somewhat arbitrary names/formulas. There is the concept of chemical shear/twinning (Hyde&Andersson?) by which you in principle can generated infinitely many structures of arbitrary composition. In that case apparently quite different crystal structures can yield quite similar diffraction patterns. Superspace can then be used to work out the similarity and to work out the evolution of the diffraction patterns. Since I mention the ICSD (unequal ICDD) database: Not all interesting structures are there. Again, databases are mainly for inspiration, and they are full of error (although sometimes the also expose errors in the original literature)!
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