I have XRD data for WO3 thin film, which has a few number of peaks (2 ~4 peaks). Can I use FullProf to fit my data and obtain the refined lattice parameters and atom positions?
In principle, you can do it by Fullproof. However thin films usually show preferred orientation, they are strained due to synthesis. So you should consider touching these parameters during refinement. Again, the thickness of the film is crucial. It may cause peak-shifting. So consider instrumental errors (zero shift) at first.
In terms of sensitivity, Lab XRD provides fewer Bragg peaks, therefore, less information. To be satisfied, you can take a scan with Synchrotron-XRD or neutron powder diffraction.
Finally, yes, I think XRD data is sufficient if you only want to obtain the lattice parameters. Please be more careful while refining atomic positions.