X-ray diffraction is usefull instrument for detection type of  phases in mixture.

Oxides could be characterized by simple technique such as XRD and XRF (either EDS or WDS based). In case of XRF, your sample may give better result either in EDXRF or WDXRF.

For advance characterization one can go for X-ray Photoelectron spectroscopy technique too.

X- ray diffraction can be used to find out which of the above oxides are present provided the percentage of each oxide is sufficient to be characterized by this technique.

Hi Mahboubeh Alipour, X-Ray difraction, could be the most direct option, but also you could try using XPS

though the amount of the sample from the TGA analysis is low, it could be sufficient for an XRD measurement. This is the only sure method to determine which compounds are present in your sample, if all of them are crystalline (sio2 could also be present as amorphous phase..)

As all the other answers suggest, XRD is the best way to determine the oxides. Also, if you just need to know the elements, EDX from an SEM microscope can help you. I don't know about the university of Mashad, but Tehran university definitely has both in the Materials department as well as the electrical department. 

Thanks all of you for your informative suggestions. I was wondering if the TGA pruducts are in an amorphous phase, aren't they?!

Dear Mahboubeh Alipour,

The result of your assessment will depend much on sample preparation. as you are uncertain as to whether your reaction products are amorphous or crystalline, make sure to preserve any possibly crystallinity present by attributing least possible amorphization (or other artifacts) in sample preparation. Depending on the amount of material available, wet grinding under propanol in a micronizer  usually gives good results, alternatively in an agate mortar. For bulk assessment, XRD seems best suited, but you might want to check individual particles with SEM-EDS, possibly also EBSD on polished specimen to check crystallinity. You may want to spike your sample with a trace of known standard material (commonly ZnO, alpha-Al2O3, or Si-metal) for internal calibration, to allow quantification of phases.

Additionally, XPS/Auger can be used to verify specific bonding, but a bulk sample mixture (as opposed to purified material) may be challenging.

xrd is a good tool for phase identification 

There are also simple methods of qualitative analysis to distinguish between WO3 and (WO4)2- if these are not crystalline. Other than that like said before XRD is the method of choice.