Dear Hosein, many thanks for posting this very interesting technical question on RG. One useful method to measure the oxygen content in bulk materials is chemical X-ray fluorescence analysis. For more information about this, please have a look at the following potentially useful articles:

A study of the composition and microstructure of aluminum matrix composites reinforced with alumina fibers

https://iopscience.iop.org/article/10.1088/1757-899X/124/1/012135/pdf

and

X-Ray Fluorescence Analysis for Oxygen on and in Materials

Article X-ray fluorescence analysis for oxygen on and in materials

The first article is freely accessible as public full text from the internet (please see attached pdf file).

Please also check the "Publications" section of RG for more information about this analytical method:

https://www.researchgate.net/search.Search.html?type=publication&query=X-ray%20fluorescence%20analysis

I hope this helps. Good luck with your work and best wishes!

Thank you dear Professor Frank, I am going to have a look on your suggested articles and try chemical x-ray fluorescence analysis. Best regards, Frank T. Edelmann