Study of valence states of copper in copper-phosphate glasses

Phosphate glasses containing CuO with composition, [(CuO)_x(P₂O₅)_1-x], x=0.10, 0.20, 0.25, 0.30, 0.40 and 0.50, were studied by magnetization, X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS). It was observed that compositional changes take place in going from batch to glass and these changes are more pronounced for low copper concentration. The ratio [Cu²⁺/Cu_total] as a function of x was determined from XPS and magnetization combined with RBS. The magnetization measurements suggest that more than 90% of the copper ions exist in the Cu²⁺ state in the glasses, while the XPS data show that less than 50% of the copper ions may be in the Cu²⁺ state. The low Cu²⁺ states detected by XPS may have resulted form reduction of copper ions upon exposure of the samples to X-ray radiation during measurement.