X-RAY-PHOTOELECTRON AND X-RAY-PHOTOABSORPTION STUDY OF PRESSURE-AMORPHIZED T-NB2O5

A recent report suggested that pressure-induced amorphization of the T phase of Nb2O5 is accompanied by a reduction of Nb from the pentavale nt state with the simultaneous loss of oxygen atoms. This conjecture i s examined in detail by x-ray-photoelectron and x-ray-absorption spect roscopy. No reduction was detected within the sensitivity of the measu rements, which impose an upper limit for the concentration of reduced Nb, if any, to be less than 3%. The L(II,III)-edge photoabsorption spe ctra suggest that the recovered high-pressure phase has a more compact ed oxygen environment, which is often found in densified materials.