Structural and magnetic properties of MoO3-TeO2 glasses

A series of tellurite glasses containing MoO3 With the nominal composition X(MoO3)-(1-x)(TeO2), where x = 0.10, 0.20, 0.30, and 0.40, have been investigated using X-ray photoelectron spectroscopy (XPS) and temperature-dependent magnetization techniques. The Te 3d core level spectra for all glass samples show symmetrical peaks at essentially the same binding energies as measured for TeO2 oxide and with full-widths at half-maximum (FWHM) that do not vary with increasing MoO3. These features indicate that the chemical environment of the Te atoms in the glasses does not vary significantly with the addition of MoO3 and that the Te ions exist in a single configuration, namely TeO4 trigonal bipyramid (tbp). The O 1s spectra, however, show asymmetry for samples with composition x <= 0.30 and are subsequently fitted with two peaks. One arises from the presence of oxygen atoms in the Te-O-Te, Mo-O-Mo and Te-O-Mo environments which are termed bridging oxygen (BO) and the other from oxygen atoms in an Mo = O environment which are termed non-bridging oxygen (NBO). The O 1s peak for x = 0.40 is more narrow and symmetric, and is fitted to a single peak due to the BO atoms. While the analysis of the Mo 3d spectra indicates the presence of Mo6+ ions only, the temperature-dependent magnetic susceptibility measurements shows a weak paramagnetic behavior which can be explained by having less than 1 at.% of the Mo ions existing in a magnetic Mo5+ valence state, a percentage below the detection level of the XPS determinations. (c) 2005 Elsevier B.V. All rights reserved.