IDENTIFICATION AND VIBRATIONAL PROPERTIES OF THE MIXED-OXIDE (1-X)V2O5 + XMOO3 (X-LESS-THAN-OR-EQUAL-TO-0.3)

The mixed oxide (1 - x)V2O5 + xMoO3 (x less-than-or-equal-to 0.3) has been synthesized by melting the oxides, and its structure and vibrational properties are investigated by x-ray diffractometry (XRD), x-ray photoelectron spectroscopy, Fourier transform infrared (IR) spectroscopy and Raman scattering. XRD revealed that the solid solutions of V2O5 with MoO3 are well formed except that the second phase V9Mo6O40 appeared at x greater-than-or-equal-to 0.1. It turned out that the unit-cell dimension c of the solid solutions (orthorhombic) initially decreases whereas a and b increase with increasing x, and that all the lattice parameters tend to remain unchanged above x congruent-to 0.1. The IR band due to the V-O stretching vibration at 1028 cm-1 shifted downwards, diffused and decreased in intensity with increasing x; similar changes are observed in the Raman spectra of the mixed oxide. It is shown that the V valence transition from V5+ to V4+ occurs as V is replaced by Mo. The V4+-to-V5+ ratios obtained by deconvoluting the V 2p3/2 line showed some qualitative agreement with the prediction for x < 0.1 based on no Mo valence transition and the V5+ --> V4+ transition as V is replaced by Mo. It is concluded that the V valence transition is responsible for the vibrational property changes of the mixed oxide with x.