MO5-GLASSES( IONS AS EPR STRUCTURAL PROBES IN MOLYBDENUM PHOSPHATE)

Glasses of P2O5-Li2MoO4-Li2O system with constant Li2MoO4 molar conten ts (10%), containing different amounts of the alkaline oxide (Li2O) ra nging from 0 to 30 mol%, have been studied by electron paramagnetic re sonance (EPR) spectroscopy. It is found that less than 1% of molybdenu m ions are reduced to Mo5+, this percentage decreasing with the Li2O c ontent. The components of g- and A-tensors are determined by computer simulations and related to structural properties using molecular orbit al method. The distorted octahedral environment of Mo5+ sites is confi rmed and minimal Mo-Mo distance is evaluated from the EPR linewidth as similar to 0.38 nm. At Li2O contents greater than or equal to 20 mol% , the coordination polyhedra of Mo5+ become better ordered though more distorted. The Mo-O bond covalency increases with increasing Li2O con tent. (C) 1998 Elsevier Science B.V.