Investigations of defect structures for V4+ in CBPB glasses with distinct V2O5 contents

Abstract The defect structure, d-d transition and EPR parameters for V4+ in 10CaF2-(20-x)Bi2O3-60P2O5-10B2O3-xV2O5 (CBPB) glasses with distinct V2O5 contents x are theoretically investigated from the perturbation formulas for tetragonally compressed octahedral 3d1 clusters. Linearly decreasing cubic field parameter Dq or increasing g|| and g⊥ with x are suitably reproduced by linearly decreasing content function of Dq or decreasing and increasing content functions of covalence factor N and relative tetragonal compression ratio τ. The overall slightly increasing and decreasing average and anisotropy of hyperfine structure constants are illustrated as the cubic increasing content functions of core polarization constant κ and reduction factor H. These content dependences are ascribed to the modulations in local tetragonal compression, crystal-field strength and electron cloud distribution near V4+ with x. V2O5 as strong network modifier inducing depolymerization of phosphate long chains and Bi2O3 as network former and modifier exhibiting discontinuous changes with x may account for these modifications of the local structural properties.