Theoretical studies of the concentration dependences of d-d transition band, g factors, and local distortion for V4+ in Li2 O-PbO-B2 O3 -P2 O5 glasses.

ABSTRACT

In this work, the g factors, d-d transition band, local distortion, and their concentration dependences for impurity V4+ in 20Li2 O-20PbO-45B2 O3 -(15 - x)P2 O5V2 O5 (0 ≤ x ≤ 2.5 mol%) glasses are theoretically investigated by using perturbation formulas of g factors for a tetragonally compressed octahedral 3d1 cluster. In the light of the cubic polynomial concentration functions for cubic field parameter Dq , covalency factor N, and relative tetragonal compression ratio ρ, the calculated concentration dependences of d-d transition band and g factors for V4+ show good agreement with the experimental data. With increasing x, N (≈0.7682-0.8165) displays the monotonously increasing trend, whereas ρ (≈6.5-4.2%) and Dq (≈1504.9-1481.1 cm-1 ) exhibit the decreasing tendencies. The above concentration dependences can be ascribed to the modifications of the V4+ -O2- bonding and orbital admixtures around the impurity V4+ due to the effects of V2 O5 doping on the stability of the glass network, the strength of local crystal fields, and the electron cloud distribution.