Effect of Bi 2O 3 proportion on physical, structural and electrical properties of zinc bismuth phosphate glasses

Abstract

The variation in physical, structural and electrical properties has been studied as a function of Bi 2O 3 content in 20ZnF 2–(10 + x) Bi 2O 3–(70- x) P 2O 5, 0 ≤ x ≤ 10 mol% glasses, which were prepared by melt quenching technique and characterized by differential thermal analysis (DTA). Colorless samples, which have no absorption peaks, are obtained for 10 and 12 mol% of Bi 2O 3 and the glasses are slowly becoming brownish from 15 to 20 mol% of Bi 2O 3 which exhibit two absorption peaks at ~ 370 nm, ~ 450 nm correspond to Bi° transitions 4S 3/2 → 2P 3/2 and 4S 3/2 → 2P 1/2 respectively. The decrease in 3P 1 → 1S 0 transition of Bi 3+ photo luminescence emission for 18 and 20 mol% of Bi 2O 3 and increase in optical absorption area shows the reduction of Bi 3+ to Bi°. From FTIR studies it is observed that an addition of Bi 2O 3 decreases the P―O―P covalent bond by forming P―O―Bi bonds due to high polarizing nature of Bi 3+ ions. Dielectric parameters like ε', tan δ and a.c. conductivity σ ac are found to increase and activation energy for a.c. conduction is found to decrease with the increase in the concentration of Bi 2O 3. Density of defect energy states is found to increase for higher concentration of Bi 2O 3 and is discussed according to quantum mechanical tunneling (QMT) model.