Conduction models of semiconducting calcium borate glasses containing iron oxide

Abstract

The ac electrical resistivity, dielectric constant, and dielectric loss of the calcium borate glass system are investigated in order to determine the conduction models of the system. The glass series contains different iron concentrations in the system of molar composition (70−x)B2O3-30CaO-xFe2O3 with x up to 32%. The electronic properties are measured from 77 to 800 °K in the frequency range from 20 Hz to 100 kHz. The work has proved that the glasses are electronically conducting. The experimental results support the following models of conduction: (a) hopping conduction for glasses containing less than 20 mole% Fe2O3, (b) trap-limited band conduction together with hopping conduction for glasses having Fe2O3 mole% between 20 and 30, and (c) diffusive conduction together with hopping conduction for glasses containing more than 30 mole% Fe2O3.