Emergence of electronic conduction in bismuth oxide eletrolyte under high pressure

Abstract

The ionic transport properties of bismuth oxide (Bi2O3) were investigated under high pressures with impedance spectrum and Raman spectrum measurements. It was found that Bi2O3 is a pure ionic conductor below 9.0 GPa. Its pressure-dependent ionic conduction is determined by the diffusion rate of O2− ions. Above 9.0 GPa, the number of O2− ions that participate in electrical transportation are reduced rapidly by the pressure-induced distortion of crystal lattice, which becomes the essential factor to affect the ionic conduction. Most importantly, electronic conduction began to appear in the transportation process and coexist with the ionic conduction at 9.0 GPa indicating a few of originally localized electrons are involved in the electrical transportation due to the enhancement in distorted intension of Bi polyhedrons. Meanwhile, from the impedance spectra studies, it was also known that the electrical transport behaviors of Bi2O3 can be tuned by the frequency of input signals. At high frequencies, Bi2O3 behaves like an ionic solid electrolyte, but at low frequencies, it behaves like an electronic resistor.