Thermal Stability and Electrical Properties of High-Pressure-Molded Nanocomposites Containing Fast Ion-Conductive δ-Bi2O3 Phase

The report presents the electrical, structural, and microstructural properties of high-pressure–high-temperature-treated (HPHT) composites composed of δ-like Bi2O3 nanograins embedded in an aluminosilicate glassy matrix. Nanocomposites were obtained by heat treatment of the Bi2O3-Al2O3-SiO2 ternary glass system, followed by high-pressure molding (above 750 MPa). The total oxygen conductivity σt of the studied nanocomposites was high and approached a value of 4.5 × 10−4 S/cm at 600 °C. Due to HPHT treatment, we could also determine the intragrain conductivity of δ-Bi2O3 nanocrystallites. In this case, the value of σδ was even higher and was equal to 1.3 × 10−3 S/cm at 600 °C. It was also possible to study the temperature dependence of intragrain conductivity, showing two activation energies, which probably reflect the order–disorder transition within the sublattice of mobile O2− ions. The obtained nanocomposites exhibited promising properties for applications in electrochemical devices operating in the intermediate temperature range from 300 to 600 °C.