Ionic Conductivity and Phase Transformation in Gd2 O 3 −  Stabilized Bi2 O 3

Abstract

Polycrystalline samples containing 14 mole percent (m/o) 86 m/o were fabricated by pressureless sintering powder compacts. As‐sintered samples were cubic . When annealed at temperatures below ∼755°C, the cubic phase transformed into a rhombohedral phase. Over the temperature range between 755 and 610°C, the equilibrium state corresponds to the two‐phase field containing the cubic and the rhombohedral phases. Below 610°C, the samples were single phase of rhombohedral structure. The samples were annealed for various periods of time and were characterized using x‐ray diffraction and optical microscopy. Conductivity of samples was measured by complex impedance spectroscopy, both as a function of time and temperature. Over the range of temperatures examined, the conductivity of equilibrium phase(s) exhibited four distinct Arrhenius plots. These were interpreted in terms of the conduction characteristics of the cubic phase, the rhombohedral phase, and mixtures of the two phases. The time dependence of conductivity was interpreted in terms of the cubic → rhombohedral phase transformation.