Crystal structure and electrical properties of gadolinia doped bismuth oxide nanoceramic powders

Abstract

A novel method of fabrication of gadolinia doped bismuth oxide nanoceramic via the sol–gel technique is reported. Their thermal, structural and morphological properties are described by measurements of Differential Thermal Analysis/Thermal Gravimetry, X-ray Powder Diffraction and Scanning Electron Microscopy. The samples have stable high ion conductive face centered cubic δ-phase nanocrystalline structure. The electrical measurements of the nanoceramic powders were carried out in the temperature range of (689–1091 K) using 4-point probe technique. There is a transition between two distinct regions at 720 °C, which can be attributed to the order–disorder transition. This observation is supported by the differential thermal analysis measurements. The experimental results show that the value of conductivity increases with increasing temperature over linear parts characterized by two different activation energies. The conductivity data over whole measured temperature range were fitted to the Arrhenius equations of conductivity and it shows two linear regions with different slopes which correspond to low-temperature range (689–975 K) and high-temperature range (999–1091 K). The values of Ea1 and Ea2 were obtained from the slopes of ln σDC versus q/kT plot as 1.25 eV and 2.81 eV for low-temperature range and high-temperature range, respectively.