Electrical conductivity of Gd-doped ceria with nano-sized grain

Abstract

Ce 0.8 Gd 0.2 O 1.9 (Gd-doped ceria, GDC) powder synthesized by glycine-nitrate combustion process was densified to 96 % of theoretical density at 900 ºC for 5 min using spark plasma sintering (SPS) process. The grain size of the GDC sintered using the SPS process was about 20 nm. The electrical conductivity of GDC sintered using SPS process was obtained from the AC impedance measured at a frequency range of 42 Hz to 5 MHz, and was compared with that of GDC sintered at 1200 ºC for 4 h in air using normal sintering process with a grain size of 150 nm. The electrical conductivity of GDC sintered using SPS process was one order of magnitude lower than that of GDC sintered using normal sintering process. The contributions of the bulk and the grain boundary to the total electrical conductivity were distinguished by analyzing the AC impedance of the GDC sample. The conductivity of the bulk slightly decreased with decreasing the grain size, while the conductivity of grain boundary increased with decreasing the grain size.