Effect of sintering temperature on the transport properties of La2Ce2O7 ceramic materials

Abstract

La2Ce2O7 (LCO) based materials are of a paramount importance since they can be utilized for ammonium production, thermal barrier application, catalysts, hydrogen production and solid oxide fuel cells (SOFCs). In this work, a nano crystalline LCO powder was prepared using glycine-nitrate combustion method and then its properties were comprehensively characterized. The structural analysis of the synthesized LCO was carried out using conventional X-ray diffraction (XRD) and Raman spectroscopy. In a disordered phase, LCO is a biphasic mixture composed of C- and F-type phases. Densification studies were performed by sintering LCO pellets at different sintering temperatures. A densification of >= 95% was observed in all the samples with a very little variation. Sintering temperature had a marked effect on the electrical conductivity of LCO. The LCO sintered at 1100 degrees C showed the highest conductivity (3.68 mS/cm at 700 degrees C in air). The electrical conductivity was found to be decreasing with an increase in sintering temperature from 1100 to 1400 degrees C. To understand the behavior, the analysis of distribution function of relaxation times (DFRTs) utilized for correct separation of grain and grain boundary resistances. The presence of C- and F- type phases calculated from Raman spectra plays a crucial role in deciding conduction behavior of LCO. The results suggest a strong relationship between history of the ceramics preparation and their electrical properties.