FABRICATION AND CHARACTERIZATION OF OXIDE HETEROSTRUCTURE

Abstract

Solid oxide fuel cells (SOFCs) convert chemical energy directly into electrical energy with relatively high efficiency and low emission of pollutants. However the operating temperature of SOFCs is required to be reduced in order to improve the durability and effectiveness of the cells. Performance of SOFCs could be enhanced at low temperature by fabrication of electrolyte and electrode materials in thin film form. In this thesis, I have investigated fabrication of Yttria Stabilized Zirconia material in bulk as wells as thin film form. The 8 mol% Yittria doped Zirconia (YSZ) powder has been synthesized using solid state reaction method and ball milling. First, both materials Yttria (Y2O3) and Zirconia (ZrO2) were mixed in appropriate amount using mortar and pestle. Further part of the mixed material was ball-milled for different time period. Finally ball-milled and conventionally mixed powders were sintered at different temperatures to prepare the desired cubic phase. Spark plasma sintering (SPS) was also used to prepare cubic phase of YSZ material. Parameters (Temperature, Pressure and holding time) of SPS were varied to obtain samples with higher density. X-ray diffraction (XRD) technique was used to conform the cubic phase of YSZ samples. The crystallite size of the YSZ powder samples was estimated from the XRD patterns using Debye Scherrer method. Dielectric properties of the samples prepared using solid state reaction mechanism and spark plasma sintering were measured as a function of temperature and frequency. Pulsed laser deposition was used to obtain thin films of YSZ on Si substrates. Structural and morphology of deposited thin films was examined using XRD and scanning electron microscope respectively.