Due to need of pollution-free and efficient-power-generation devices, in past few years, pace of research has been rapidly driven by fuel cell technology. The thesis contributes in the same regard, in which conventional solid electrolyte of solid oxide fuel cell is replaced by alternate material (Gd-doped-Ceria-GDC) and its performance has been tested. The process parameters of ceramic route and spray-pyrolysis-technique were optimized to obtain dense ‘electrolyte-grade’ GDC-bulk and thin-film samples, respectively. In symmetrical cell configuration, GDC-bulk sample showed open-circuit-voltage of 0.84 volts at 500°C. The grain interior conductivity of 13μm GDC-film deposited onto electrode-grade NiO-GDC substrate is ~0.1S/cm at 500°C.

In the present research, spray pyrolysis technique is employed to synthesize 10%Gd-doped ceria (GDC) thin films on ceramic substrates with an intention to use the "film/substrate" structure in solid oxide fuel cells. GDC films deposited on GDC substrate showed enhanced crystallite formation. In case of NiO–GDC composite substrate, the thickness of film was higher (~ 13 μm) as compared to the film thickness on GDC substrate (~ 2 μm). The relative density of the films deposited on both the substrates was of the order of 95%. The impedance measurements revealed that ionic conductivity of GDC/NiO–GDC structure was of the order of 0.10 S/cm at 500 °C, which is a desirable property for its prospective application.

In the present research work spray pyrolysis technique (SPT) is employed to synthesize GDC (10%Gd doped ceria) thin films on anode-grade-ceramic substrate (porous NiO-GDC). The film/substrate structure was characterized for their micro-structural and electrical properties along with their interfacial-quality. By optimization of preparative parameters of SPT and modification of surface of anode grade ceramic substrate, we were able to prepare the GDC films having thickness of the order of 13µm on NiO-GDC substrate. Further to improve the interfacial quality and densification of film, annealing of structure at 1000°C/8h were carried out. GDC films were fully dense (>96%), forming a gas-tight interface with substrate. Impedance measurements revealed that grain interior conductivity for GDC/NiO-GDC half-cell was of the order of 0.1S/cm at 500°C which is the desired conductivity for successful operation of SOFC. The activation energy for grain-interior and grain-boundary conduction estimated for GDC/NiO-GDC was 1.07eV and 0.93eV, respectively

In the proposed research, it was decided to synthesize the GDC and to demonstrate its use in IT-SOFCs. Initially, it was planned to synthesize the bulk GDC and study its different properties. For this, solid state reaction method was preferred due to its cost effective nature and ease of preparation procedure. The commercially available initial precursor materials were used to synthesize the GDC bulk. The process parameters of solid state reaction method were varied along with doping percentage of gadolinia in ceria to demonstrate its effect on structural, morphological and electrical properties of the prepared samples. This study was expected to provide intimate knowledge of processing parameters of solid state reaction method and its effect on the final product. It was also decided to vary Gd content in ceria to recognize the optimum level of doping for better solid-electrolyte properties. Attempts were made to synthesize samples with best results in electrical performance with an intention to use it in IT-SOFCs. Thin films of GDC for optimum concentration of Gd in ceria were prepared using Spray Pyrolysis Technique (SPT) due to its simplicity, cost effective nature and ease of preparation procedure. In this part of research, it was planned, initially, to prepare GDC films onto glass substrate to understand the film growth mechanism. A systematic variation in different preparative parameters of SPT was considered to prepare the electrolyte-quality films. Further these films were characterized at each step of optimization procedure by XRD, SEM, EDAX, AFM, and were analyzed for better understanding of SPT. Moreover, to demonstrate the solid-electrolyte-grade qualities of GDC films, it was also planned to study its interfacial properties with one of the SOFC electrodes. For this purpose, initially, ceramic anode material (NiO-GDC) as ceramic substrates (flat and thin) was prepared using solid state reaction method. These ceramic substrates were characterized and analyzed for the desired composition, porosity, flatness and thinness. Further, the good-quality GDC films were prepared on to ceramic substrates by the SPT to form electrolyte\electrode structure. The characterization of formed structure (electrode/electrolyte) was carried out during each step of optimization of SPT; using various techniques, such as, XRD, SEM, EDAX, AFM, impedance spectroscopy, etc. These characterizations helped us to narrow down the range of preparative parameters of SPT and post heat treatments. These optimizations were resulted in GDC films with desired properties and a good quality interface with the anode substrate. The formed interface was characterized using impedance spectroscopy. Finally, the samples were characterized for open circuit voltage (OCV) measurements to test its performance in typical fuel cell conditions.