SYNTHESIS AND CHARACTERIZATION OF SOLID ELECTROLYTES BASED ON CeO2 FOR INTERMEDIATE TEMPERATURE FUEL CELLS

Four compositions in the range of 85-90 % CeO2, the other being SrO, CaO or Y2O3 combined two or three were studied. The mixtures have been homogenized by a wet route for 10 hours. After drying the obtained powders were subjected to thermal analysis which showed that in the process of grinding chemical changes occur. The apparent and relative densities were measured on the samples sintered at temperatures of 1350 and 1400 degrees C resulting that the relative densities of the samples are between 79 and 92%. X-ray diffraction revealed that the main mineralogical compound of the samples, thermally treated in the range of 1300-1400 degrees C, is a solid solution with a structure of fluorite type specific to CeO2. For some samples were also identified CaY4O7 and SrCeO3, compounds resulting by solid-phase reactions and two solid solutions of the type SrCe0,85Y0,15O2,95 and (Ce,Y)(2)O-3. The microstructure of the studied samples was investigated by electron microscopy and the results showed that the samples exhibit rounded and needle-shaped grains of different sizes. Electrical measurements have shown that three of samples have a corresponding behavior to solid electrolytes usable for IT-SOFC cells.