Zirconia-magnesia solid electrolytes processed by the citrate technique

ZrO2: x mol % MgO (X= 7,5, 9,7 e 11,9) ceramic solid electrolytes have been prepared by powder compaction and sintering at 1600 deg C. Magnesia-doped zirconia powders have been obtained by the citrate technique from hydrated zirconium oxide, magnesium nitrate, citric acid and ethylene glycol. Thermal analyses have been used to characterize the resins. Powder analyses comprise: particle size distribution, X-ray diffractometry and scanning electron microscopy. Solid electrolytes have been characterized by X-ray diffractometry, hydrostatic density, thermal neutron activation, scanning electron microscopy and impedance spectroscopy in the 5 Hz to 13 MHz and 300 to 800 deg C frequency and temperature ranges, respectively. TGA and DTA results show a strong exothermic processes during the resin decomposition followed by high mass loss. Simultaneously with the precursor decomposition, the development of crystalline phases are observed. Calcined powder consist of agglomerates with average sizes between 1 and 4 μm. Solid electrolytes prepared with these powders reached densities near 100% the theoretical value and electrical resistivity lower than that of commercial ceramic material. Thermal shock test carried out in these specimens show that the sintered material has a suitable u-and down-thermal shock resistance. The final conclusion is that zirconia-magnesia solid electrolytes can be prepared by the citrate technique to be used as transducers in oxygen sensors. (author)