Research On Low Temperature Sintering And Properties Of8YSZ Electrolyte Ceramic

In this paper, commercial8YSZ powder was employed as raw material,self-made SrO-TiO2water-cooled powders were used as additives, prepared8YSZelectrolyte ceramic by liquid phase sintering, Effects of various prepared factors onthe sintering, microstructure, phase compositions, mechanical properties andelectrical properties of8YSZ electrolyte ceramic were investigated based on thematerials analysis technology.SrO-TiO2water-cooled powders were prepared as following process: melted athigh temperature, quenched and then milled, and the influence of different meltingtemperatures on chemical components and phases were studied. The results showedthere were different small amount of impurities in all water-cooled powders besidesSrO and TiO2. Impurities were produced mainly because melted liquid dissolvedAl2O3and SiO2in crucible at1500~1600℃. Water-cooled powders were multiphasesystem, which contained both crystalline phases and amorphous phase, and therelative content of them changed by different melting temperatures. Crystallinephases were SrTiO3and rutile TiO2, Al2TiO5was observed in powder melted at1600℃. On this basis, Effects of heat treatment techniques on crystallizationdegree of water-cooled powders were further investigated and determined the mostoptimum crystallization process was holding1h at1300℃.SrO-TiO2water-cooled powders were employed as sintering additives andfurnace cooled to prepare corresponding8YSZ electrolyte ceramic. The resultsshowed the sintering mechanics for the ceramics turned to liquid phase sintering,which resulted in greater densification and larger grain size. The bending strengthand fracture toughness of8YSZ ceramic were improved by the densification. TheSrTiO3in the additives optimized electrical conductivity of grain boundary,densification improved the conductivity of ceramic, and however, the formation ofamorphous phases containing Si at grain boundary impaired the electricalconductivity. SrO-TiO2water-cooled powders were added to8YSZ and using certain heattreatment after sintering to prepare corresponding8YSZ electrolyte ceramic. Theresults showed that the heat treatment further promoted the densities of the ceramicand the growth of grain. Due to part of glass used to distribute at the grainboundary was turned into crystallization phase by the heat treatment, whichenhanced the structure of grain boundary and improved the bending strength ofceramic obviously. In addition, larger grain size and improvement of electricalconductivity of grain boundary were beneficial to improve electrical conductivityof8YSZ electrolyte ceramic.In conclusion, the sintering temperature of8YSZ electrolyte ceramic waslowered down and good mechanical and electrical conductive properties wereobtained with addition of self-made SrO-TiO2water-cooled powders by differentpreparation processes. Therefore, this research is valuable to related study on thepreparation of8YSZ electrolyte ceramics with excellent comprehensive properties.