Phase transitions and CTE of 10mol%Sc2O3-1mol%CeO2-ZrO2 ceramics sintered from two commercial powders produced by Praxair Surface Technologies, USA and DKKK, Japan are studied. Morphology of powders and grain structure of ceramics were studied by SEM and AFM. Ceramics produced from Praxair powder exist in cubic phase while DKKK-based ceramics exhibit slow phase transformation from cubic to rhombohedral (β) phase at temperatures 350–400°C. c-β Phase transition temperature is 440°C obtained by high temperature x-ray diffractometry (HTXRD) and differential scanning calorimetry. Coefficients of thermal expansion of cubic and β-phases were calculated from temperature dependence of lattice parameters obtained by HTXRD in the temperature range of 25–800°C. These results can be further used for the optimal design of SOFC layered structures as well as for determination of their reliability and durability under operational conditions.

The sintering behavior of two commercial powders with composition of 10 mol% Sc2O3-1 mol%CeO2-ZrO2 produced by Praxair Surface Technologies and DKKK is studied. DKKK powder has significantly higher sintering activity and requires a 200 degrees C lower sintering temperature than Praxair powder. It was shown that this difference in sintering activity of powders is a result of differences in powder morphology, chemical composition and the level of impurities. Powders have significant amount of the secondary rhombohedral phase (beta-phase) that reversibly transforms into cubic phase (c-phase) at temperatures above 500 degrees C. All samples of both powders sintered at temperatures higher than 1200 degrees C exist in cubic phase at room temperature. DKKK-based samples have c-beta and beta-c phase transitions at temperatures 340 and 450 degrees C while Praxair-based ceramics are fully stabilized in the temperature range RT-850 degrees C. Coefficients of thermal expansion were obtained from XRD data for c- and beta-phases the temperature range of 25-850 degrees C. The beta-Phase has a lower density and CTE than c-phase. Hardness and fracture toughness of ceramics sintered at different temperatures were studied by the microindentation method. Hardnesses of Praxair- and DKKK-based samples are 10.2 and 12.8 GPa respectively. Fracture toughness of all samples is in the range of 2-3.5 MPa.m(0.5). Stressed areas under the indents are subjected to relatively fast c-beta temperature-induced phase transitions. The results of this can be used in the optimal design of SOFC layered structures as well as the determination of their reliability and durability under operational conditions.