Sintering behavior of Ca- or Sr-doped LaCrO3 perovskites including second phase of AECrO4 (AE=Sr, Ca) in air

The sintering characteristics and mechanisms of stoichiometric alkaline earth metal (AE)-doped lanthanum chromites, including the second phase of AECrO4 with low-melting point in air, (La1−xAExCrO3, AE=Ca and Sr, 0≤x≤0.3), have been discussed. When x≤0.2, the sintering properties of La1−xCaxCrO3 are lower than those of La1−xSrxCrO3. However, the reverse results were observed at x=0.3. The mixtures of LaCrO3 and AECrO4 showed low sintering properties. It was found that the reaction of the second phases with LaCrO3 started at temperatures lower than the melting point. Thermal expansion coefficients (TECs) in the temperature range from 50 to 1000°C were 8.6×10−6/°C for LaCrO3, 13.1×10−6/°C for CaCrO4, and 17.5×10−6/°C for SrCrO4. The second phases with larger TEC among the LaCrO3 particles disturb the sintering characteristics of the LaCrO3 particles during the high temperature heat treatment.