1981 Volume 89 Issue 1027 Pages 124-129
The effect of Ca-addition upon the vaporization of LaCrO3 has been studied in pO2 controlled atmosphere.
Powder samples having the composition, La1-xCaxCrO3 (x=0-0.15) were synthesized at 1400°C in air from the mixture of La2O3, Cr2O3 and CaCO3, and pressed to pellets and sintered at 1700°C. The pellet was suspended by Pt·20%Rh wire in an alumina tube of a Mo-wound hydrogen furnace and heat-treated at 1650°C in atmospheres of O2-Ar or H2-CO2 mixture (pO2=10-10-1atm) at flowing rate of 60cm3/min (NTP).
The weight loss of the specimen was almost proportional to heating time. The vaporization rates increased with increasing Ca content at any pO2, and showed a minimum value around pO2=10-2atm. The vaporization would be mainly attributed to CaCrO3 component from La1-xCaxCrO3 and the vaporization rate of CaCrO3 component would be fifty times as fast as that of LaCrO3 component.
The surface after vaporization was found to be composed of three phases of the initial perovskite (P0), another perovskite (P1) having a smaller lattice constant than P0, and monoclinic B-type La2O3 (B-L). The P1 phase was considered to be Ca-rich LaCrO3 formed by decomposition of CaCrO3 component.
