Effect of applied pressure on microstructure and properties of hot-pressed Ca-doped LaCrO3 ceramics

High-density chromium deficient calcium-doped lanthanum chromite-based ceramics (La0.8Ca0.2Cr0.98O3) were prepared by hot pressing (HP) at different sintering pressures, and the highest density can reach 98.8%. The effects of sintering pressure on the microstructure, mechanical properties, and electrical conductivity of La0.8Ca0.2Cr0.98O3 materials were studied. The experimental results show that HP can increase the density of lanthanum chromite-based ceramic materials and significantly inhibit the growth of grain size. As the sintering pressure increases, the strength and hardness gradually increase, but the fracture toughness decreases. When the sintering pressure is greater than 58 MPa, the presence of the second phase CaCr2O4 can be detected in the XRD results of the sintered ceramics. The SEM results showed that CaCr2O4 had two completely different morphologies in the sintered ceramics, and it was initially speculated that the possible causes were due to two different generation pathways. The electrical conductivity decreases with increasing sintering pressure, whereas the maximum electrical conductivity obtained is 18.61 S/cm in vacuum at 800 degrees C for pressureless sintering ceramic.