Non-elastic behavior of LaCoO3-based Ceramics

LaCoO3 and La0.8Ca0.2CoO3 ceramics show a non-elastic stress-strain behavior during 4-point bending experiments where hysteresis loops are observed during loading-unloading cycles. Permanent strain is stored in the material after unloading, and a mechanism related to ferroelastic domain switching in the rhombohedral perovskite is proposed. Domain switching in the materials was confirmed by X-ray diffraction. Fracture toughness of La0.8Ca0.2CoO3 measured by SENB and SEVNB methods coincide and are equal to 2.2 MPam1/2 at RT and decrease to around 1 MPam1/2 at temperatures above 300C. A decrease in fracture toughness is consistent with a ferroelastic behavior as the rhombohedral distortion decreases with increasing temperature.