Sammendrag
Mechanical characteristics of LaCoO%d based ceramics have been measured over the temperature range from room temperature (RT) to 850°C. The bending strength is in the range of 53 MPa for 83% dense LaCoO3, 76 MPa for 90% dense La0.8Sr0.2CoO3, and 150 MPa for 99% dense La0.8Ca0.2CoO3 ceramics at RT. The strength of LaCoO3 and La0.8Sr0.2CoO3 was relatively independent of temperature up to 850°C. The strength of the dense La0.8Ca0.2CoO3 material decreased linearly to 850°C, where the strength at 850°C is only about 50% of the strength at RT. The fracture mode of this material is changed from fully transgranular at RT to mixed trans- and intergranular at 850°C. Hardness in the range of 7-9 GPa for 90% dense La0.8Sr0.2CoO3 and 9-11 GPa for fully dense La0.8Ca0.2CoO3 ceramics have been observed. The fracture toughness is calculated to be 0.73±0.08 MPa.m1/2 for 90% dense La0.8Sr0.2CoO3, and 0.98±0.09 MPa.m1/2 for fully dense La0.8Ca0.2CoO3 ceramics. Young´s modulus for dense La0.8Ca0.2CoO3 was measured to be 112±3 GPa.
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