Mechanical and thermal properties of combustion-synthesized perovskites, La1-xSrxCr0.2Fe0.8O3

This paper examined the room-temperature thermal and mechanical properties of a mixed conducting perovskite La1-xSrxCr0.2Fe0.80O3 (x = 0.2 to 0.8). Powders were made by the combustion-synthesis technique and sintered at 1250 degreesC in air. Sintered density, crystal phase, and grain size were characterized. Linear thermal expansion in air was also tested. Young's and shear moduli, microhardness, indentation fracture toughness, and biaxial flexure strength were determined. It was found that the linear coefficient of thermal expansion increased with increasing Sr content, while elastic modulus appeared to decrease with increasing Sr content. Young's modulus of 128 to 192 GPa and shear modulus of 51 to 74 GPa were measured. A biaxial flexure strength of 243 MPa was measured for the lowest Sr content batches. Batches with higher Sr concentrations (x = 0.6 to 0.8) showed extensive cracking. Indentation toughness showed a decrease with increasing Sr content. In addition, fractography was used to characterize the critical flaw and the fracture mode.