Toughened ceramics in the system Al2O3:Cr2O3/ZrO2:HfO2

Abstract

Composites of Al2O3:Cr2O3 solid solution matrix with ZrO2:HfO2 solid solution dispersed particles were prepared and their properties studied. Thermal conductivity of compositions containing 20 mol% or more of chromia was found to be lower than that of partially stabilized zirconia at temperatures above 700[deg]C. Specimens in this system were annealed at 1000[deg]C for longer than 500 h and no mechanical property degradation was observed. Modulus of elasticity, bend strength and fracture toughness of these composites depend strongly on composition, volume fraction, size and the crystallographic modification of the dispersed particles. Best average bend strength of the composites is 490 MPa and the best average fracture toughness observed for these composites was 7[middle dot]4 MPa m1/2. It was found that the fracture toughness of some of the compositions increased with increasing temperature reaching a maximum of 300-500[deg]C, and returned to the room temperature value at 1000[deg]C. From the results obtained these composites can be considered as a potential candidate for advanced heat engine applications.