Formation, Characterization, and Hot Isostatic Pressing of Cr2O3‐Doped ZrO2 (0,3 mol% Y2O3) Prepared by Hydrazine Method

Abstract

In the ZrO2‐Cr2O3 system, metastable t‐ZrO2 solid solutions containing up to 11 mol% Cr2O3 crystallize at low temperatures from amorphous materials prepared by the hydrazine method. The lattice parameter c decreases linearly from 0.5149 to 0.5077 nm with increased Cr2O3 content, whereas the lattice parameter a is a constant value (a= 0.5077 nm) regardless of the starting composition. At higher temperatures, transformation (decomposition) of the solid solutions proceeds in the following way: t(ss)→t(ss) +m+ Cr2O3→m+ Cr2O3. Above 11 mol% Cr2O3 addition, c‐ZrO2 phases are formed in the presence of Cr2O3. The t‐ZrO2 solid solution powders have been characterized for particle size, shape, and surface area. They consist of very fine particles (15–30 nm) showing thin platelike morphology. Dense ZrO2(3Y)‐Cr2O3 composite ceramics (∼99.7% of theoretical) with an average grain size of 0.3 μm have been fabricated by hot isostatic pressing for 2 h at 1400°C and 196 MPa. Their fracture toughness increases with increased Cr2O3 content. The highest KIc value of 9.5 MPa·;m1/2 is achieved in the composite ceramics containing 10 mol% Cr2O3.