Effect of Y doping on microstructure and thermophysical properties of yttria stabilized hafnia ceramics

A series of Y2O3-doped HfO2 ceramics (Hf1-xYxO2-0.5x, x = 0, 0.04, 0.08, 0.12, 0.16 and 0.2) were synthesized by solid-state reaction at 1600 degrees C. The microstructure, thermophysical properties and phase stability were investigated. Hf1-xYxO2-0.5x ceramics were comprised of monoclinic (M) phase and cubic (C) phase when Y3+ ion concentration ranged from 0.04 to 0.16. The thermal conductivity of Hf1-xYxO2-0.5x ceramic decreased as Y3+ ion concentration increased and Hf0.8Y0.2O1.9 ceramic revealed the lowest thermal conductivity of similar to 1.8 W/m*K at 1200 degrees C. The average thermal expansion coefficient (TEC) of Hf1-xYxO2-0.5x between 200 degrees C and 1300 degrees C increased with the Y3+ ion concentration. Hf0.8Y0.2O1.9 yielded the highest TEC of similar to 10.4 x 10(-6) K-1 while keeping good phase stability between room temperature and 1600 degrees C.