Sintering behavior and thermal conductivity of Y 2 O 3 fully stabilized HfO 2 ceramics

A series of Y 2 O 3 fully stabilized HfO 2 ceramics (Hf 1 −x Y x O 2 − 0.5 x , x = 0.20, 0.24, 0.28, 0.32, 0.36 and 0.40) were synthesized by solid-state reaction at 1500 °C. The phase composition, thermal conductivity and sintering behavior at 1400 °C of the ceramic bulks were studied. The Hf 1 −x Y x O 2 − 0.5 x ceramics were comprised of pure cubic phase with disordered fluorite structure. No phase transformation occurred in the ceramics with Y 3+ doping concentration ranging from 0.24 to 0.36. Both Hf 0.64 Y 0.36 O 1.82 and Hf 0.6 Y 0.4 O 1.8 samples revealed the lowest grain growth rate when sintered at 1400 °C, indicating good resistance to sintering. However, the Vicker’s hardness and Young’s modulus after annealed for 96 h at 1400 °C for the Hf 0.64 Y 0.36 O 1.82 sample were 8.97 and 200 GPa, respectively, much lower than those of the Hf 0.6 Y 0.4 O 1.8 (14.51 and 237 GPa, respectively). The thermal conductivity of Hf 1 −x Y x O 2 − 0.5 x first decreased and then increased slowly as the Y 3+ content increased, and the associated mechanism was discussed.