Sintering behavior and thermal conductivity of Y2O3 fully stabilized HfO2 ceramics

A series of Y2O3 fully stabilized HfO2 ceramics (Hf1-xYxO2-0.5x, x = 0.20, 0.24, 0.28, 0.32, 0.36 and 0.40) were synthesized by solid-state reaction at 1500 degrees C. The phase composition, thermal conductivity and sintering behavior at 1400 degrees C of the ceramic bulks were studied. The Hf1-xYxO2-0.5x ceramics were comprised of pure cubic phase with disordered fluorite structure. No phase transformation occurred in the ceramics with Y3+ doping concentration ranging from 0.24 to 0.36. Both Hf0.64Y0.36O1.82 and Hf0.6Y0.4O1.8 samples revealed the lowest grain growth rate when sintered at 1400 degrees C, indicating good resistance to sintering. However, the Vicker's hardness and Young's modulus after annealed for 96 h at 1400 degrees C for the Hf0.64Y0.36O1.82 sample were 8.97 and 200 GPa, respectively, much lower than those of the Hf0.6Y0.4O1.8 (14.51 and 237 GPa, respectively). The thermal conductivity of Hf1-xYxO2-0.5x first decreased and then increased slowly as the Y3+ content increased, and the associated mechanism was discussed.

Automated summary

A series of Y2O3 fully stabilized HfO2 ceramics were synthesized and studied, showing that Hf0.6Y0.4O1.8 had higher hardness and Young's modulus compared to other compositions. The thermal conductivity of the ceramics exhibited a complex trend as the Y3+ content increased.