Effect of calcining temperature on the tetragonal-to-monoclinic phase transition characteristics in 2 mol% yittria-doped zirconia ceramics

摘要

Two types of tetragonal-to-monoclinic (t-m) phase transition characteristics were observed in the 2Y-TZP powder samples. In the sample calcined below 1200℃, the t-m phase transition occurred below 200℃, and the fraction of the monoclinic phase increased sigmoidally. At the beginning of the transition, the fraction of the monoclinic phase increased gradually, and the lattice strain remained unchanged. The abrupt increase in the monoclinic phase accompanying the increase in the lattice strain of the tetragonal phase followed this. Finally, the fraction of the monoclinic phase was saturated, and the lattice strain dropped to 0%. The reaction between the adsorbed water and 2Y-TZP was essential for the t-m phase transition of 2Y-TZP to occur in air at around room temperature. The lattice strain stored in the tetragonal lattice assisted the phase transition. On the other hand, the fraction of the monoclinic phase increased, accompanied by a decrease in the lattice strain in the 1400℃ calcined powder. After the fraction of the monoclinic phase was almost saturated, the lattice strain dropped to 0%. A gas-solid reaction between the water vapor in air and 2Y-TZP and the diffusion of OH~(-) ion into the 2Y-TZP lattice were essential for this type of t-m phase transition.