Phase transformation behavior of 3 mol% yttria partially-stabilized ZrO2 (3Y–PSZ) precursor powder by an isothermal method

The phase transformation behavior of freeze-dried 3 mol% yttria–partially-stabilized zirconia (3Y–PSZ) precursor powder has been studied. When the freeze-dried 3Y–PSZ precursor powder was calcined at 773–1073 K for 2 h, the crystalline structure was composed of tetragonal and monoclinic ZrO2 as primary and secondary phases, respectively. The freeze-dried 3Y–PSZ precursor powder after calcination at 773 K, the monoclinic ZrO2 content abruptly increased from 8.00% to 31.51% and the tetragonal ZrO2 content suddenly decreased from 92.00% to 68.49%, with the duration increasing from 0.5 to 1 min. The activation energy of the isothermal transformation from tetragonal to monoclinic was 7.02 kJ/mol. The kinetics equation for the phase transformation from tetragonal to monoclinic in the freeze-dried 3Y–PSZ precursor powder between 773 K and 1273 K for various durations is described as ln(1/1−α)=1/2.61[t2.61(1.50×10−3)2.61exp(−7.02×310/RT)]; whereas, the HRTEM image shows a typical monoclinic ZrO2 domain because of the stress-induced tetragonal to monoclinic ZrO2 martensitic transformation that has occurred.