Phase transformation and nanocrystallite growth behavior of 2 mol% yttria-partially stabilized zirconia (2Y-PSZ) powders

Two mol% yttria-partially stabilized zirconia (2Y-PSZ) precursor powders were obtained through a co-precipitation process using ZrOCl2.8H2O and Y(NO3)3.6H2O as starting materials. Phase transformation and crystallite growth behavior have been investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). XRD results show that the crystal structure to be composed of coexisting tetragonal ZrO2 (t-ZrO2) and monoclinic ZrO2 (m-ZrO2) when the 2Y-PSZ freeze dried precursor powders was calcined at 773–1273 K for 2 h. The fraction of m-ZrO2 content is lower than 3.0 % when the calcination temperature is lower than 1073 K, whereas m-ZrO2 content rapidly increases to 8.7 % with the increase of calcination temperature to 1273 K. The crystallite size of t-ZrO2 increases from 12.3 to 30.2 nm when calcination temperature increased from 773 to 1273 K. In addition, the activation energy of t-ZrO2 and m-ZrO2 crytallite growth in 2Y-PSZ freeze dried precursor powders are 29.2 and 21.8 kJ/mol, respectively.