Thermal properties and phase transformation of 2 mol% Y₂O ₃-PSZ nanopowders prepared by a co-precipitation process

Two mol% Y₂O₃-PSZ precursor powders for dental applications were synthesized using ZrOCl₂•8H₂O and Y(NO₃)₃•6H₂O by a co-precipitation process at pH 7 and 348 K for 2 h. The thermal properties and phase transformation of 2Y-PSZ nanocrystallite powder have been investigated using a thermogravimetric and difference scanning calorimeter (TG/DSC), Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy (TEM), selected area electron diffraction and dilatometric analysis. Two weaker broad exothermic peaks appear at around 618 and 718 K were explored in DSC results. The TG analysis shows that minor weight loss occurs from 298 to 348 K, followed by three major weight losses at 610, 630 and 773 K. Calcinated at 773 and 1273 K, the crystallized phases are composed of the major phase of tetragonal ZrO₂ and minor phase of monoclinic ZrO₂. TEM reveals that the tetragonal ZrO₂ with an average size of less than 20.0 nm is mainly aggregated into the secondary aggregates with a size of small than 30.0 nm. The sintering curve of the compact pellet has a significant shrinkage with a linear rate of 18.5% at about 1341 K. Maximum densification rate happened at 1473 K, demonstrating the good low temperature sinterability for dental applications.