A Comparative Study on the Phase Stability of ZrO۲-۸ wt. % Y۲O۳ : Nano- and Micro-Particles

At temperatures above ۱۲۰۰ °C, the phase instability of micro-YSZ : ZrO۲-۸ wt. % Y۲O۳ is one of the major causes of damage to Thermal Barrier Coatings (TBCs) of the latest generation of gas turbines. In this study, nano-YSZ was produced using a wet chemical method to improve the phase stability of micro-YSZ. The phase stability of both synthesized nano-YSZ and commercially available micro-YSZ was examined after ۵۰ h of heat treatment at ۱۳۰۰ °C. The data obtained from X-Ray Diffraction (XRD) analysis of nano-YSZ confirmed the formation of the non-transformable tetragonal (tetragonality parameter : < ۱.۰۱) phase of ZrO۲ and its improved stability followed by heat treatment. Micro-YSZ, however, was decomposed into two new phases, i.e., monoclinic and cubic ZrO۲ with the wight percentages of ۳۸ % and ۶۲ wt. %, respectively, under comparable conditions. The morphological features of nano-YSZ were assessed by Field Emission Scanning Electron Microscopy (FESEM), the results of which confirmed the formation of YSZ nanoparticles with an average size of ۴۰ nm. According to the findings, nano-YSZ could be a suitable candidate for use in TBCs of the next generations of gas turbines.

Keywords:

Thermal barrier coatings (TBCs) , YSZ : ZrO۲-۸ wt. % Y۲O۳ , Wet-chemical method , Phase stability