Structure stabilization by zirconia pinning effect of Y 2 Si 2 O 7 environmental barrier coatings synthesized by solution precursor plasma spraying process

Abstract

Abstract Y2Si2O7-xZrO2 coatings have been synthesized by solution precursor plasma spraying (SPPS) process. Their nanostructure is temperature-sensitive and is prone to sintering. This study explores the effect of zirconia introduction as a non-miscible secondary phase in the coating in order to take advantage of the Zener pinning effect and ensure a stabilization of the structure at high temperature. Short-time heat treatments and XRD analysis allowed to observe the yttrium silicate formation in the presence of zirconia. Then, after a 7-hour heat treatment at 1500 °C, the grain size distribution has been measured by image analysis on coating cross sections. The zirconia addition induced a stabilization effect of the grain boundary structure. Y2Si2O7 coatings are composed of grains with equivalent disc diameters (EDD) from 50 to 1500 nm. Y2Si2O7-0.25ZrO2 coatings have a bi-modal distribution with zirconia grains located at grain boundaries with mean EDD of 200 nm, and yttrium silicate grains with EDD between 500 and 1500 nm. Grains (with EDD > 500 nm) of Y2Si2O7-0.25ZrO2 coatings have a 10% higher circularity than those of Y2Si2O7 coatings resulting from Zener pinning effect.