Understanding the thermal decomposition mechanism of La2Zr2O7 during isothermal exposure

Abstract

The objective of this work is to suggest the thermal decomposition mechanism at the subsurface of plasma-sprayed La2Zr2O7 (LZO) before and after isothermal exposure. The free-standing LZO coatings were prepared and suffered from volatile thermal decomposition on the subsurface during thermal exposure. The La2O3 was evaporated during thermal exposure from the subsurface because of its high vapor pressure, producing the de-mixed layer consisting of La-rich and La-deficient areas in the shape of an isolated island and a lamellar structure. Some of the pre-existed pyrochlore LZO phase was transformed to monoclinic ZrO2 because of the absence of the La2O3. The thermal decomposition behavior is discussed in detail, and the possible decomposition mechanism is suggested.