Understanding the thermal decomposition mechanism of La2Zr2O7 during isothermal exposure.

The objective of this work is to suggest the thermal decomposition mechanism at the subsurface of plasma-sprayed La 2 Zr 2 O 7 (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 La 2 O 3 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 ZrO 2 because of the absence of the La 2 O 3. The thermal decomposition behavior is discussed in detail, and the possible decomposition mechanism is suggested. • The thermal decomposition behavior of plasma-sprayed LZO was investigated. • The volatilization of La 2 O 3 transformed p -LZO to m -ZrO 2 and t -ZrO 2 during isothermal exposure. • The decomposed layer exhibits poor mechanical properties, resulting in the bad resistance from erosion and the impact of foreign objects. • A schematic diagram is suggested, illustrating the detailed decomposition mechanism at the LZO subsurface. [ABSTRACT FROM AUTHOR]