Properties evolution of plasma-sprayed La2Zr2O7 coating induced by pore structure evolution during thermal exposure

To study the inter-lamellar pores evolution under thermal exposure and how it affects the coating properties, free standing atmospheric plasma sprayed (APS) La2Zr2O7 (LZO) coating was subjected to thermal exposure at the temperatures of 1200 °C and 1300 °C for different durations. It was found that APS LZO coating experiences a rapid sintering during the early 5–20 h of thermal exposure. Such microstructure evolution behavior was attributed to the presence of the lamellar structure, which contains most 2D pores with a small inter-lamellar spacing. As a result, the density, inter-lamellar bonding ratio, mechanical properties and thermal conductivity of the LZO coating remarkably increase in about 20 h of thermal exposure. It was revealed that the evolution of the properties of the APS LZO coating during high temperature exposure is mainly ascribed to the shape change of the inter-lamellar pores for the formation of grain bridging in inter-lamellar pores.