High Heat Insulating Thermal Barrier Coating Designed with Large Two-Dimensional Inter-lamellar Pores

Atmospheric plasma-sprayed ceramic coatings with a lamellar structure exhibit low thermal conductivity. However, high-temperature exposure causes sintering, which heals inter-lamellar two-dimensional (2D) pores and intra-splat pores. Such sintering effect increases the thermal conductivity of the coatings and consequently reduces the thermal insulation ability of TBCs. In this study, inter-lamellar 2D pores with a large opening width were introduced into the La₂Zr₂O₇ (LZO) coating through the spraying of a LZO-SrO coating and the removal of the SrO splats in water. Then, the conventional LZO coating and the porous LZO coating were subjected to high-temperature exposure at 1300 °C, for different durations. It was found that the 2D pores resulting from SrO splats present little healing during high-temperature exposure, while the conventional 2D inter-lamellar pores with a small opening width heal rapidly. Thus, the thermal conductivity of the conventional LZO coating increased rapidly, while the unhealed 2D pores in the highly porous LZO coating contributed to the coating low thermal conductivity. The present results indicated that a high heat insulating thermal barrier coating with high stability can be fabricated though the introduction of inter-lamellar 2D pores with large opening width.