Strain Engineering for the Kapitza Resistance of the ZrO2/α-Al2O3 and YSZ/α-Al2O3 Interfaces

The Kapitza resistance is of fundamental importance for the thermal stability of the interface between the ceramic top coat and the thermal growth oxide layer in the thermal barrier coating structure, which is widely used to protect high-temperature components in current gas turbine engines. The top coat typically consists of the ZrO2 partially stabilized by 8% Y2O3 (YSZ), and the main component of the thermal growth oxide is alpha-Al2O3. In this work, the Kapitza resistance is found to be a small value of 0.69 m(2).K/GW for the YSZ/alpha-Al2O3 interface based on the heat dissipation simulation method. It indicates that the localization of thermal energy is rather weak, which is beneficial for the thermal stability of the YSZ/alpha-Al2O3 interface. This Kapitza resistance can be further reduced to 0.50 m(2) . K/GW by a mechanical or thermal compressive strain of 8%. To explore the underlying mechanism for this strain effect, we analyze the phonon vibration and the microscopic deformation in the interface region. It is revealed that the interface becomes denser through the compression-induced twisting of some Al-OZr and Al-OAl chemical bonds in the interface region, which is responsible for the reduction in the Kapitza resistance. The temperature effect and crystal size effect on the Kapitza resistance of the YSZ/alpha-Al2O3 interface are also systematically studied. These findings shall provide valuable information for further understanding of the thermal conductivity and thermal stability of the thermal barrier coating structures.