Electrical insulation improvement from interface regulation for high-temperature thin-film sensors on superalloy substrate

Abstract

The stability and durability of insulation structure is crucial for the operation of thin-film sensors, especially at high temperature. However, it still faces great challenges in practical applications owing to the insulation failure during thermal cycles. In this study, an ALD Al2O3 film was introduced into the traditional TGO-sputtered Al2O3 insulation structure for interface regulation. After five thermal cycles up to 1000 °C, the modified insulation structure survived, while the control structure failed. The ALD Al2O3 layer could form denser equiaxed crystal during high-temperature crystallization, thereby preventing the propagation of cracks in sputtered Al2O3 due to volume shrinkage in phase transition. Furthermore, the ALD Al2O3 acted as a transition layer by forming semi-coherent interface with TGO Al2O3, stabilizing the multilayer insulation structure. Finally, Pt-PtRh thin-film thermocouples were fabricated on the modified insulation structure, which exhibited outstanding thermoelectric performance and stability at high temperature. Therefore, the interface regulation strategy proposed in this work could provide significant guidance for the development of high-temperature electrical insulation.