Multilayer heterogeneous electrical insulation structure of HfO2/Al2O3 for high-temperature thin-film sensor on superalloy substrate

Abstract

The real-time monitoring of the equipment operating in harsh environment is important for the cooling design and reliability analysis. However, the insulation layer of the thin-film sensors still faces challenges at high temperature, especially for sensors with large sensitive layer resistance. In this study, the HfO2/Al2O3 multilayer heterogeneous thin-film insulation layer was designed and fabricated. The minimum resistance of the control structure was 7.39 × 104 Ω at 1100 °C during multiple thermal cycles. However, the minimum resistance of the modified insulation layer was 1.09 × 106 Ω, exhibiting significant electrical insulation improvement. The HfO2 film could maintain the columnar grains of the TGO film by inhibiting the oxygen transport. Besides, the equiaxed crystal HfO2 grains could prevent the cracks detrimental to the electrical insulation from penetrating the insulation structure. Meanwhile, the Hf-O-Al amorphous layer with defects as electron and hole traps at the interface could inhibit the longitudinal migration of carriers. As a result, the high-temperature insulation performance of the HfO2/Al2O3 insulation layer was greatly improved. Furthermore, the simulation analysis of the ITO-In2O3 heat flux sensors with different insulation layers demonstrated that the multilayer heterogeneous insulation layer could meet the high-temperature application requirement of sensors with the large sensitive layer resistance.