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

[Display omitted] • The HfO 2 /Al 2 O 3 multilayer heterogeneous thin-film insulation layer was designed and fabricated. • The multilayer heterogeneous insulation layer could increase the high-temperature electrical resistance from 7.39 × 104 Ω to 1.09 × 106 Ω at 1100 °C. • The equiaxed crystal HfO 2 grains could prevent the cracks detrimental to the electrical insulation from penetrating the insulation structure. • The Hf-O-Al amorphous layer with defects as electron and hole traps at the interface could inhibit the longitudinal migration of carriers. • The simulation analysis of the ITO-In 2 O 3 heat flux sensors with different insulation layers demonstrated that the multilayer heterogeneous insulation layer could meet the high-temperature application requirement of sensors with large sensitive layer resistance. 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 HfO 2 / Al 2 O 3 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 HfO 2 film could maintain the columnar grains of the TGO film by inhibiting the oxygen transport. Besides, the equiaxed crystal HfO 2 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 HfO 2 / Al 2 O 3 insulation layer was greatly improved. Furthermore, the simulation analysis of the ITO-In 2 O 3 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. [ABSTRACT FROM AUTHOR]