Enhanced thermal stability of SiAlCN thin film thermistor with PDC-SiAlCN coating for high-temperature applications

SiAlCN thin films have great potential for high-temperature sensor applications due to their favorable thermal stability. In this work, to improve the high-temperature stability of SiAlCN thin films, a PDC-SiAlCN protective film for SiAlCN sensitive films was developed. The PDC-SiAlCN coating with a thickness of approximately 12 μm was successfully deposited on sputtered SiAlCN sensitive films via screen printing. SiAlCN thin films without a protective layer and those with Al 2 O 3 protective films were also prepared for comparison. The experimental results show that the SiAlCN films with PDC-SiAlCN coatings remain structurally intact after high-temperature testing, while the samples with Al 2 O 3 protective films show cracks as the temperature rises to 800 °C. The SiAlCN film samples with PDC-SiAlCN coatings exhibit a low resistance drift rate of about 0.71 %/h at 900 °C for 10 h. The drift rate of these samples is lower than that of the uncoated samples across the entire temperature range during isothermal tests. The samples with PDC-SiAlCN coatings not only deliver superior high-temperature stability within 800 °C, but also extend the applicable temperature limit up to 900 °C. During cyclic temperature tests from 200 °C to 900 °C, temperature data acquired from the SiAlCN film thermistor agree well with readings obtained from a commercial K-type thermocouple. The results reveal a low average measurement error of only 0.9 %. In terms of response time, the thermistors with a PDC-SiAlCN coating also exhibit obviously faster responses compared with the commercial thermocouple. The SiAlCN film thermistors with PDC-SiAlCN coatings are expected to be promising candidates for high-temperature monitoring applications.