Performance evaluation and correction of Al2O3 and YSZ-doped In2O3/In2O3 multilayer heterogeneous thin-film thermocouples up to 1850 ℃

Temperature is a crucial physical parameter that defines the state and properties of materials, playing an essential role in both production and daily life. Industries such as aerospace, steel metallurgy, and energy have a high demand for high-temperature measurement. In particular, aviation engines are critical to modern industry, and their reliable operation are essential for both economic stability and national defense. The new generation of engine combustion chamber operates at temperatures up to 1800 °C, presenting challenges that traditional high-temperature sensors are unable to meet. In recent years, researchers have successfully developed thin-film thermocouples (TFTCs) that can meet the aero-engine temperature measurement needs. Compared to traditional high-temperature sensors, TFTCs offer advantages such as compact size, rapid response, and high measurement accuracy. Moreover, their integration directly onto engine surfaces minimizes interference, enhancing the safety and efficiency of engine operation. The sensitive layer materials of TFTCs mainly include metal and semiconductor ceramic materials. The main reasons for the failure of TFTCs currently include thermal oxidation failure of sensitive materials, thermal stress mismatch caused by differences in thermal expansion coefficients of multi-layer heterogeneous thin films at high temperatures, resulting in film cracking, detachment, or delamination.

 The research on TFTCs focus on structural design and exploration of new sensitive materials, aiming to develop semiconductor thermoelectric material systems with higher Seebeck coefficients to surpass traditional metal K-type, R-type and S-type thermoelectric materials. The research has successfully achieved good thermoelectric performance under high temperature conditions and has higher sensitivity than traditional metal materials. However, the current upper limit of TFTCs falls short of the 1800 ℃ required by advanced engine designs, underscoring an urgent need to push the limits of TFTCs technology. Research into ultra-high temperature TFTCs is crucial for high-temperature sensor technology, optimizing the performance of aerospace engines and gas turbines, and ensuring operational efficiency and safety.

A team led by Professor Bian Tian from the Institute of Xi’an Jiaotong University, China, recently addresses these challenges by proposing a novel In₂O₃ yttria-stabilized zirconia (YSZ)/ In₂O₃ ultra-high temperature TFTC sensor. Previous research on YSZ has mainly focused on its mechanical and thermal insulation properties as a ceramic material, its application as a protective layer and thermal barrier coating, or the investigation of YSZ preparation methods. However, there has been no research on blending YSZ with thermoelectric materials to enhance their performance. This study designs TFTCs based on their temperature measurement principles, first principles and simulations. At the same time, using neural network technology to combine deep learning algorithms with experimental data of TFTCs. The experimental data are trained and learned to establish a nonlinear mapping between error signals and real signals, improving the repeatability accuracy of TFTCs. Finally, an In₂O₃ (YSZ)/ In₂O₃ ultra-high temperature TFTC based on neural network technology regulation is obtained, providing a practical and feasible solution for 1800 ℃ ultra-high temperature measurement.

The team published their work in Journal of Advanced Ceramics on May 29, 2025.

“In this report, we proposes an ultra-high temperature thin film thermocouple temperature sensor based on YSZ (yttria stabilized zirconia) material doping. The material properties are improved by doping an appropriate proportion of YSZ in In₂O₃. Based on the temperature measurement principle, first principles, and simulation of the thermocouple, this study designs the thermocouple and prepares it through screen printing technology to obtain a usable ultra-high temperature thin film thermocouple sensor with a maximum measurement temperature of 1850 ℃. Simultaneously utilizing neural network technology to improve the repeatability accuracy of thin film thermocouple testing, a neural network-based In₂O₃ (YSZ)/ In₂O₃ ultra-high temperature thin film thermocouple temperature sensor was ultimately obtained, providing a practical and feasible solution for ultra-high temperature measurement.” said Bian Tian, professor at School of Mechanical Engineering at Xi’an Jiaotong University (China), a senior expert whose research interests focus on ultra-high temperature and special piezoresistive MEMS sensors in aerospace and other fields.

“YSZ materials can maintain good structure and properties in high-temperature environments, and they are unlikely to undergo thermal decomposition or phase transformation. With a high melting point and excellent chemical stability, YSZ materials are resistant to corrosion from most acids, bases, and salts, making them an outstanding high-temperature doping material.” said Zhongkai Zhang, a member of Professor Bian Tian's team, a senior expert whose research interests focus on key technologies for high temperature sensing.

“To ensure the reliable operation of the prepared TFTCs at 1800 °C, tests were conducted at 1850 °C to provide a safety margin for use in an environment of 1800 °C. When the hot end temperature reached 1850 °C, the cold end temperature of the TFTCs was recorded at 262.3 °C. The maximum Seebeck coefficient was calculated to be 163.4 μV/°C.” said Bian Tian.

“In the vibration impact test with a vibration acceleration value of 21.17g and a maximum impact of 100g, the resistance and voltage of the In₂O₃ (YSZ)/ In₂O₃ thin film thermocouple were relatively stable before and after the test, and the output signal did not change due to vibration impact. In the application testing of air turbine rocket engines, it has been proven that the studied thin film thermocouple can operate in a high-temperature gas environment at an outlet temperature of 1090 ℃.” said Zhongkai Zhang.

“In the future, we will conduct long-term stability testing and high-temperature destructive experiments on sensors to further investigate their performance under different working hours and extreme conditions. This will involve analyzing material aging and sensor failure mechanisms, as well as proposing potential solutions.” said Zhongkai Zhang.

Other contributors include Jiaming Lei, Le li, Bo li, Zhaojun Liu from the School of Mechanical Engineering, Xi’an Jiaotong University, China;Yong Xia, Weixuan Jing from the School of Mechanical Engineering, Xi’an Jiaotong University, China; Dan Liu from the State Key Laboratory of Dynamic Measurement Technology, North University of China, China.

This work was supported in part by the National Key Research & Development (R&D) Program (No.2023YFB3209600) and National Natural Science Foundation of China (No.52475570).

About Author

Wang Meng, a doctoral student at the School of Mechanical Engineering, Xi'an Jiaotong University, is mainly engaged in research related to high-temperature temperature/strain sensors.

Zhang Zhongkai, associate researcher and master's supervisor at Xi'an Jiaotong University, member of the National Industrial Thermal Standards Committee, guest editor of CHEMOSENSOR and FRONTER MATRIALS journals, secretary of the Shaanxi Micro Mechanical Electronic Systems Research Center, mainly focuses on key technologies for high-temperature sensing. Published 17 first or corresponding author papers in internationally renowned journals such as Microsystems&Nanoengineering, International Ceramics, IEEE Sensor Journal, etc. As the project leader, led 5 national level projects including the Key R&D Program of the Ministry of Science and Technology, LYJJ Project of the Military Commission Science and Technology Commission, KSFC Project of the National Natural Science Foundation, and participated in 14 other projects such as the Two Machine Special Project. Authorized 17 national invention patents, 6 software copyrights, 2 US patents, 1 national standard, and 6 group standards; Applied for and received 23 national inventions and 4 national defense patents. Received 10 scientific research and competition awards, including the first prize of the Science and Technology Award from the Shaanxi Mechanical Engineering Society.

Tian Bian, Tian Bian (corresponding author), professor at Xi'an Jiaotong University and deputy director of the Institute of Precision Engineering at the School of Mechanical Engineering. Long term commitment to the research of ultra-high temperature and special piezoresistive MEMS sensors in aerospace and other fields, awarded the national talent plan. In the past 5 years, I have led or participated in 12 projects and published 120 academic papers, including 97 SCI indexed papers; Authorized 35 invention patents; Received 1 second prize for national technological invention and 1 first prize for science and technology in Shaanxi Province; The temperature/pressure/acceleration sensor developed has broken through the measurement difficulties under high temperature, high frequency response, extreme range and other conditions in aerospace, petrochemical, military, biological instruments and other fields. It has been applied to multiple aerospace units and solved technical problems such as ultra-high temperature temperature and pressure measurement.

About Journal of Advanced Ceramics

Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen. JAC’s 2023 IF is 18.6, ranking in Top 1 (1/31, Q1) among all journals in “Materials Science, Ceramics” category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508