Characterization of the pyroelectric coefficient of a high-temperature sensor

Temperature is one of the most important thermodynamic properties measured and controlled in energy generation systems. To operate the energy system at optimum operating conditions for lower emission and higher efficiency, it is important to measure real-time temperatures. Furthermore, temperature sensing in intense environments is necessary since most sensors in energy systems get exposed to elevated temperatures, corrosive environments, and elevated pressures. One of the solutions for developing harsh environment sensors is to use ceramic materials, especially functional ceramics such as pyroelectrics. Pyroelectric ceramics could be used to develop active sensors for both temperature and pressure due to their capabilities in coupling energy among mechanical, thermal, and electrical domains. In this study, Lithium niobate (LiNbO ₃ ) pyroelectric ceramic material was used to develop a temperature sensor for high-temperature applications. LiNbO ₃ has high Curie temperature (1210°C) compared to other pyroelectric ceramic materials. A high Curie temperature material is important since the polarization properties of the material break down above the Curie temperature. Hence, the use of a material with a higher Curie temperature, such as LiNbO ₃ , makes it promising to be used as a sensing material for high-temperature applications. A study was performed to actively measure the temperature up to 500°C using a pyroelectric ceramic lithium niobate (LiNbO ₃ ) as a sensor material. Due to the non-linear pyroelectric response of LiNbO ₃ , the temperature-dependent pyroelectric coefficient of LiNbO ₃ was measured with a dynamic pyroelectric coefficient technique in temperature ranges up to 500°C. Temperature-dependent pyroelectric coefficient of LiNbO ₃ was found to increase from −0.5 × 10 ⁻⁵ to −3.70 × 10 ⁻⁵ C/m ² °C from room temperature to 500°C. The LiNbO ₃ sensor was then tested for higher temperature sensing at 220°C, 280°C, 410°C, and 500°C and has shown 4.31%, 2.1%, 0.4%, and 0.6% deviation, respectively, compared with thermocouple measurements.