Temperature measurements using a lithium niobate (LiNbO3) pyroelectric ceramic

Abstract

Temperature measurements from a power generation system could improve its overall safety and efficiency. In addition, real time temperature measurement could lead to a qualitative assessment of the health of the energy system. The challenge of real time temperature measurement inside of a power generation unit lies in the sustainability and the reliability of sensing materials in high temperature and corrosive environments. In this paper, a pyroelectric ceramic material (lithium niobate, LiNbO3) capable of sustaining high temperatures, is considered as the temperature sensing material. LiNbO3 is a pyroelectric material that generates current proportional to the rate of temperature change with time. This property is sustained by LiNbO3 until it reaches its Curie temperature (1210°C). The generated current could be used for many applications including temperature sensing and energy harvesting from waste heat recovery. This paper presents the temperature measurement results using a LiNbO3 pyroelectric ceramic. Ceramics with dimensions of 1cm×1cm with two different thicknesses, 2mm and 1mm, were used as the temperature measurement sensors. Two samples were heated by a 14.5W/cm2 heat flux and cooled with natural convection. Electrodes were made on both surfaces of the samples with high purity silver paint and two electrical leads were connected to a picoammeter to measure the generated current with respect to the rate of temperature change of the material during heating and natural cooling. A K-type surface thermocouple was attached on top of LiNbO3 to compare the temperature measurements and maximum 8% and 6.7% differences were found for 2mm and 1mm thick samples, respectively.