Pyroelectric thermometer for use at low temperatures

The applicability of pyroelectric thermometry to temperature change or temperature rate measurement at low temperatures was studied, with particular emphasis on calorimetry. The pyroelectric coefficients, dc dielectric constants, and volume resistivities of three ferroelectric ceramic materials, Clevite Ceramic B, PZT-4, and PZT-5A, were measured over the temperature range 4.2 to 300K. The pyroelectric coefficients were found to be reproducible, but large electric fields, thermal shock, and aging affected them. Expressions are derived for the temperature responsivity (voltage output per unit temperature change), noise equivalent temperature change (temperature change equivalent to the electrical noise in a pyroelectric thermometer), and figure of merit (a parameter characterizing the physical properties of a pyroelectric material). Typical temperature responsivities of 8.0 and 165 V/K, and values of noise equivalent temperature change of 2.5 and 0.12 μK, at 5 and 300K, respectively, are calculated. Recommendations are given for the use of a pyroelectric thermometer in a low temperature calorimeter.