Pyroelectric Coefficient and Heat Capacity of a Ferroelectric Copolymer of Vinylidene Fluoride and Trifluoroethylene at Low Temperatures

The temperature dependence of the static pyroelectric coefficient p and dynamic pyroelectric response voltage V s of a highly crystallized ferroelectric copolymer of vinylidene fluoride (75 mol%) and trifluoroethylene (25 mol%) is measured in the temperature range of 10-300 K. The observed p and the heat capacity C p derived from p / V s both decrease with decreasing temperature, tending toward zero in the vicinity of 0 K. The temperature dependence of C p is fitted to the capacity contributed from three- and one-dimensional acoustical modes of vibrations with Debye temperatures of 52 K and 460 K, respectively, and contributed from main optical vibrations. It is found that the one-dimensional acoustical vibrations and optical vibrations with an average frequency of about 290 cm -1 dominantly contribute to the primary pyroelectric coefficient p 1 .