Low-temperature measurements of the specific heat capacity of a thick ferroelectric copolymer film of vinylidene fluoride and trifluoroethylene

Abstract

The specific heat capacity c p of a 110 m thick and partially crystallized ͑ϳ77% ͒ ferroelectric copolymer film of vinylidene fluoride ͑PVDF͒ ͑ϳ75 mol % ͒ and trifluoroethylene ͑ϳ25 mol % ͒ was measured from 2 to 20 K. The temperature dependence of c p / T 3 reveals a shallow hump, centered at ϳ5 K, consistent with non-Debye behavior of semicrystalline materials. These c p data were used, in conjunction with previous measurements of the pyroelectric coefficient ͉pЈ͉, to infer the temperature profile of the macroscopic Grüneisen parameter based on ratios of ͉pЈ͉ / c p . Comparisons with similar data for PVDF are consistent with a correlation between anharmonicity of the interaction potential and excess specific heat capacity.