Low-temperature specific heat measurement of a ferroelectric copolymer film of vinylidene fluoride and trifluoroethylene

The specific heat of a highly crystallized ferroelectric copolymer film of vinylidene fluoride (∼80mol%) and trifluoroethylene (∼20mol%) was measured over the previously unexplored temperature range from 3.7 to 8.5 K. The data show a dominant cubic temperature dependence, with only marginal evidence for a T^3/2 or a T² component. There is also no evidence for the discontinuity in slope that was observed in previous measurements of the pyroelectric coefficient of this material in the vicinity of 6 K. This difference is consistent with the supposition that thermal expansion is the dominant contributor to the pyroelectric coefficient in this temperature range. The specific heat data also show a rapid transition from the three-dimensional to one-dimensional Debye limits.