Frequency-dependent ferroelectric heat cycles in polymer blends: Enhancements in electrocaloric performance of P(VDF-TrFE) and P(VDF-TrFE-CTFE)

Copolymer (P(VDF-TrFE-CTFE)) and terpolymer (P(VDF-TrFE)) have been widely investigated for their promising electrocaloric effect (ECE), whereas, their mixture of ECE has not been investigated. In this work, P(VDF-TrFE was mixed with a variety of concentrations of P(VDF-TrFE-CTFE) and its ECE effect was investigated in detail. Results indicated that after mixing of the copolymer, an additional change of adiabatic temperature (T + Tad) could be obtained. Moreover, the energy density (N_D) is drastically enhanced when the copolymer concentration increases up to 3 % due to antiferroelectric behavior of polymer blends (i.e. Copolymer content = 30 wt%). In addition, we observed that we can tune the working of frequency dependent ferroelectric heat cycle instead of pyroelectric heat cycle by changing the operational frequency in antiferroelectric range and the rejection of output heat is increased by decreasing the operational frequency (from 10⁻²Hz to 10² Hz). And we propose to use ΔT Vs E loop as the criteria to explain the ferroelectric heat cycle. Using this novel technique, we could successfully compare the efficiency of heat cycles. Three times higher efficiency of ΔT-E loop at low frequency (10⁻² Hz) was achieved due to the blend's antiferroelectric behavior.