Tuning the electrocaloric reversibility in ferroelectric copolymers by a blend approach

In electrocaloric active polymers, the ferroelectric copolymer P(VDF-TrFE) 65/35 mol% exhibits the largest caloric performance (ΔS = 190.0 J K^-1 kg^-1,ΔT = 45.4K at an electric field of 100 MV m^-1 and 85 °C) due to a sharp first-order phase transition. However, this high property occurs only at the first cycle and then drops significantly in the following electrical cycle, which significantly limits the promising applications of these copolymers. Here we use a blend approach to solve the irreversibility issue. We show that the incorporation of a terpolymer into a copolymer results in the evolution from normal ferroelectric to relaxor, which is accompanied by a large reduction in the thermal hysteresis. As a result, we find that complete reversibility of electrocaloric cycles in blends can be achieved for the copolymer/terpolymer volume ratio as 3/7.