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Abstract
Vinylidene fluoride and trifluoroethylene copolymers (P(VDF/TrFE)) are ferroelectric polymers. P(VDF/TrFE) are crystallized in a paraelectric phase under special conditions, P(VDF/TrFE) formed a highly double-oriented crystalline film with no noncrystalline areas or lamella crystals. This film does not have a single-crystal structure, but has far more single-crystal-like features than any other solid polymeric material. Accordingly, it has been reported as a “single-crystalline” film (SCF) by Ohigashi et al. [Appl. Phys. Lett., 66, 3281 (1996)]. We investigated the formation process of a SCF by measuring its double refractive index. Furthermore, we evaluated the relationship between the degree of polarization and the degree of Pockels effect of the SCFs, by measuring the Pockels effects and the D–E hysteresis simultaneously. The Pockels coefficients of the SCFs were in proportion to the degree of polarization. The maximum Pockels coefficient of the SCFs obtained was 2.82 pm/V, which is 7 times higher than that of conventional lamella films of ferroelectric polymers.