Temperature dependence of elastic, dielectric, and piezoelectric properties of “single crystalline’’ films of vinylidene fluoride trifluoroethylene copolymer

• Published in: Journal of applied physics 1997-03, Vol.81 (6), p.2760-2769
• Main Authors: Omote, Kenji, Ohigashi, Hiroji, Koga, Keiko
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.364300

Elastic, dielectric, and piezoelectric constant matrix elements of a “single crystalline’’ (SC) film of vinylidene fluoride trifluoroethylene copolymer, P(VDF/TrFE), in which the orthorhombic [001] and [110] axes of fully extended chain crystals are preferentially oriented parallel to the stretching axis and normal to the surface, respectively, were measured at temperatures ranging from 10 K to the Curie point (402–404 K) by using a piezoelectric resonance method. All of the electromechanical coupling factors (k31, k32, k33, k24, and k15) are larger than those of conventional lamellar crystalline films. Some of the matrix elements for a P(VDF/TrFE) single crystal are derived from the measured values of constant matrix elements for the SC film. Some features characteristic of the SC film are revealed. The SC film has a large Young’s modulus for the stretching direction (1/s11) (121 GPa at 10 K). The properties related to the molecular motions along the chain axis, such as 1/s11, shear stiffness constant c55, shear piezoelectric constant e15, etc., exhibit strong relaxations around 250 K. The origin of these relaxations in the crystalline phase is discussed.