Polarization distribution and process of depolarization in VDF/TrFE ferroelectric copolymers and its composites by means of laser intensity modulation method

Measuring system and method as well as data processing of the laser intensity modulation method(LIMM) have been set up. The polarization distribution and the process of depolarization for VDF/TrFE ferroelectric copolymers are investigated by LIMM. The pyroelectric coefficient shows a maximum at a distance of about 8 μm from the two surfaces of 25 μm-thick VDF (80)/TrFE (20) sample, while it shows a maximum at the centre for 12 μm-thick one. The polarization displays a symmetric pyroelectric distribution. Annealing at 145°C introduces depolarization. The pyroelectric coefficient decreases gradually from one side of the sample to the other with increasing annealing time and disappears at about 2 h later. The pyroelectric coefficient for 30 μm-thick VDF(70)/TrFE(30) film poled by dc electric field at room temperature tends towords a constant at 6 μm and 8 μm from the two surfaces of the sample respectively, and produces an antisymmetric pyroelectric distribution.