Using in-situ synchrotron x-ray diffraction to investigate phase transformation and lattice relaxation of a three-way piezo-phototronic soft material

Abstract

A poly(vinylidene fluoride-co-trifluoro-ethylene) piezoelectric polymer is blended with nano particles of titanium oxide phthalocyanine to bridge photoconductive and piezoelectric effects. In this study, a system is examined by in situ synchrotron x-ray to test a three-way piezo-phototronic soft-material design. The sample is heated for in situ phase transformation characterization. The semi-crystalline poly (vinylidene fluoride-co-trifluoro-ethylene) polymer gradually transforms to an amorphous structure. A complementary piezoelectric experiment before and after the heating experiment shows that the piezoelectric performance is proportional to the phase ratio. Secondly, the system is examined to test its phototronic effect. Piezoelectric responses are measured by controlling the light illumination. The positive and negative controls of light illumination which validate this newly-designed system can be modulated by a three-way piezo-phototronic effect. In-situ synchrotron x-ray diffraction experiments are employed to measure the microstructure evolution as a function of applied voltage up to 800 V. We then turned off both the light and the applied voltage to examine the kinetic behavior of the system. There is orientation-dependent anisotropic relaxation. We compared the lattice-strain evolutions. Piezo-phototronic creep is found in the (110), but not the (310) planes.