High-temperature property of flexible polyvinylidene fluoride/(Na_0.5K_0.5)NbO₃ vibration energy harvester

Abstract

Flexible polyvinylidene fluoride/(Na_0.5K_0.5)NbO₃ (PVDF/NKN) composite harvester was first characterized at high temperature. The origin of high flexibility is the unique structure assembled by alternately stacking four-sheets and three-fabrics (4-3 harvester). The 4-3 harvester was fabricated by uniformly dispersing piezoelectric NKN particles within a PVDF-sheet and a PVDF-fabric layer. Electric power-output of the 4-3 harvester was measured by using a custom-designed apparatus in the temperature range from 25 to 150°C and was compared with that of PVDF/BaTiO₃ (BT) harvester. The PVDF/NKN 4-3 harvesters and PVDF/BT 4-3 harvesters showed significantly different temperature dependences in the temperature range from 25 to 150°C. Electric power-output obtained at 25°C by applying an oscillation at 75 Hz in the thickness direction for the PVDF/NKN 4-3 harvesters and PVDF/BT 4-3 harvesters were 5.7 and 3.5 nW/cm² per an amplitude, respectively. In particular, at temperature above 130°C, the PVDF/NKN 4-3 harvester showed a stable output performance from 3.3 to 3.8 nW/cm², whereas the PVDF/BT 4-3 harvester demonstrated no electric power-output. Thus, the harvester composed of high T_C piezoelectric particles such as NKN is suitable as a vibration energy harvester operated under high-temperature environment.