Flexible and lead-free barium strontium titanate based generatrors

In this study BST thin films were RF sputtered on gold/polyethylene dioxithiophene coated polyethylene naphthalate flexible substrate and piezoelectric generator with top patterned electrodes was designed. The composition of the films, piezoelectric response of the device, dielectric losses, capacity and mechanical stability were investigated. It was found that device consisting of barium strontium titanate (BST) films with thickness of 420 nm and composition of Ba
0.5
Sr
0.5
TiO
3
, exhibited high capacity of 4.65 µF, low dielectric losses of 10
⁻³
- 10
⁻²
in a broad range of frequencies and produced average voltage of 80 mV at applied low frequency vibrations with intensity of 350 g. The average produced power was 7.02 µW per bending cycle and the power density was ~2.34 µW/cm
²
. Maximal longitudinal piezoelectric coefficient d
33
was found to be 10.8 pC/N The mechanical stability is satisfying, as the variation of the capacity was not greater than 17% up to 320 bending cycles, and the device resisted to 500 cycles without degradation. This might be due to the presence of elastic polymer at the bottom electrode interface. The results show superior performance of the generator, as compared to the available results.