Spatially-Resolved In-Situ/Operando Structural Study of Screen-Printed BaTiO3/P(VDF-TrFE) Flexible Piezoelectric Device

The incorporation of lead-free BaTiO 3 particles into P(VDF-TrFE) provides a versatile way for tuning dielectric and piezoelectric properties.Screen-printing enables the easy production of flexible capacitors.To prevent particle aggregation, the BaTiO 3 particles are functionalized with a surfactant.Initially, 60 % vol.BaTiO 3 particles are deposited in the second layer out of three layers.After annealing and cooling, the particle distribution is successfully homogeneous in the whole film.After poling at 80 • C, the relative permittivity and the piezoelectric coefficient d 33 significantly increase up to 159 and 8 pC/N respectively.In situ/operando spatially-resolved X-ray techniques allow exploring the structural evolution of the composite device during annealing and during an applied electric field.The application of an electric field leads to the quasi-disappearance of the P(VDF-TrFE) ferroelectric state.As a matter of fact, the interactions between the P(VDF-TrFE) and the surfactant may limit the rotation of P(VDF-TrFE) chains near the particles.Hence, paraelectric polymers could be chosen on a mechanical or economic basis for the matrix in piezoelectric composite devices.Regarding BaTiO 3 , the lattice strain evolves from an extrinsic strain at RT to an intrinsic strain after annealing and cooling.At the cooled state, the tetragonality c/a is higher than 1.01, leading to improved piezoelectric properties.The increase of the average domain size leads to the increase of the composite permittivity.Finally this knowledge facilitates the development of tailored flexible piezoelectric composite devices.