Impedance Spectroscopy of Lead-Free Ferroelectric Coatings

Pyroelectric Properties of BaxSr(1-x)TiO3/PVDF-TrFE Coating on Silicon

Bilayer coatings of barium strontium titanate (Ba_xSr_(1-x)TiO₃)/poly [(vinylidenefluoride-co-trifluoroethylene] (PVDF-TrFE) were integrated on silicon Si (100) for pyroelectric devices. Pyroelectric properties of the composite were determined for different electrode materials (silver and aluminum) and different electrodes configurations creating an electric field in parallel and in-plane direction in the ferroelectric coating. For this purpose, parallel-plate and planar interdigital capacitors were fabricated. Anisotropy in the pyroelectric response was noted for the different directions of the measured electrical potential. The dynamic method was used to evaluate the pyroelectric properties in the temperature range of 22 to 48 °C. Pyroelectric response with a higher value was observed at the one plate's configuration of interdigital electrodes. The voltage response was the strongest when silver contacts were used. At temperatures near room temperature, the voltage increased by 182 µV at resolution of 7 µV/°C for the in-plain device configuration, vs. 290 µV at a resolution of 11 µV/°C for the out-of-plain configuration. A relationship between the surface morphology of the ferroelectric oxide and oxide/polymer coating and the pyroelectric voltage was also found, proving the smoothening effect of the introduction of polymer PVDF-TrFE over the BaSrTiO₃ grains.