| Abstract [eng] |
Due to environmental regulations against high amounts of lead used in ferroelectric materials (RoHS directive in EU), a lot of studies have been done in order to find the best lead-free alternatives. Na0.5Bi0.5TiO3 (NBT) -based compositions possess quite large dielectric permittivity values and high electromechanical strain. One of the most prominent techniques to create multi-layered ceramic structures is tape casting. This technology can provide high-quality, large-area and thin functional materials, such as ferroelectrics, piezoelectrics for multilayered capacitors. Tape casting is mostly based on non-aqueous solvent, but aqueous-based tape casting is also used as a simple and eco-friendly method. In this work, thick films of Bi-stoichiometric NBT doped with 1 % of Yb ((Na0.5Bi0.49Yb0.01)TiO3), Bi-overstoichiometric (Na0.5Bi0.51Yb0.01)TiO3 and pure NBT were prepared by tape casting. The films were produced via an aqueous tape casting method. Dispex AA4040 was used as a surfactant and PVP solution (Luvitec K 90 Pulver) – as a binder. Two-step thermal treatment (at 500 oC and at 1200 oC (2 h)) on platinum substrate, was followed by the casting and drying. The obtained films were of 170 um thickness. Dielectric properties were measured at a temperature range 30 K - 750 K upon cooling with a rate of 1 K/min. Also, electromechanical properties were investigated using commercial aixaCCT TF 2000 analyzer. Results of this work showed that Bi-overstoichiometric NBYT film has better piezoelectric properties than Bi-stoichiometric NBYT and NBT films. In other hand Bi-stoichiometric NBYT films do not have low-temperature depolarization. This property is useful for high-temperature applications. |
