High Strain Response and Dielectric Properties of Bi1/2(Na0.78K0.22)1/2TiO3 Ceramics Doped with (Fe1/2Nb1/2)4+

Environmentally friendly piezoceramics Bi-1/2(Na0.78K0.22)(1/2)Ti1-x(Fe1/2Nb1/2)(x)O-3 (BNKT-FN) with FeNb (FN) ratios 0, 0.01, 0.02, 0.03 and 0.04 were synthesized via conventional solid-state reaction (CSSR). X-ray diffraction (XRD) analysis revealed that the FN complexes were completely dissolved in BNKT perovskite and the structural transition occurred from ferroelectric to relaxor state. The average grain sizes for x = 0, 0.01, 0.02, 0.03 and 0.04 were found to be 0.34 mu m, 0.35 mu m, 0.38 mu m, 0.32 mu m and 0.39 mu m, respectively. It is observed that the grain size increased with the addition of FN, except for x = 0.03. The coercive field (E-c) and remnant polarization (P-r) of the system were decreased with increasing FN concentration and the highest E-c of 21.1 kV/cm and P-r of 29.2 mu C/cm(2) were noted for the base pure sample. In addition, the increase of FN content steadily broadened the dielectric anomaly at maximum dielectric constant temperature (T-m) in the BNKT-FN system. Consequently, unipolar normalized strain (S-max/E-max) was found to be enhanced monotonically achieving the highest value of around 654 pm/V (x = 0.02). These properties suggest that the investigated system could be a promising eco-friendly candidate for piezoelectric actuators and many other applications requiring high piezoelectric induced strain.