Synthesis, phase confirmation and electrical properties of (1-x)KNNS-xBNZSH lead-free ceramics

In the present work, lead-free piezoelectric ceramics (Rx)(K0.5Na0.5)(Nb0.96Sb0.04O3)-x(Bi0.5Na0.5)(Zr0.8Sn0.1Hf0.1)O-3 [abb. as (Rx)KNNS-xBNZSH, 0 <= x <= 0.04] were prepared via solid-state sintering technique. The thermal behavior of mixed powders has been investigated for x = 0, 0.02, and 0.04 using TGA-DSC analysis to estimate the calcination temperature. The structural, morphological, dielectric, ferroelectric and piezoelectric properties are analyzed through the appropriate characterization techniques. The X-ray diffraction (XRD) patterns demonstrate a pure perovskite phase structure for all the sintered samples. Further, the coexistence of rhombohedral to orthorhombic (R-O) phase is observed in ceramic sample with x = 0.02. The morphology of all the sintered samples exhibits an inhomogeneous, dense microstructure with the rectangular grain, while for x = 0.02, a relatively homogeneous distribution of grains is observed. BNZSH doping decreases the average grain size from 2.22 to 0.33 mu m for x = 0 to x = 0.04, respectively. Owing to the presence of multiple-phase coexistence as well as the improved microstructure and enhanced dielectric properties (dielectric constant epsilon(r) = 1080, epsilon(max) = 5301; Curie temperature - T-C similar to 317 degrees C; dielectric loss - tan delta similar to 6%) the ceramics with x = 0.02 has been found to have a large piezoelectric coefficient (d(33)) of similar to 180 pC/N, remnant polarization (P-r) similar to 16.7 mu C/cm(2) and coercive field (E-c) similar to 10.7 kV/cm. We believe it will expand the range of applications for KNN-based ceramics.