Comprehensive investigation of microstructure, electrical and photocatalytic properties of ${\text{K}}_{{{\text{0}}{\text{.5}}}} {\text{Na}}_{{{\text{0}}{\text{.5}}}} {\text{NbO}}_{{\text{3}}}$ lead- free ceramics prepared via different synthesis routes

Abstract

The comprehensive study on the impact of different synthesis techniques on the structural, electrical, and photocatalytic properties of perovskite ferroelectric ceramics ${\text{K}}_{0.5}{\text{N}\text{a}}_{0.5}{\text{N}\text{b}\text{O}}_{3}$(KNN). The solid-state reaction and hydrothermal methods are used to prepare the KNN ceramics, and the effects of grain size on the physical characteristics these ceramics are examined. The KNN-S prepared by solid-state method have significantly larger grain size as compared to that for KNN-H prepared by hydrothermal method. Furthermore, the KNN-S is found to exhibit higher dielectric, piezoelectric and ferroelectric properties as compared to KNN-H. On the other hand, the increased photocatalytic activity is observed in KNN-H as compared to KNN-S. As compared to the hydrothermal synthesis, the solid-state synthesis causes an increase in the relative dielectric permittivity $\left({\epsilon }^{{\prime }}\right)$ from 2394 to 3286, remnant polarization $\left({P}_{r}\right)$ from 15.38 to 20.41 ${\upmu }$C/${\text{c}\text{m}}^{2}$, planer electromechanical coupling factor $\left({k}_{p}\right)$ from 0.19 to 0.28 and piezoelectric coefficient $\left({d}_{33}\right)$ from 88 to 125 pC/N. The KNN-S ceramics are also found to have a lower leakage current density, and higher grain resistance than KNN-H ceramic. The enhanced photocatalytic activity of KNN-H is attributed to relatively smaller particle sizes. The KNN-S and KNN-H samples are found to have degradation efficiencies of RhB solution of 20% and 65%, respectively. The study highlights the importance of synthesis methods and how these can be exploited to tailor the dielectric, piezoelectric and photocatalytic properties of KNN.