Excellent piezoelectric and ferroelectric properties of KNLNTS ceramics with Fe2O3 doping synthesized by the solid state combustion technique

Lead-free piezoelectric (K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3 (KNLNTS) ceramics doped with Fe2O3 at compositions between 0 and 1.0 wt% were prepared by the solid state combustion method with glycine used as the fuel. The effect of Fe2O3 doping on the phase formation, morphology, density, electric and magnetic properties was investigated. The crystal structure of the ceramics doped with Fe2O3 ≤ 0.6 wt% exhibited a pure perovskite phase, while the secondary phases of FeNbO4 and FeTaO4 were detected in the ceramics doped with Fe2O3 > 0.6 wt%. The phase formation changed from orthogonal phase to the dominated orthorhombic phase and cubic phase when Fe2O3 doping increased from 0 to 1.0 wt%. The microstructure exhibited a rectangular shape grain in all samples. The average grain size and the density of the ceramics increased from 1.52 to 2.10 μm and 4.42-4.65 g/cm3 by increasing Fe2O3 content from 0 to 0.6 wt% then dropping in a value with further Fe2O3 doping. The highest dielectric constant (εr at Tr = 2782 and εm at TC = 7520), excellent ferroelectric properties (Pr = 27.9 μC/cm2 and Ec = 9.9 kV/cm) and the highest d33 (311 pC/N) were obtained from the sample doped with 0.6 wt% Fe2O3. This sample exhibited ferromagnetic behavior with Mr and Hc of 0.015 emu/g and 143 Oe, respectively. The dopant of Fe2O3 at appropriate amount and the solid state combustion technique are a new alternative for increment and improvement of densification, microstructure, piezoelectric, ferroelectric and ferromagnetic properties.