Improvement in temperature stability and modified polymorphic phase transition of La-doped (Na0.52K0.44Li0.04) Nb0.8Ta0.2O3 lead-free piezoelectric ceramics

Abstract

Lead-free ceramics (Na0.52K0.44Li0.04)1-3xLaxNb0.8Ta0.2O3 (KNLNT-Lax, x=0.00–1.25mol%) were prepared by traditional method. The piezoelectric proprieties and the polymorphic phase transition behaviors around the room temperature were investigated. The results show that high density (ρ~95%) and outstanding piezoelectric performance (d33≥200pC/N, kp≥40%) were obtained with 0.5–0.75mol% La doping. By the research of temperature dependent εr, Δfr/fr20°C, and kp, we acquired the extended and mild polymorphic phase transition region, and obvious improvement of temperature stability in −50–80°C with the maximum derivation d(Δfr/fr20°C)max less than 2%, as the La doping content exceeds 0.5mol%. The possible mechanism of enhanced properties and temperature stability was analyzed. Both excellent piezoelectric and temperature stability characteristics make the La-doped KNLNT ceramics feasible for practical applications.