Phase transition behaviour and dielectric properties of Na 0.5 K 0.5 NbO 3 -LiTaO 3 -LiSbO 3 lead-free piezoceramic

Lead-free piezoelectric ceramics have attracted considerable attention as new piezoelectric materials for replacing Pb(Zr,Ti)O3 (PZT)-based ceramics because of environmental protection reasons. Among lead-free piezoelectric systems, the ternary system of Na0.5K0.5NbO3-LiTaO3-LiSbO3 has proven to be an outstanding lead-free piezoceramic with properties almost comparable to undoped PZT. In this study, addition of LiSbO3 to the 0.95 Na0.5K0.5NbO3- 0.05 LiTaO3 lead-free piezoceramic composition showed a change from an orthorhombic to a tetragonal crystal system in samples prepared by reaction-sintering. The limit of solid solution along the compositional join, (0.95 x)Na0.5K0.5NbO3- 0.05 LiTaO3-x LiSbO3, occurred at x 0.06. Differential scanning calorimetry analysis and measurements of dielectric constant as a function of temperature indicated broad Curie peaks from which it was inferred that the samples were not chemically homogeneous. Curie temperatures decreased from 425 °C for x = 0, to 345 °C for the limiting x = 0.06 composition. Improvement of dielectric properties was obtained for LiSbO3 modified samples. Microstructures exhibited secondary recrystallization, with LiSbO3 addition giving rise to a small reduction in average grain size.