Temperature-dependent synchrotron powder diffraction phase studies of (K0.37Na0.52Li0.03)(Nb0.87Ta0.1Sb0.03)O3 ferroelectric ceramics

Abstract

Temperature-dependent synchrotron powder diffraction measurements have been performed on leadfree ferroelectric (K0.37Na0.52Li0.03)(Nb0.87Ta0.1Sb0.03)O3 ceramics. The measurement was performed from 20 °C to 400 °C with 20 °C steps. The diffraction patterns showed the existence of two phases from 20 °C to 180 °C while the ferroelectric to paraelectric phase transition occurred between 340 °C and 360 °C. Rietveld refinement using the Fullprof software was employed and the two-phase region was refined using a combination of the orthorhombic phase with space group Amm2 (38) and the tetragonal phase with space group P4mm (99) from 20 °C to 180 °C. The tetragonal phase was used for the refinement up to 340 °C while the cubic phase was refined with space group Pm-3m (221). Good refinement structure parameters were obtained for all temperatures with the average G.O.F being approximately 4.0. Information about the cell parameters and weight fraction of the phases were obtained as a function of temperature