The effect of sintering temperature and time on the growth of single crystals of 0.75 (Na0.5Bi0.5)TiO3-0.25 SrTiO3 by solid state crystal growth

Materials in the (Na0.5Bi0.5)TiO3-SrTiO3 system are of interest for use as lead-free piezoelectric actuators due to high electric-field induced strains. Piezoelectric properties may be further improved by growing single crystals but as yet work on single crystal growth in this system is limited. In the present work, single crystals of composition 0.75 (Na0.5Bi0.5)TiO(3-)0.25 SrTiO3 were grown by solid state crystal growth (SSCG) on [001] SrTiO3 seed crystals and the dependence of crystal growth distance and matrix grain growth on sintering temperature investigated. Electron backscattered diffraction and X-ray diffraction analysis show that the single crystals grow epitaxially on the seed crystals. Energy dispersive spectroscopy indicates that the grown crystals are slightly Na-deficient, while X-ray photoelectron spectroscopy indicates the presence of oxygen vacancies. Single crystal growth distance, mean matrix grain size and grain size distribution as a function of sintering temperature and time are presented. Increasing the sintering temperature increases both single crystal and matrix grain growth rates. The optimum single crystal growth temperature is found to be 1250A degrees C. The effect of sintering temperature on the single crystal and matrix grain growth behavior is explained using the mixed control mechanism of microstructural evolution.