Highly textured lead-free piezoelectric polycrystals grown by the micro-pulling down freezing technique in the BaTiO3-CaTiO3 system
Highly textured cm-sized (Ba1-xCax)TiO3 (x=0.05) polycrystals at off-eutectic composition were grown by the micro-pulling down freezing technique from the BaTiO3-CaTiO3 system at a high pulling velocity of about 48 mm.h-1. Textured polycrystals exhibiting submillimetre-sized dendrites along the (110)pc growth direction and geometrical grains with (100)pc direction were revealed by a complementary analysis performed by Laue diffraction and EBSD techniques. An average Ca content of about x= 0.0435 was measured throughout the whole volume of the boule and leads to an effective partition coefficient of Ca about 0.87. LIBS measurements highlighted the local segregation of Ca and major impurity contents within dendrites, grains and at the grain boundaries. Dielectric and piezoelectric measurements performed on oriented polycristalline textured samples led to Curie temperatures up to 116°C and d33 up to 214 pC.N-1, in very good agreement with literature values. Both chemical and physical results obtained in the BCT system make µ-PD technique a promising and alternative way to improve the piezoelectric response of lead-free solid solution-based crystals through their texturing along preferential crystallographic directions.