Influence of BaTiO 3 Content on the Structure and Properties of Na 0.5 Bi 0.5 TiO 3 Crystals

Lead‐free Na 0.5 Bi 0.5 TiO 3 – x %BaTiO 3 single crystals of different compositions ( x =0, 2, 4, 4.5 and 5.5) were grown using a top‐seeded solution growth method. Temperature‐dependent X‐ray diffraction revealed the presence of a high‐temperature tetragonal phase that existed over a narrow composition range of 0< x <2, at temperatures far in excess of the ferroelectric Curie temperature T c . Polarized light microscopy images confirmed the presence of tetragonal domains in NBT that persisted until T c +250°C; whereas for x >4, rhombohedral domains were found that persisted on heating to only about T c ‐150°C. Investigations of the properties revealed a dramatic increase in the dielectric constant (upto 500%), a decrease in the coercive field (300%), and an increase in the longitudinal piezoelectric constant (1000%) with modest increases in x , as the high‐temperature tetragonal ferroelastic phase was suppressed and as the morphotropic‐phase boundary approached.