Growth and Optical Properties of Lead-Free Barium Bismuth Sodium Titanate Crystals Near Morphotropic Phase Boundary

Lead-free materials (1-x)(Na_0.5Bi_0.5)TiO_3-xBaTiO₃ (NBT-xBT) have morphotropic phase boundary structure. Here the NBT-xBT single crystals with different compositions were fabricated by optimized top-seeded solution growth method. Relationship between the composition, orientation and optical properties of the single crystals near morphotropic phase boundary structure was studied. Transmittance of 001-poled tetragonal NBT-xBT single crystal reaches 70%. The transmittance of crystals depends on the domain configuration after poled. Refractive indices of the crystals poled along 001 direction were measured at room temperature, and dispersion equations were fitted. Refractive index increases rapidly as the wavelength decreases. These studies are helpful to the development of environmentally friendly optical devices.