Growth and electrical properties of self-flux method grown (1-x) Bi_(1/2)Na_(1/2)TiO_3-xBaTiO_3 single crystals across the morphotropic phase boundary

摘要

The ferroelectric solid solution 0.94(Bi_(1/2)Na_(1/2))TiO_3-0.06BaTiO_3 (BNBT) is a promising material to substitute the environmentally undesired Pb-based ferroelectrics. Lead-free piezoelectric BNBT bulk size single crystals with a composition across the morphotropic phase boundary (MPB) have been successfully grown by the self-flux method. Powder X-ray diffraction (PXRD) pattern confirms the perovskite structure of the synthesized BNBT crystals. The lattice strain is calculated as 1.7 × 10~(-2) using Williamson-Hall equation from PXRD. The elemental composition of the BNBT single crystals grown with different compositions is confirmed by X-ray fluorescence, covering the rhombohedral to tetragonal region and encompassing the MPB. The presence of a phase boundary between rhombohedral and tetragonal phases near MPB results in electrical behavior enhancement. The dielectric, ferroelectric, and piezoelectric properties along the pseudocubic <001> direction have been measured. Dielectric permittivity gives diffuseness of BNBT crystals and it confirms the relaxor-type behavior. AC conductivity gave the activation energy as 0.46 eV.