Preparation of grain-oriented Sr0.5Ba0.5Nb2O6 ferroelectric ceramics by magnetic alignment

The properties of polycrystalline ceramics are strongly influenced by their crystallographic texture. In this study, highly grain-oriented tungsten bronze structure ferroelectric ceramics, Sr0.5Ba0.5Nb2O6, were successfully fabricated by magnetic alignment and gelcasting techniques using only the conventional solid-state-synthesized starting powder. Spherical Sr0.5Ba0.5Nb2O6 particles were aligned according to their anisotropic magnetic property in 40 vol% slurry in a 10 T magnetic field, and then in situ locked by polymerization via a gelcasting technique for 30 min. A < 00l >-axis orientation perpendicular to the magnetic field direction (B) was obviously observed in the green compact and sintered sample. The sintered Sr0.5Ba0.5Nb2O6 sample contained equiaxial grains and reached 98% theoretical density. Compared with the sample with randomly oriented grains, the magnetically aligned sample showed an enhanced with dielectric constant in the perpendicular to B direction (1100 versus 750 at room temperature and 4300 versus 2800 at Curie temperature). This new method is readily applicable to other ceramics with tungsten bronze structure, and is expected to facilitate mass preparation of large and dense grain-oriented ceramic materials.