Dielectric anisotropy and sinterability improvement of Ba4Nd9.33Ti18O54 textured ceramics

The 〈0 0 1〉-textured Ba4Nd9.33Ti18O54 (BNdT) ceramics were fabricated by templated grain growth process. Acicular particles prepared using K2SO4 molten salt were used as template and aligned by tape casting in the equiaxed BNdT powder. Crystalline phases of sintered specimen exhibited {h k 0} and {0 0 1} development in the plane of parallel and perpendicular to the casting direction, respectively. The formation of a slight amount of secondary phase in the template particles and the compositional deviation inhibited the densification and texture development for BNdT. To improve the sinterability, the composition shifted from BNdT to Ba2Ti9O20 (B2T9) rich side slightly in BaONd2O3TiO2 ternary system, which enables to promote a liquid phase during the sintering, was examined as a matrix phase. Resultant ceramics including B2T9-rich matrix phase displayed high density and large dielectric anisotropy. Temperature dependence of dielectric constant showed negative and positive behavior between the direction of parallel and perpendicular to the 〈0 0 1〉-textured BNdT. Near-zero temperature coefficient of resonant frequency (τf) in TE0 1 1 mode was obtained in the textured ceramics with the degree of {0 0 1} orientation of approximately 0.37 on the disk plane. The exceptional temperature behavior of BNdT made it possible to control the τf over the wide range by the combination of dielectric anisotropy.