Electrical Properties of Textured Niobium‐Doped Bismuth Titanate Ceramics

Abstract

Crystallographically textured Nb‐doped bismuth titanate ceramics Bi4Ti(3−x)NbxO12, were fabricated by tape casting using plate‐like Bi4Ti3O12 particles prepared by a molten‐salt method as the templates. The templates were aligned in the fine‐grained matrix by aqueous tape casting with their major surface parallel to the casting plane. Effect of niobium on the grain orientation in the material was investigated. It was found that the use of a fine precursor powder led to enhanced densification of the ceramic, while Nb doping reduced electrical conduction and dielectric loss, which enabled poling at high temperatures and high electric fields. The textured Bi4Ti3O12 ceramic showed a high anisotropy in its dielectric properties in the directions parallel and perpendicular to the casting plane. Highly textured BiT was obtained with the use of only 5 wt% of template particles by sintering at 800°C for 1 h.

Influence of processing route on electrical properties of Bi4Ti3O12 ceramics obtained by tape-casting technology

“…Elongated grains in the form of platelets with homogeneous and packaged distribution that is a typical structure of bismuth with layered compounds Aurivillius type were observed by the PPM. According to Aguiar et al [4] the SEM images of the randomly oriented samples exhibit mixed grain microstructures of equiaxed and platelike grains for BIT samples. The surface of the BIT pellets obtained by SSR was platelike with lengths ranging from 5 to 6 mm and a width of 1 mm while the surface of the pellet obtained by the PPM showed a rounded grains shape.…”

“…Bismuth titanate (Bi 4 Ti 3 O 12 ) is a well-known member of the bismuth oxide layer structure ferroelectrics. It is a candidate for high-temperature piezoelectric applications, memory storage, and optical displays because of its high Curie temperature of 675 C [1][2][3] and electrooptic switching behavior [4][5][6][7][8][9][10][11][12][13]. Its structure is formed by Bi 2 O 2 layers separated by Bi 2 Ti 3 O 12 layer with orthorhombic structure at room temperature.…”

“…Meanwhile, the problem of the hard particle agglomerate can be still present resulting in poor microstructure and properties of the Bi 4 Ti 3 O 12 ceramics. The novelty of present work in comparison with previous ones [4] is to evaluate the solid-state reactions initiated by intensive milling in high-energy ball mills as an alternative for the ceramic powder preparation. An important criterion for intensive milling is the formation of highly dispersed phased materials typical for metal powders or oxide based materials (mechanical activation) or the formation of new product because of a solid-state reaction (mechanochemical synthesis).…”