Characterization of barium titanate nanoparticles and dense nanograin free-standing films via sol-gel method using highly concentrated alkoxide solution

Abstract

This paper reports on two topics regarding nanosized barium titanate (BaTiO 3 ) prepared by the solgel method using a highly concentrated alkoxides precursor solution. One topic concerns the crystallographic features of the BaTiO 3 nanoparticles. In the case of using a highly concentrated precursor solution, non-coreshell BaTiO 3 nanocrystals with a small amount of intraparticle voids, lattice hydroxyl groups and remaining alkoxy groups were efficiently generated by the addition of less excess water during aging at room temperature. The generation of the high-quality BaTiO 3 nanocrystals is considered to be due to the hydrolysis and polycondensation reaction of the alkoxides being well promoted in such a concentrated solution. The lattice volume of the BaTiO 3 nanocrystals with a crystallite size of 15 nm fired at 600°C was approximately 1 vol % larger than that of bulk crystal. This lattice expansion is more likely to be caused by an intrinsic size effect than an extrinsic effect due to the lattice defects, such as lattice hydroxyl groups. The other topic concerns the dielectric properties of dense nanograin free-standing films with a grain size of 57 nm after applying the same solgel method. Significant frequency dispersion behavior of dissipation factor was observed at temperatures less than the Curie temperature. This finding may indicate that the dielectric properties reflect an intrinsic grain size effect without any influence being attributed to the film/substrate interface or lattice defects.

Innovative nanocrystal-based technologies for ceramic devices with novel electronic functions

“…In Fig. 7 is also shown relaxor-like dielectric properties obtained for a free-standing dense ceramic sheet consisting of BaTiO 3 NCs with a median size of 57 nm [39]. This experimental fact provides a promising clue in considering the NC structures to be constructed for realizing NC devices with novel, gigantic dielectric functions based on relaxor-type dielectric responses.…”

Synthesis of Tetragonal BaTiO₃ Powders via Alkoxide Method Assisted by Diethanolamine

“…With the electronic ceramic devices developing towards micro, thin, and light, a higher standard for the characters such as the powder purity, the particle size, the particle diameter distribution, and the chemical compositions is proposed. Various methods of preparation high-purity ultrafine tetragonal BaTiO 3 powders have been absorbed in experiments by many researchers for improving the properties, such as high temperature solid-state method [2], hydrothermal method [3,4], co-precipitation method [5], microemulsion method [6], and alkoxide method [7,8], etc. Although some successes have been achieved, it is difficult to control the purity and the particle size of the powders by most methods.…”