Microstructure and dielectric properties of silver–barium titanate nanocomplex materials by wet chemical approach

Abstract

To develop ceramic capacitors with a high effective dielectric constant, we attempted to fabricate BaTiO 3 (BT) complexes with embedded Ag nanoparticles by wet chemical processes. Ag nanoparticle-adsorbed dendritic BT particles, Ag-BT hybrid particles, were synthesized from the solgel-derived precursor gel powders containing Ag, Ba, and Ti by hydrothermal treatment. These particles were pressed with BT fillers and TiO 2 precursor nanoparticles into green compacts, and then, the green compacts were chemically converted into the Ag/BT nanocomplex compacts in Ba(OH) 2 aqueous solution under the hydrothermal condition at 160 °C. The effective dielectric constant of the resultant Ag/BT nanocomplexes increases with an increase in Ag content. The maximal effective dielectric constant of approximately 900 was recorded for the nanocomplex with the Ag content of 10.7 vol %.

Synthesis of Silver-Strontium Titanate Hybrid Nanoparticles by Sol-Gel-Hydrothermal Method

“…Other research groups reported the synthesis of single-crystal BaTiO 3 [ 27 ], Ba 1− x Sr x TiO 3 [ 28 ] and SrTiO 3 dendrites [ 29 ]. We have also reported dendritic Ag-BaTiO 3 hybrid particles by using the gels derived by the sol-gel process [ 15 ]. Such dendritic growth is promoted under the non-equilibrium condition, in which the growth rate of crystals sufficiently exceeds the mass transport rate of ions for the crystal growth (diffusion-limited aggregation phenomena) [ 25 , 27 , 29 , 30 , 31 , 32 ].…”

“…Thus, the local concentration of Ag + ions around the growing SrTiO 3 dendrites increases, and these Ag + ions react with OH − ions and immediately form nanocrystalline precipitates on the surface of SrTiO 3 dendrites. Ag 2 O is expected to be formed in basic aqueous solutions at room temperature, but Ag 2 O is then reduced under the hydrothermal conditions [ 15 ]. As a result of competitive formation reactions of Ag and SrTiO 3 around the precursor gels, Ag nanoparticle-loaded SrTiO 3 hybrid nanoparticles can be obtained.…”

“…In our previous report, we synthesized Ag-BaTiO 3 hybrid particles by the sol-gel-hydrothermal method to fabricate Ag/BaTiO 3 nanocomposite compacts for capacitor applications [ 15 ]. Such metal/insulator composite capacitors with distributed metal particles in the insulator layer have attracted much attention because of their extremely high capacitance over 10 4 [ 16 , 17 , 18 , 19 ], and the distribution state of the metal particles is required to be precisely controlled, that is the metal particles should be insulated by the insulator layer and homogeneously distributed to enhance the dielectric breakdown strength.…”

Preparation of titanium metal/barium titanate composites with boundary layer structure by hydrothermal method and their dielectric properties

“…[1][2][3][4][5] We have also reported metal= insulator composites such as titanium metal=barium titanate (Ti=BT) and silver=BT (Ag=BT) composite materials with effective dielectric constants of over 10 3 , which were prepared by a low-temperature process utilizing hydrothermal reactions below 200 °C. 6,7) These composites are classified as percolation materials, and their dielectric properties are significantly influenced by the distribution state of metal particles. 7,8) However, as it is difficult to homogeneously distribute metal particles in insulator layers, metal=insulator composites with a different structure should be investigated.…”

“…6,7) These composites are classified as percolation materials, and their dielectric properties are significantly influenced by the distribution state of metal particles. 7,8) However, as it is difficult to homogeneously distribute metal particles in insulator layers, metal=insulator composites with a different structure should be investigated. In this study, we focus on the microstructure of boundarylayer (BL) capacitors.…”