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B arium titanate and/or barium strontium titanate thin films have been in increasing demand as ferroelectric materials for the fabrication of ferroelectric memory devices, 1 multilayer capacitors, 2 optical modulators, 3 and other devices. Paraelectric thin films are attractive dielectrics for use in decoupling capacitors and high-frequency voltage-tunable microwave circuits, such as voltage-controlled oscillators (VCOs), tunable filters, and phase shifters. 4 In recent years, there has been increasing interest in the synthesis of artificial superlattices of oxide materials because they have the potential to drastically improve ferroelectric properties. 5 Many studies concerning the SrTiO 3 /Ba-TiO 3 system 6À9 have succeeded in fabricating artificial superlattices. Their superlattices have shown behaviors different from those of solid solution Ba x Sr 1Àx TiO 3 (BST).Artificial superlattices of oxide materials have been prepared by various vapor deposition techniques, such as RF sputtering, 10,11 pulsed laser deposition, 12,13 and molecular beam epitaxy. 14,15 To improve the dielectric properties of perovskite-type artificial superlattices, the thickness of the layer must be less than 10 nm, and each layer must grow highly epitaxially. Vapor deposition techniques are suitable for preparing thin films with thicknesses of less than 10 nm because these techniques can deposit at the atomic level. Nevertheless, to our knowledge, there has been no report on highly oriented SrTiO 3 /BaTiO 3 artificial superlattices with a thickness of less than 10 nm prepared by the chemical solution deposition (CSD) method. CSD of BaTiO 3 or SrTiO 3 at temperatures of approximately 600À800 °C typically results in a polycrystalline, granular film because of the trend toward homogeneous nucleation in the pyrolyzed precursor. 16À18 The CSD method utilized for the

As the BaTiO3 dielectric layer of multi-layer ceramic capacitors (MLCCs) becomes thinner, the problem of leakage current degradation arises. In this study, the leakage current degradation was investigated for the cases when the Ni–Sn internal electrode was placed at either the anode or the cathode. The MLCCs with the Ni–Sn internal electrode at the anode suppressed the leakage current degradation with time significantly better than that at the cathode. The leakage current types for the degraded MLCCs were tunnel and Schottky or Poole–Frenkel for the Ni and Ni–Sn internal electrodes, respectively. High-resolution scanning transmission electron microscopy revealed an interface layer with a high Sn concentration at the interface between the Ni–Sn internal electrode and BaTiO3. Therefore, the interface of the electrode at the anode plays an important role in the leakage current degradation of MLCCs with time.

Epitaxial assembly involved in the formation of aggregates of single-crystalline barium titanate (BaTiO 3 ) nanoparticles under hydrothermal condition is reported. The aggregates of BaTiO 3 nanocrystals were synthesized by heating a mixture of barium hydroxide, Ba(OH) 2 , and titanium tetra-iso-propoxide, Ti(O i C 3 H 7 ) 4 , with a molar ratio of 1:1 : 1 resolved in water-ethanol solutions at 150 C for 2 h in autoclaves. The volume ratio of water/ethanol used as the solvent gives a significant influence on the amount of organic components contained in the precipitates after the reaction completed; a pure water solution left much organic components in the obtained BaTiO 3 nanoparticles aggregates, whereas a 1 : 1 (in volume ratio) water-ethanol solution yielded aggregates of BaTiO 3 nanoparticles with little organic components. Transmission electron microscopy (TEM) analyses provide definite evidence for the occurrence of epitaxial assembly of more than hundred BaTiO 3 nanocrystals with sizes of 40 -60 nm into an aggregation possessing crystallographically single-crystalline nature during the crystal growth under the hydrothermal condition.

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