Key Engineering Materials Vol. 485

Abstract: ZnO films with controlled microstructures and crystal orientations were fabricated on nonseeded substrates by a spin-spray method employing tri-sodium citrate as a structure-directing agent at 90°C. The microstructure of the films changed from a rod array to a dense film by addition of the tri-sodium citrate in the solution. The FT-IR spectra of the films prepared with citrate contained organic molecules including carboxyl groups, being attributed to citric ion. Surface analysis by XPS indicated that the adsorbed citric ions were estimated to form zinc-citrate complex including ammonium ion or ammonium citrate.

Abstract: Three and six LiTaO₃ single crystals are used to achieve continuous emission of high-intensity X-rays. Furthermore, the interaction between X-rays and the case of the X-ray source is used to generate electrons. X-rays were emitted continuously and fluctuations in the count rate were reduced when three or six crystals were used. Moreover, the X-ray intensity increased and the number of electrons generated by the above-mentioned interaction increased with increasing number of crystals.

Abstract: We investigated the crystallization and resulting morphology of a stoichiometric barium-silicate glass 1BaO-2SiO₂ (glassy sanbornite) by using transmission electron microscope and Raman spectroscopy. A crystalline aggregate structure consisting of a Ba₅Si₈O₂₁ phase (trunk) and a β-BaSi₂O₅ phase (branch) was observed in the heat-treated glassy sanbornite. The Ba-richer phase of Ba₅Si₈O₂₁ precipitated prior to the formation of the stoichiometric β-BaSi₂O₅ phase, suggesting the presence of the region in which the Ba ions are enriched or cohesively distributed. A considerable structural similarity between the glassy sanbornite and the Ba₅Si₈O₂₁ phase was also suggested in this study.

Abstract: Nucleation and particle growth conditions of barium titanate (BaTiO₃, BT) were investigated for preparation of the BT/strontium titanate (SrTiO₃, ST) multilayered nanoparticles. The conditions with and without BT nucleation were clarified. Epitaxial growth of the BT layer on the ST substrate particles was studied using both conditions. The formation of the BT layer on the ST substrate particles was confirmed using the condition with BT nucleation.

Abstract: Nanocubes accumulations were built up by meniscus method and developed to achieve a dense structure. For the first attempt, strontium titanate (SrTiO₃, ST) nanocubes were selected for the nanocubes accumulations. The ST nanocubes were prepared by a solvothermal method. For Strontium titanate nanocubes, Sr(OH)₂ and titanium isopropoxide (TP) were used as starting materials and were heated at 240°C for 18h in an autoclave. Size distribution of TP-derived ST nanocubes was narrower than TiO₂-derived ST nanocubes. Moreover ST nanocubes accumulations were prepared by a meniscus method. A dense ST nanocubes accumulation of over 1 μm was prepared at an angle of 50 degrees at 60 °C. The crystal structures were determined by X-ray diffraction (XRD) and the microstructures were observed by scanning electron microscopy (SEM).

Abstract: Grain-oriented Barium titanate (BaTiO₃) ceramics were prepared using an electrophoresis deposition (EPD) method under high magnetic field of 12 T and sintering at 1350 °C. It was found that BT03 and BTKK nanoparticles were necessary to synthesize the grain-oriented BT ceramics. The grain orientation was correlated with particles size and c/a ratio of lattice constants. The reason why the grain-oriented BT ceramics using the BT03 and BTKK were prepared was having the large values of the particles size and the c/a ration of lattice constants.

Abstract: We prepared glasses in 30BaO-(15+x)TiO₂-(55–x)GeO₂ composition (x=0, 10, 20, 35) and examined their crystallization behavior. Relation of crystallizing-phase to optical transparency in the resulting crystallized sample was also considered. Although the glass samples with x=0-20, which precipitate fresnoite-type Ba₂TiGe₂O₈ as main phase, lost transparency after crystallization, the glass with x=30, which precipitates BaTi₄O₉ phase, kept good transparency. Dependence of transparency on the x is also discussed.

Abstract: Bicolor perovskite superlattices (LaNb2O₇)_nL(Ca₂Nb₃O₁₀)_nC have been successfully fabricated by a layer-by-layer assembly using two different perovskite nanosheets (LaNb2O₇ and Ca₂Nb₃O₁₀) as a building block. The artificially fabricated (LaNb2O₇)_nL(Ca₂Nb₃O₁₀)_nC superlattices are structurally unique, which is not feasible to create in the bulk form.

Abstract: We succeeded in the single crystal growth of Ba₂SiO₄:Eu²⁺ by novel synthesis method which was gas (SiO) and solid (Ba - Sc - Al - Eu - O) phase hybridized. The Ba₂SiO₄:Eu²⁺ single crystal was synthesized by interfacial crystal growth after the reaction of the SiO gas with the surface of Ba - Sc - Al - Eu - O substrate in the reductive atmosphere. The single crystals were plate-like crystals with about 500 μm sizes and emitted green light around 500 nm under 300 - 450 nm excitation.