Okayamalite, Ca2B2SiO7, tetragonal, P21m, a = 7.116, c = 4.815 Å, Z = 2, is a new member of melilite group, the boron analogue of gehlenite. Electron microprobe analysis gave CaO 46.28, B2O3 28.50, SiO2 24.24, Al2O3 0.36, total 99.38 wt.%, corresponding to Ca2.01B2.00Si0.98Al0.02O7, a natural counterpart of Ca2B2SiO7 known only synthetically. The strongest lines in the X-ray powder diffraction pattern are 3.479 (40)(111), 2.862 (55)(201), 2.654 (100)(211), 2.129 (20)(301), 1.920 (35)(212), 1.644 (29)(312), very close to those of the synthetic material (a = 7.115, and c = 4.812 ). It is creamy white in colour with an earthy appearance due to the fine grain size. Streak white, cleavage not observed. Hardness ∼5½. Density calculated on the ideal formula is 3.30 g/cm3. It is optically uniaxial negative with ω = 1.700, and ɛ = 1.696. It occurs as patches of a few millimetres across in grey homogeneous-looking aggregate of wollastonite, vesuvianite, calcite and johnbaumite from Fuka mine, Bicchu-cho, Okayama Prefecture, Japan. The patches consist of very fine grains of the mineral up to 30 μm. Okayamalite is considered to be a product after the reaction formula: CaCO3 + CaSiO3 + B2O3 = Ca2B2SiO7 + CO2, arising from boron metasomatism of a wollastonite-calcite aggregate. The name is for the prefecture.

In order to study the oriented aggregation of BaTiO3nanocrystals in the ultrasound-assisted synthesis in an aqueous solution [F.Dang et al., Jpn.J.Appl.Phys. 48, 09KC02 (2009)], the electric dipole-dipole interaction model has been studied by numerical simulations. The results of the numerical simulations are consistent with the experimental ones if the electric dipole moment of a primary particle (a nanocrystal) of 5 nm in diameter is about 10 D =3.3 x 10-29 (C m). It suggests that a 5-10 nm BaTiO3 nanocrystal synthesized in an aqueous solution with ultrasound has spontaneous polarization.

New strategies for materials fabrication are of fundamental importance in the advancement of science and technology. Nanocrystals, especially with an anisotropic shape such as cubic, are candidates for building blocks for new bottom-up approaches to materials assembly, yielding a functional architecture. Such materials also receive attention because of their intrinsic size-dependent properties and resulting applications. Here, we report synthesis and characteristics of BaTiO3 and SrTiO3 nanocubes and the ordered assemblies as ferroelectric supracrystals. BaTiO3 and SrTiO3 nanocubes with narrow size distributions were obtained in an aqueous process. BaTiO3 films made up of ordered nanocube assemblies were fabricated on various substrates by evaporation-induced self-assembly method. Regardless of the substrate, the nanocubes exhibited {100} orientations and a high degree of face-to-face ordering, which remained even after heat treatment at 850 °C. Piezoresponse force microscopy was carried out on the supracrsytal films to obtain plots of the d33 piezoelectric coefficient against the poling field, and ferroelectric hysteresis curves were shown.

A highly crystallized and smooth-surfaced zirconia (ZrO2) thin film was prepared using a precursor solution with 2,4-pentanedione addition (molar ratio of 1:1 for zirconium alkoxide); the film was irradiated with ultraviolet (UV) light using an ultrahigh-pressure mercury lamp. This thin film was compared with another thin film, which prepared using a precursor solution without additives and UV irradiation. The crystallinity of ZrO2 thin films improved with increasing 2,4-pentanedione addition and UV irradiation time and changed according to the type of organic additives. These results occurred presumably because the orientation of polymerization in zirconium alkoxide units and stability of chelate compounds for UV irradiation were controlled under these conditions. In addition, the method was effective for lower-temperature crystallization of highly crystallized, smooth-surfaced thin films.

Wavelength dependence was observed in the ultraviolet (UV) irradiation-assisted crystallization of alkoxy-derived ZrO2 thin films. The surface grains of thin films deposited on Si(100) substrates became enlarged by UV irradiation using an ultrahigh-pressure mercury lamp. The crystallinity of thin films deposited on Si(100) substrates was improved by UV irradiation using a low-pressure mercury lamp. The reaction using the ultrahigh-pressure mercury lamp depended on the substrate type.

A 650 °C annealed thin film was found to be a single phase of SrBi2Ta2O9 (SBT) and showed the c-axis orientation without ultraviolet irradiation. The crystallinity and crystal orientation of the thin films were improved by ultraviolet irradiation using an ultrahigh-pressure mercury lamp (UHPML) or a low-pressure mercury lamp (LPML) under three conditions. In particular, the crystal orientation of the 650 °C annealed thin films dramatically changed by ultraviolet irradiation using a LPML at room temperature or using an UHPML at 150 °C. The 650 °C annealed SBT thin film prepared by ultraviolet irradiation using an UHPML at 150 °C showed a remanent polarization (Pr) of 4.3 μC/cm2 and a coercive electric field (Ec) of 101 kV/cm at 10 V.

c-axis-oriented SrBi2Ta2O9 thin films with various thickness ranging from 20–170 nm were epitaxially grown on (100)SrRuO3 (SrRuO3 is give for the pseudo-cubic unit cell)//(100)SrTiO3 substrates by metalorganic chemical vapor deposition (MOCVD). The relative dielectric constants of these films kept a constant value of about 55 with decreasing film thickness down to 20 nm. The capacitances of these films were almost independent of the applied electric field; change of capacitance for these films on applied electric field from 0 kV/cm to 100 kV/cm was within 0.017 % and tano value was within 1.3 %. The leakage current densities were constant against the film thickness on the order of 10-8 A/cm2 at 150 kV/cm. Surface flatness of these films were also almost the same irrespective of the film thickness. These characteristics are very attractive for high-capacitance condenser application. Therefore, c-axis-oriented BLSF thin films are novel candidates for high-capacitance condenser application having both bias-free and thickness independent characteristics together with the good surface smoothness.

The phase transition of non ferroelectric pyrochlore to ferroelectric perovskite in CaBi4Ti4O15 thin films depended on matching of the atomic arrangements in platinum bottom electrodes to the Ca-Bi-Ti-O thin films. CaBi4Ti4O15 thin films crystallized on (200)-oriented platinum at 650°C showed c-axis orientation. In contrast, thin films randomly crystallized on highly crystalline (111)-oriented platinum at the same temperature contained pyrochlore phase and showed P-V hysteresis loops. The ferroelectric properties improved with the degrees of (h00) orientation.

CaBi2Ta2O9 (CBT) thin films were successfully prepared on Pt-passivated quartz glass substrates using a triple-alkoxide solution. The thin film crystallized to a single phase of perovskite at 750°C via a mixture of fluorite and perovskite phases. The 750°C-annealed thin film showed random orientation and consisted of fine grains with a diameter of about 80 nm. The dielectric constant and loss factor were 124 and 0.04, respectively, and were constant in the frequency range of 10 kHz to 1 MHz. The thin film exhibited P-E hysteresis loops at relatively high voltages. The remanent polarization and coercive electric field were 6.9 μC/cm2 and 170 kV/cm at 13 V, respectivey. The fatigue behaviors against various electric pulse sequences were examined. The polarization did not change when the pulse width was short such as 10-6 s, however, it increased gradually with number of switching cycles when the pulse width was relatively long such as 10-3 s.

LiNbO3 and LiTaO3 are very attractive and useful materials, which have been applied to piezoelectric and electro-optic devices. The authors have synthesized the stoichiometric crystalline fine powders and films of LiNbO3 at temperatures as low as 250°C by the controlled hydrolysis of double alkoxide solutions; and this method was used to prepare Li(Nb, Ta)O3 solid solution films with and without the preferred orientation. Water used during the processing played an important role in the low-temperature crystallization and the elimination of free carbon in the films. The water for the partial hydrolysis affected the properties of alkoxide solutions for dip-coating, and the morphologies of crystalline films. Water in a mixed gas flow with oxygen during calcination accelerated the crystallization of the alkoxy-derived films at low temperatures.