Yoshinori Yonesaki

Synthesis, crystal structure, and magnetic properties of Bi3Mn4O12(NO3) oxynitrate comprising S = 3/2 honeycomb lattice.

Neutron diffraction and FT-IR analysis revealed that the novel oxynitrate Bi(3)Mn(4)O(12)(NO(3)) (space group P3, a = 4.9692(1) A, c = 13.1627(3) A) prepared by hydrothermal synthesis is of a new structural type including flat NO(3) layers alternating with blocks of two PbSb(2)O(6)-like layers. Mn(4+) (S = (3)/(2)) forms a regular honeycomb lattice, and magnetic susceptibility data indicated two-dimensional magnetism. Despite its Weiss constant of -257 K, no long-range ordering was observed down to 0.4 K because of the magnetic frustration due to the competition between the nearest and the next-nearest antiferromagnetic interactions.

Preparation of Oriented Titanium Phosphate and Tin Phosphate/ Polyaniline Hybrid Films by Electrochemical Deposition

The preparation of hybrid films of metal (Ti and Sn) phosphate nanosheets and polyaniline by simultaneous electrophoretic and electrolytic deposition was performed in an acetonitrile solvent. Emeraldine polyaniline was intercalated between the phosphate nanosheets with a monolayer arrangement. The obtained hybrid films were several tens of micrometers in thickness. The ratio of incorporated polyaniline to metal phosphate in the hybrid films reaches to around 0.45 and 0.30 at suitable concentrations of tetrabutylammonium hydroxide (TBAOH). These amounts correspond with occupancy of polyaniline in the interlayer gallery of several tens percent. Fractions of voids in a horizontal direction were around 22 and 1% in titanium phosphate/polyaniline and tin phosphate/polyaniline hybrid films, respectively. Thus, anodic electrodeposition makes it possible to form thick films of intercalation compounds of alpha-titanium and tin phosphates with polyaniline. These hybrid films were examined for redox activity. The cyclic voltammetry results of these films confirmed that the hybrid films have redox activity by polyaniline. For these voltammograms, the maximum current was observed in the tin phosphate/polyaniline hybrid deposited for 15 min. The redox activity of these hybrids possibly depends on the mesoscopic texture of the film, especially on the amount of voids in a horizontal direction.

Preparation of Hybrid Film of Polyaniline and Organically Pillared Zirconium Phosphate Nanosheet by Electrodeposition

α-Zirconium phosphate was chemically modified with 1,2-bis(dimethylchlorosilyl)ethane to graft organic chain, and then it was used as host material for inorganic nanosheet-polyaniline hybrid. The grafted α-zirconium phosphate was exfoliated in an acetonitrile solution with tetrabutylammonium salt and aniline. The electrodeposition in the presence of aniline was performed, and then it resulted in a formation of higher-order structure in which phosphate nanosheet was propped up by 1,2-bis(dimethylchlorosilyl)ethane with intrusion of polyaniline into the nanospace. The gravimetric capacitance of the α-zirconium phosphate without grafts and polyaniline hybrid film was around 194 F/g with the base on the amount of polyaniline mass. On the other hand, the α-zirconium phosphate nanosheet with grafts and polyaniline hybrid film provided larger capacitance of around 350 F/g in maximum. The nanospace formed by grafted phosphate nanosheet with 1,2-bis(dimethylchlorosilyl)ethane molecules gives increased amounts of polyaniline included and diffusion paths for ions.

Hydrothermal Synthesis of a New Double Perovskite-Type Bismuthate, (Ba0.75K0.14H0.11)BiO3·nH2O

A new double perovskite-type bismuthate, (Ba0.75K0.14H0.11)BiO3nH2O was prepared by low-temperature hydrothermal reaction. This compound had the double perovskite-type structure with a cubic cell of a = 0.85444(3) nm, in which the A site was occupied by Ba atoms, K atoms, and water molecules, and Bi atoms occupied one crystallographic site. This compound exhibited superconductive diamagnetism with an onset temperature of about 8 K.

Second-harmonic generation in optically poled tellurite glasses doped with V2O5

Second-harmonic generation (SHG) has been observed in optically poled tellurite glasses doped with V2O5. The optical poling has been performed by using the fundamental wave at the wavelength of 1064 nm and the second-harmonic wave at 532 nm from a Nd:YAG pulsed laser. The second-harmonic intensity of 15Nb2O5·85TeO2 glasses containing V2O5 is larger by two orders of magnitude than that of tellurite glass of the same composition without V2O5. Electron spin resonance spectra indicate that vanadium ions are present as either V4+ or V5+, and that the relative amount of V4+ is decreased when the glass is irradiated with second-harmonic waves of a Nd:YLF laser (523 nm) whose wavelength lies in the tail of the intense absorption mainly ascribable to charge transfer in the V5+–O2− bond. We propose a model in which a positive hole and an electron, generated by photo-oxidation of V4+ into V5+ due to two-step photon absorption at 532 nm, bring about a periodic arrangement of electric dipoles and/or periodic alternation of an internal dc electric field, resulting in optically induced SHG in the present tellurite glasses doped with V2O5.

Ferroelectric property of (Ba,Bi)(Ti,M)O3 (M; Cu, Mn, Al, Fe, In, Y, Yb) ceramics

Two types of solid solutions, (Ba1-2xBi2x)(CuxTi1-x)O3 (x ≤ 0.04) and (Ba1-xBix)(MxTi1-x)O3 (M; Al, Mn, Fe, In, Y, Yb; x ≤ 0.03) were prepared by conventional high temperature reaction. For the solid solution of (Ba1-2xBi2x)(CuxTi1-x)O3 single phases with the tetragonal cell was obtained in the region of x ≤ 0.04 and for the solid solutions of (Ba1-xBix)(MxTi1-x)O3 (M; Al, Mn, Fe, In, Y, Yb) single phases with the tetragonal cell was observed in the region of x ≤ 0.03 except the sample of M = Al in which a small amount of the second phase was contained. In these solid solutions the Tc increased with the value of x except for M = Al, and was 144.7°C for x = 0.020 of M = Cu, and the highest Tc was observed for x = 0.020 of every M atom and the order of the highest Tc was Cu (144.7°C), Y (141.4°C), Yb (140.8°C), In (138.5°C), Mn (135.5°C) and Fe (131.3°C). The highest apparent piezoelectric constant, (d33 = 258 pm/V) in these solid solutions was observed for x = 0.010 of Al.

Size–controlled synthesis of β–Co(OH)2 hexagonal nanoplates and their conversion into CoO octahedrons using cobalt naphthenate under solvothermal conditions

β–Co(OH)2 hexagonal nanoplates with a size range from 300 nm to 3 μm have been synthesised successfully by a template and surfactant–free solvothermal route in a very simple system composed only of water, LiOH and cobalt naphthenate in xylene solution. This method is high–yield, simple and environmentally benign. The as–obtained Co(OH)2 hexagonal nanoplates can be easily converted into CoO octahedrons with the size of 15 μm by increasing reaction temperature.

Preparation of α-Fe2O3 particles with controlled shape and size via a facile hydrothermal route

α-Fe2O3 particles with controlled shape and size have been prepared by a facile hydrothermal reaction between ferric chloride hexahydrate (FeCl36H2O) and sodium hydroxide (NaOH) at 160°C. X-ray powder diffraction pattern indicates that the product is single-phase of α-Fe2O3.The morphology of α-Fe2O3 particles changed as homogenous sphere, top-shape and cube, depending on solution pH. Meanwhile, monodispersed cube particles of α-Fe2O3 are also prepared under the same conditions using surfactant of hexadecyl trimethyl ammonium bromide (CTAB). The experimental results suggest that particle size can be controlled by adjusting the solution pH and amount of CTAB.