Rumi Tanahashi

POTASSIUM-SODIUM-RUBIDIUM NIOBATE SINGLE CRYSTALS AND ELECTRIC PROPERTIES

Potassium-sodium-rubidium niobate single crystals are grown using an original pulling down method, to improve their composition change during a crystal growth, by means of co-doping of small ionic size sodium and large ionic size rubidium into potassium niobate. Even by the co-doping, single crystals can be grown with orthorhombic single-phase at room temperature, as well as pure potassium niobate. Their electric properties, such as the dielectric constant and the impedance, are changed depending on the doping ions.

Crystal Growth and Electric Properties of Bismuth Titanate Fibers

Bismuth titanate (Bi4Ti3O12) crystals were grown by our original floating-zone pulling down (Fz-PD) method. The shape of the grown crystals was fiberlike with dimensions of 15×1×0.34 mm3. The dielectric properties and impedance of the grown fiber crystals were determined. A large difference in the dielectric constant was observed along the c- and a-axes.

Density of states, magnetic and transport properties of Nd doped two dimensional perovskite compound Sr2CoO4

Structures, transport, magnetic properties, and first principle calculation results will be reported for the two dimensional layered structured perovskite compounds Sr2-xNdxCoO4 (x = 0.5, 0.75, 1, 1.25). Structure refinement results revealed that these compounds crystallized in K2NiF4-type structures with space group I4/mmm. The temperature dependence of resistivity showed semiconductor like behavior for these samples. It was found that the lattice parameter c decreases as the doping level x increases. The compounds exhibited a paramagnetic to ferromagnetic transition at temperatures of about 170, 125 K for the x = 1 and 0.75 samples, respectively. The temperature dependence of resistivity for the samples can be well fitted by the 2D variable hoping (VRH) model ρ = ρo exp(T0/T)1/3 (where ρo is a material specific characteristic conductance, with unit Ω−1, T0 is a material specific characteristic temperature in K) over the whole measured temperature range. First principles calculations indicated that the N...

Synthesis of KNbO3 Films from K2NbO3F Solution on Oxide Substrates

Method to synthesize KNbO3 crystals using K2NbO3F solutions is of interest. In this paper, films of KNbO3 crystals are synthesized on several oxide substrates from K2NbO3F solutions. The films have some orientation due to a reaction with the substrates. The reason is expected the solution after the synthesis is strongly basic.

Li(Ga1-xMx)O2 (M: B or Al) Single Crystals Grown by Floating Zone Method

Li(Ga1-xMx)O2 (M: B or Al) single crystals are grown by Floating zone method. These crystals are characterized from the viewpoint of the substitution of M, such as lattice parameter (lattice volume) change, piezoelectric properties and nonlinear optics. The lattice volume is decreased with the increase of Al content for Al-substitution largely, but the change is a little for B-substitution.