Shinichi Furusawa

TEM Observation and Ionic Conductivity Study of Li2SiO3 Thin-Film on Sapphire Substrate

Thin-film samples of the lithium ionic conductor Li2SiO3 (LSO) were deposited on an A-plane sapphire substrate via the pulsed laser deposition (PLD) method, and the irreversible temperature dependence of the ionic conductivity in the thin-film samples was studied. Via transmission electron microscopy (TEM) observations of annealed LSO thin-film, it was found that the as-prepared LSO thin-film was amorphous over the temperature range T 490 K, and that nanocrystals existed in the annealed LSO thin-film in the temperature range T 550 K. Further more, it was clarified the irreversible temperature dependence of the ionic conductivity is due to the generation of nanocrystals.

Ionic Conductivity of Li2ZnTi3O8 Single Crystal

Single crystals of lithium zinc titanate (Li2ZnTi3O8) were grown in a double-mirror type optical floating-zone furnace for the first time. Single crystals were characterized by X-ray powder diffraction and Laue measurements. The ionic conductivity of the single crystals was measured in the temperature range of 400–700 K. Below 600 K, the ionic conductivity of the single crystal is one to two orders of magnitude higher than that of polycrystalline Li2ZnTi3O8. In the temperature range of 550–600 K, the temperature dependence of the ionic conductivity shows non-Arrhenius behaviour.

Ionic Conductivity of Polycrystalline Li2GexSi1-xO3 (x = 0.0~1.0)

Polycrystalline Li2GexSi1-xO3 (x = 0.0~1.0) was synthesized by solid state reaction, and its ionic conductivity was studied as a function of x in a temperature range of 500–700 K. The ionic conductivity was found to depend on x and was enhanced at x = 0.2–0.7. Furthermore, the pre-exponential factor and activation energy in the Arrhenius equation were also found to depend on x. These results suggest that lithium ionic conduction in Li2GexSi1-xO3 is strongly influenced by the structure of the framework.

Synthesis and Ionic Conductivity of KAlSi3O8

In this study, KAlSi3O8 was synthesized by a solid-phase reaction at 900, 1000 and 1100 °C, using K2CO3, Al2O3 and SiO2 as the starting materials. The powder X-ray diffraction profile of the compound thus prepared was confirmed to contain a mixture of crystalline and glass phases. In addition, a higher sintering temperature of greater than 1000 °C possibly led to the decrease in the crystalline phase. From the temperature dependence of dc conductivity, activation energies for ionic transport were estimated to be 0.79–0.84 eV. The frequency-dependence of the real part of electrical conductivity suggests that the mechanism of ionic transport in the dispersion region possibly depends on the crystallinity of KAlSi3O8.

Synthesis of MnZn-Ferrite Using Coprecipitation Method

Mn1-xZnxFe2O4 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) are synthesized using sintering coprecipitation method. The coprecipitation retains from 0 hours to 48 hours at 1200 °C. The synthesis of a Mn0.6Zn0.4Fe2O4 is almost completed even though retaining time is for 0 hours at 1200 °C. The crystal growth of Mn0.6Zn0.4Fe2O4 particles proceeds rapidly retaining up to 6 hours and saturates retaining more than 6 hours at 1200 °C. The permeability and the electric resistivity are affected by the crystal growth of Mn0.6Zn0.4Fe2O4 particles.

Synthesis of MnZn-Ferrite Using Sintering Aids

Mn0.7Zn0.3Fe2O4 is synthesized by sintering the nanosize precursor with sintering aids, which is synthesized by the coprecipitation method. The crystal growth of Mn0.7Zn0.3Fe2O4 is controlled by the amount of sintering aids. Complex permeability is explained by the Maxwell-Garnett (MG) effective medium model. The ferromagnetic resonance frequency more than 1 GHz can be explained by the shape anisotropy under the sintering process of the Mn0.7Zn0.3Fe2O4 particles. These results suggest possibility of Mn0.7Zn0.3Fe2O4 as a high frequency device material.

Electrical Conductivity of Li2xZn2-3xTi1+xO4 Crystal

Li2xZn2-3xTi1+xO4 (x=0.33, 0.50, 0.60) crystals were grown in a double-mirror type optical floating-zone furnace. The electrical conductivity of Li2xZn2-3xTi1+xO4 of crystal was measured in a frequency range from 100 Hz to 10 MHz and in a temperature range from 330 to 700 K, in nitrogen gas. It was revealed the electrical conductivity mechanism changes at the temperature region of 480520 K. The electrical conductivity of polycrystalline Li2xZn2-3xTi1+xO4 (x=0.6) shows nearly two orders of magnitude higher values compared to other samples.

Ferromagnetic Resonance Frequency of Single-Layer Magnetic Metal Films with Lattice Distortion

The ferromagnetic resonance frequency of single-layer magnetic films has been investigated in relation to lattice distortion. It is found that the ferromagnetic resonance frequency depends on a lattice distortion. This result raises the possibility of tuning the ferromagnetic resonance frequency by controlling the lattice distortion.