The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

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A comprehensive review of zno materials and devices

Metal hydride materials for solid hydrogen storage: a review

This review focuses on key aspects of the thermal decomposition of multinary or mixed hydride materials, with a particular emphasis on the rational control and chemical tuning of the strategically important thermal decomposition temperature of such hydrides, Tdec. An attempt is also made to predict the thermal stability of as-yet unknown, elusive or even unknown hydrides. The future of a particularly promising class of materials for hydrogen storage, namely the catalytically enhanced complex metal hydrides, is discussed. The predictions are supported by thermodynamics considerations, calculations derived from molecular orbital (MO) theory and backed up by simple chemical insights and intuition.

Thermal decomposition of the non-interstitial hydrides for the storage and production of hydrogen.

Hydrogen storage in Mg: A most promising material

Recently a significant figure-of-merit (ZT) improvement in the most-studied existing thermoelectric materials has been achieved by creating nanograins and nanostructures in the grains using the combination of high-energy ball milling and a direct-current-induced hot-press process. Thermoelectric transport measurements, coupled with microstructure studies and theoretical modeling, show that the ZT improvement is the result of low lattice thermal conductivity due to the increased phonon scattering by grain boundaries and structural defects. In this article, the synthesis process and the relationship between the microstructures and the thermoelectric properties of the nanostructured thermoelectric bulk materials with an enhanced ZT value are reviewed. It is expected that the nanostructured materials described here will be useful for a variety of applications such as waste heat recovery, solar energy conversion, and environmentally friendly refrigeration.

Enhancement of Thermoelectric Figure-of-Merit by a Bulk Nanostructuring Approach

A new ternary magnesium–titanium hydride Mg7TiHx with hydrogen desorption properties better than both binary magnesium and titanium hydrides

We have examined the phase equilibrium and thermoelectric properties of Co1−xFexSb3 ternary system up to high iron context x=0.40. Traces of Sb were observed in the hot-pressed samples with x⩾0.06, and FeSb2 (Fe0.73Co0.27Sb2) compound with marcasite structure was also observed in the samples with x⩾0.25 by x-ray diffraction. The lattice parameter of Co1−xFexSb3 is slightly larger than that of the binary compound CoSb3. The Seebeck coefficient and the electrical resistivity are generally reduced by the substitution for Co by Fe. The thermal conductivity is also reduced by the substitution especially at high iron content region. These behaviors of the thermoelectric properties in the samples with low iron content are ascribed to the substituted Fe, while those in the samples with high iron content are ascribed to the precipitated FeSb2 (Fe0.73Co0.27Sb2) compound. For x⩽0.04, the figure of merit for Co1−xFexSb3 decreases with increasing x. However, above x=0.06 the figure of merit increases with x and as a r...

Thermoelectric properties of the skutterudite Co1−xFexSb3 system

Synthesis of NaxCo2O4 thermoelectric oxides by the polymerized complex method

A RAID-group converting apparatus converts two RAID groups into one RAID group. The RAID-group converting apparatus includes: a data-reading unit that reads at least non-parity data from data including the non-parity data and parity data, for each stripe from a plurality of recording media belonging to the two RAID groups; a parity-generating unit that generates two parities using the data belonging to a same stripe read by the data-reading unit; and a parity-writing unit that writes the two parities generated by the parity-generating unit into a parity storage area belonging to the same stripe.

Raid-group converting apparatus and method

(Zn1−yMgy)1−xAlxO powders were synthesized by the polymerized complex method and then consolidated by spark plasma sintering apparatus. The microscopic structure and thermoelectric properties were examined comparing with the experimental results of the samples prepared by the conventional solid-state reaction method. A small amount of ZnAl2O4 spinel phase as the second phase was observed in the sintered samples with x⩾0.02 by x-ray diffraction and a scanning electron microscope. The grain size of the samples prepared by the polymerized complex method is much smaller than that of the samples prepared by the conventional solid-state reaction method. The absolute values of the Seebeck coefficient and electrical resistivity decrease with increasing x up to about x=0.01, but above x=0.01 they are almost independent of x. This result indicates that the solubility limit of Al in Zn1−xAlxO is about x=0.01, which is also confirmed by 27Al nuclear magnetic resonance spectroscopy. At a fixed composition of x, the ab...

Mikio Ito

Papers

A new ternary magnesium–titanium hydride Mg7TiHx with hydrogen desorption properties better than both binary magnesium and titanium hydrides

Thermoelectric properties of the skutterudite Co1−xFexSb3 system

Synthesis of NaxCo2O4 thermoelectric oxides by the polymerized complex method

Raid-group converting apparatus and method

Thermoelectric properties of (Zn1−yMgy)1−xAlxO ceramics prepared by the polymerized complex method