Search results for "Efficient"

(La0.8Sr0.2)(Mn1−yFey)O3±δ oxides for ITSOFC cathode materials?

2005

The oxygen transport properties in (La 0.8 Sr 0.2 )(Mn 1-y Fe y )O 3±δ (LSMF) with various iron contents y = 0, 0.2, 0.5, 0.8 and 1 were determined by the IEDP technique. Both oxygen diffusion and surface exchange coefficients were found to be greater for y = 0.8 and 1 than those of LSM (y=0). Moreover, for y ≤0.5, grain boundary diffusion was the rate limiting step especially at lower temperatures. Thus, in the LSMF perovskite materials, the oxygen diffusion via oxygen vacancies is enhanced by Fe. The LSMF electrical performances were measured by impedance spectroscopy. Compared to LSM and LSF (y= 1), porous LSMF cathodes with y= 0.2-0.8 exhibit poor electronic conductivity: Fe, by reducin…

APPROXIMATION FOR THE ABSORPTION COEFFICIENT OF ATMOSPHERIC AEROSOL PARTICLES IN TERMS OF MEASURABLE BULK PROPERTIES

1976

Pressure effects on the electronic and optical properties ofAWO4wolframites (A =Cd, Mg, Mn, and Zn): The distinctive behavior of multiferroic MnWO4

2012

The electronic band-structure and band-gap dependence on the $d$ character of ${A}^{2+}$ cation in $A$WO${}_{4}$ wolframite-type oxides is investigated for different compounds ($A$ $=$ Mg, Zn, Cd, and Mn) by means of optical-absorption spectroscopy and first-principles density-functional calculations. High pressure is used to tune their properties up to 10 GPa by changing the bonding distances establishing electronic to structural correlations. The effect of unfilled $d$ levels is found to produce changes in the nature of the band gap as well as its pressure dependence without structural changes. Thus, whereas Mg, Zn, and Cd, with empty or filled $d$ electron shells, give rise to direct and…

Enhanced thermoelectric properties of lightly Nb doped SrTiO3 thin films

2021

Novel thermoelectric materials developed for operation at room temperature must have similar or better performance along with being as ecofriendly as those commercially used, e.g., BiTe, in terms of their toxicity and cost. In this work, we present an in-depth study of the thermoelectric properties of epitaxial Nb-doped strontium titanate (SrTiNbO) thin films as a function of (i) doping concentration, (ii) film thickness and (iii) substrate type. The excellent crystal quality was confirmed by high resolution transmission electron microscopy and X-ray diffraction analysis. The thermoelectric properties were measured by the three-omega method (thermal conductivity) and van der Pauw method (el…

Temperature dependence of refractive index and absorption coefficient of GaSe at 633 nm

1995

Abstract Measurements of the ordinary refractive index and the absorption coefficient ( E /t] to c axis ) of gallium selenide at 633 nm, in the temperature range [20,100] °C, are reported. Useful analytical approximations obtained after a least squares fitting process are provided, as well. These results are basic for any theoretical model of nonlinear and bistable optical devices based on GaSe.

Calculations on solvents and co-solvents of single-wall carbon nanotubes: Cyclopyranoses

2005

Abstract (10,10) single-wall carbon nanotube (SWNT) presents consistency between relatively small solubility, and great partition coefficients and kinetic stability. Solubility of SWNTs is investigated in a variety of solvents, finding a class of non-hydrogen-bonding Lewis bases that provides good solubility. Electron affinity of d -glucopyranoses ( d -Glcpn) suggests colloids of negatively charged SWNTs in water.

Flexural strength and microhardness of anterior composites after accelerated aging

2016

Background This study aimed to evaluate the flexural strength and microhardness of three different anterior composites after 10 000 thermocycles. Material and Methods The mechanical properties of a nano-fill composite (Filtek Ultimate Universal Restorative (FUR) (Enamel)), a nano-hybrid composite (Clearfil Majesty ES2 (ES2) (Enamel)), and a micro-hybrid composite (G Aenial Anterior (GAA)) were investigated in this study. For the microhardness test, 8-mm diameter and 2-mm thickness composite discs were used (n = 10), and for the flexural strength test, 25x2x2 mm bar-shaped specimens were prepared (n = 13). The specimens were tested at 24 h and after 10 000 thermocycles. Data were analyzed us…

Electronic structure and optical, mechanical, and transport properties of the pure, electron-doped, and hole-doped Heusler compound CoTiSb

2012

The Heusler compound CoTiSb was synthesized and investigated theoretically and experimentally with respect to electronic structure and optical, mechanical, and vibrational properties. The optical properties were investigated in a wide spectral range from 10 meV to 6.5 eV and compared with ab initio calculations. The optical spectra confirm the semiconducting nature of CoTiSb, with a strong exciton absorption at 1.83 eV. The calculated phonon dispersion as well as elastic constants verify the mechanical stability of CoTiSb in the cubic $C{1}_{b}$ system. Furthermore, solid solution series of CoTi${}_{1\ensuremath{-}x}$${M}_{x}$Sb ($M=\text{Sc}$, V and $0\ensuremath{\leqslant}x\ensuremath{\le…

Optical properties of wurtzite and rock-salt ZnO under pressure

2005

Abstract This paper reports on the pressure dependence of the optical absorption edge of ZnO in the wurtzite and rock-salt phase, up to 14 GPa. Both vapor-phase monocrystals and pulsed-laser-deposition thin films have been investigated. In both types of samples the wurtzite to rock-salt transition is observed at 9.7±0.2 GPa. The absorption tail of the fundamental gap, as measured in monocrystals, exhibits a pressure coefficient of 24.5±2 meV/GPa. The evolution under pressure of the full absorption edge of the wurtzite phase is studied with thin film samples, yielding a slightly lower pressure coefficient (23.0±0.5 meV/GPa for the A–B exciton). Rock-salt ZnO is shown to be an indirect semico…

Electronic transport properties of electron- and hole-doped semiconductingC1bHeusler compounds:NiTi1−xMxSn(M=Sc,V)

2010

The substitutional series of Heusler compounds ${\text{NiTi}}_{1\ensuremath{-}x}{M}_{x}\text{Sn}$ (where $M=\text{Sc},\text{V}$ and $0lx\ensuremath{\le}0.2$) were synthesized and investigated with respect to their electronic structure and transport properties. The results show the possibility to create $n$-type and $p$-type thermoelectrics within one Heusler compound. The electronic structure and transport properties were calculated by all-electron ab initio methods and compared to the measurements. Hard x-ray photoelectron spectroscopy was carried out and the results are compared to the calculated electronic structure. Pure NiTiSn exhibits massive ``in gap'' states containing about 0.1 ele…