Goncharenko, Anatoliy V.Venger, Eugene F.Pinchuk, Anatoliy O.
6页查看更多>>摘要：While traditional and widely accepted mixing rules are based on the concept of a fixed inclusion shape, real particle composites are usually shape-distributed. For such composite materials, however, the analytical homogenization techniques are not well developed, while their numerical analysis becomes particularly complicated. We introduce and analyze two analytical models for the effective conductivity of a particular class of two-phase composites, namely those containing shape-distributed rigid inclusions. The models are derived with the use of the Bergman-Milton spectral density function approach. As we show, one of them, which involves the Gauss hypergeometric function, provides reasonable agreement with experimental data within the wide range of filling factors for ion-exchange resin beads in aqueous solutions. Another model, which is based on the uniform spectral density function, gives rise to a logarithmic singularity for the effective conductivity at the percolation threshold.
原文链接:
NSTL
Elsevier
Xie, ZhuojiaZou, ZhengguangJiang, XinyuZhang, Weijian...
10页查看更多>>摘要：In this study, La0.7Sr0.2Nd0.1Mn1-xNixO3 (x = 0.05, 0.10, 0.15) systems were synthesized following the sol-gel (SG) approach and their structural, magnetic, and magnetocaloric characteristics were determined. The X-ray Diffraction (XRD) patterns revealed that all samples were in the R-3c space group. Magnetic studies revealed that an increase in the Ni2+ dopant resulted in a ferromagnetic (FM) to paramagnetic (PM) transition near the Curie temperature (Tc), when Tc decreased from 280 K to 220 K. The maximum change in magnetic entropy (- Delta S-M(Max) gradually decreased while the relative cooling power (RCP) gradually increased. The -Delta S-M(Max) and RCP values for La0.7Sr0.2Nd0.1Mn0.95Ni0.05O3 were 4.28 J/(kg.K) and 267.67 (J/kg), respectively at 280 K when the external magnetic field variation was 5 T. This material can potentially be one of the candidates for developing the magnetic refrigeration technology.
原文链接:- NSTL
- Elsevier
Chang, CengLi, XuechaoDuan, YimingZhao, Zhuang...
6页查看更多>>摘要：In this paper, the effects of hydrostatic pressure, temperature, Al-concentration and other structural parameters on the optical absorption coefficients (OACs) in inversely quadratic Yukawa-Herman potential (IQYHP) GaAs/ Al eta Ga1_eta As spherical quantum dots are studied theoretically. The Nikiforov-Uvarov (N-U) solution is used to solve the Schro center dot dinger equation corresponding to this structure, and the energy levels and wave functions can be obtained. We also get nonlinear optical absorption coefficients by using compact density matrix theory and iterative method. The results show that various parameters play an essential role in OACs, including the red shift (blue shift) of OACs resonance peaks and the change of peaks size.
原文链接:- NSTL
- Elsevier
Yin, ChengpingWu, FengZhang, XuanLiu, Dejun...
8页查看更多>>摘要：Phase manipulation plays a fundamental role in both optical physics and devices. It is known that the phase shift at the band edges in all-dielectric one-dimensional (1-D) photonic crystals (PCs) is near 0 or pi due to the Bragg scattering mechanism. However, the band edges in all-dielectric 1-D PCs shift toward shorter wavelengths as the incident angle increases, which rules out the possibility to realize angle-insensitive (i.e., omnidirectional) phase shift. Herein, we utilize the angle-insensitive property of the band edge in a 1-D PC containing hyperbolic metamaterials to achieve angle-insensitive phase shift in the visible range. At the wavelength around the angle-insensitive band edge, the phase shift remains near zero in the incident angle range from 0 to near 90 degrees. Our work provides a route, under the current experimental conditions, to controlling phase shift.
原文链接:- NSTL
- Elsevier
Sarmah, SikhaBorah, RitupanMaji, P. K.Ravi, S....
21页查看更多>>摘要：The structural, magnetic and dielectric properties of Co(Fe1-xAlx)(2)O-4 (x = 0, 0.02, 0.05, 0.15 and 0.20) synthesized by sol-gel method sintered at 1100 ?C have been reported. Structural analysis from the XRD patterns and FT-IR measurements confirms the formation of single phase spinel structure. The saturation magnetization de-creases with Al3+ substitution with the exception of x = 0.02 sample. The x = 0.02 sample exhibits an enhanced value of saturation magnetization, due to the cationic re-distribution within the tetrahedral and octahedral sites. The coercive field is found to be prominently influenced by magnetocrystalline anisotropy. The dielectric constant decreases with Al3+ substitution. For x = 0.20 sample, the dielectric constant shows a sharp rise around 1 MHz due to LC resonance effect between the sample and measuring leads. The study of ac conductivity suggests that above 383 K, the conduction mechanism does not follow Jonschers' Power law, exhibited by most spinel ferrites.
原文链接:- NSTL
- Elsevier
Zhao, YongmingWang, LeiLiu, JiandongLei, Dandan...
6页查看更多>>摘要：We report the magnetic and magnetocaloric properties of two Gd-based compounds. First, for the orthorhombic lattice compound GdFeTiO5, no signature of long-range magnetic ordering is observed down to 2 K. The maximum magnetic entropy change (-delta S-M(max)) is derived to be 18.9 J kg(-1)K(-1) at 3 K for 0-3 T and 33.6 J kg(-1) K(-1)at 5 K for 0-7 T, respectively, which is attributed to the rotation of spins of weakly ferromagnetically coupled Gd3+/Fe(3+ )ions toward the external magnetic field. Second, a new honeycomb layered tellurate GdMnTeO(6 )is synthesized. The compound crystallizes in a trigonal structure with space group P-31c and is long-range antiferromagnetically ordered at TN = 7.0 K. The value of -delta S-M(max) at TN is about 14.8 J kg(-1) K-1 for 0-3 T and 29.8 J kg(-1) K-1 for 0-7 T, respectively, which is associated with field-induced antiferromagnetic to ferromagnetic transition. Thus, with the large value of -delta S-M(max) and the absence of thermal and field hysteresis, both Gd compounds are candidates for low-temperature magnetocaloric materials. In relative to GdFeTiO5, the reduction of MCE in GdMnTeO6 might be associated with antiferromagnetic order.
原文链接:- NSTL
- Elsevier
Amorri, O.Slimi, H.Oueslati, A.Aydi, A....
10页查看更多>>摘要：The spinel ferrite material families are subjected to diverse studies according to their wide field application. In this work, the LiCd0.5Fe2O4 ferrite was successfully synthesized by a conventional solid-state method. The structural, optical, electrical and dielectric characterizations were treated. The Rietveld refinement method explored cubic spinel structure (Fd(sic)m space group) with a lattice parameter: a = 8.628 angstrom, alpha = 90 degrees. Besides, the surface micrograph shows a strong agglomeration of the grains. Optical results were calculated using diffuse reflectance data and Kubelka Munk theory. They show the semiconductor nature with a band gap around 2.9 eV and Urbach energy around 0.14 eV. The electrical measurements were studied over a range of frequency (40 Hz-1 MHz) and through large temperature scale (200 K-380 K) using the complex impedance spectroscopy technique. The AC conductivity behavior was described by the jump relaxation model, which obeys to the Jonscher's law. The complex impedance analysis has suggested the presence of the contribution of the grains, the grain boundaries and interface in the conduction mechanism. A reduction in real part Z' was observed as a function of temperature and frequency, which indicates an increase in ac conductivity and a negative temperature coefficient of resistance. Hence, the complex modulus plots have affirmed the presence of grain boundaries contribution in the material. Both the complex modulus and impedance investigations have confirmed that the synthesized material exhibits a non-Debye type of relaxation. Finally, the dielectric behavior of the studied sample shows a polarization effect and the permittivity graphs are fitted theoretically with the Cole-Cole model.
原文链接:- NSTL
- Elsevier
Kishor, C. H. RajSreelakshmy, T.Das, AnkitAneesh, P. M....
7页查看更多>>摘要：Semiconductor heterostructures are considered as the building block of advanced semiconductor devices. Here we report the fabrication of p-CuI/n-ZnO heterojunction using the solution-processed spin-coating technique. The structural, morphological and optical properties of the synthesised CuI nanostructures, CuI and ZnO thin films were studied using XRD, FESEM and UV-Visible spectroscopy. XRD studies confirm the formation of zinc blende gamma-CuI nanostructures. The CuI thin films without any impurity phases were deposited and the band gap was found to be in the range of 2.86-2.95 eV. The ZnO thin films were grown by spin coating show hexagonal wurtzite structure from the XRD studies. The optical band gap of the ZnO thin films was obtained to be 3.27 eV. The J-V measurement of the p-CuI/n-ZnO heterojunction confirms the rectifying behaviour. A variation in the ideality factor at different voltage ranges is identified, attributed to the dominance of diffusion and recombination current.
原文链接:- NSTL
- Elsevier
