Jaffari, G. HassnainAkram, M.Zia, LayiqAli, Awais...
8页查看更多>>摘要：Colossal permittivity with low loss tangent has been achieved by co-substitution of Zn and Nb in TiO2. Incor-poration of the divalent and pentavalent ions has been confirmed by structural and Raman spectroscopic analysis. Specific ratio of acceptor-donor pairs led to observation of colossal permittivity (~10(4)) with a low loss tangent (< 0.1). Evidence of localized donor electrons in the dielectric response shows the generation of electron pinned defect dipoles. Low-temperature dielectric relaxation has been observed which correspond to the polaronic conduction following Arrhenius law. As the acceptor-donor content increases, the polaronic relaxation dynamics occurs at higher temperatures. This also reveals that the defect complexes are strongly correlated. Permittivity values corresponding to the loss tangent minima have been compared as a function of acceptor-donor content. Finally, optimum sintering temperature, frequency, measurement temperature, and composi-tion have been identified.
原文链接:
NSTL
Elsevier
Zhu, SiyuHuang, JiananSong, JunfuLiao, Chenxing...
7页查看更多>>摘要：In this work, heavily Er2O3 doped TeO2 glass was employed for the fabrication of transparent glass ceramics with broadband NIR and efficient MIR emissions. The simple composition of the glass was to minimize the refractive index difference between the glass and precipitated crystal to obtain high transmittance glass ceramics with large grain size. The heavily doping concentration was favor to obtain broadband NIR and efficient MIR emissions. The influence of the temperature and duration of the heat treatment on the size of the precipitated Er2Te5O13 crystal was investigated. The transmittance of the glass-ceramics was higher than 80%/mm when the size of the precipitated crystal increased up to 6.82 mu m. The XRD patterns of the surface and bulk glass-ceramic demonstrated the crystallization was surface indued crystallization. The NIR and MIR fluorescence properties were discussed.
原文链接:- NSTL
- Elsevier
Ahmed, HussainMukhtar, SurayyaAgathopoulos, SimeonIlyas, Syed Zafar...
9页查看更多>>摘要：Lead-free perovskite solar cells (PSCs), such as the mixed-halide perovskites (MHPs) ones, are promising devices in order to overcome the inherent problems of instability and toxicity of the lead-based PSCs. This is the first study that reports on Ga-based lead-free mixed halide perovskites with a general formula of Cs3GaI6-xBrx for 0 <= x <= 6, investigated by CASTEP with norm-conserving and Vanderbilt ultrasoft pseudopotentials along the projector augmented wave (PAW) method (for core-level properties) in the framework of density functional theory (DFT). The role of Ga at the B position of the perovskite structure ABX(3) was investigated. The effect of increasing of I concentration was thoroughly determined. The investigated compounds manifest good structural stability and have energy bandgaps close to the Shockley-Queisser limit of 1.34 eV. The bandgaps of Cs3GaI2Br4, Cs3GaI3Br3, Cs3GaI4Br2, and Cs3GaI5Br were calculated as 1.779, 1.615, 1.354, and 1.319 eV, respectively. The optical absorption coefficients of the investigated MHPs lie in the range of 10(4) per cm. Among the investigated materials, Cs3GaI4Br2 and Cs3GaI5Br are recommended for solar cells and other photovoltaic applications.
原文链接:- NSTL
- Elsevier
Sayyed, M. I.Abokhamis, FouzyaAbdulrazzaq, AmnahOzcelik, Bekir...
10页查看更多>>摘要：Zn doped Mg2FeTiO6 double perovskite was synthetized by solid state reaction method with various Zn concentrations. The synthesis process was developed in detail. The XRD analysis shows A-site substitution of Magnesium cations with those of zinc giving the Mg2(1-x)Zn2xFeTiO6 nanopowders of grain size in the order of 20 nm dissolved in monoclinic crystal system of P2(1)/c space group. The magnetization measurement for an applied magnetic field of +/- 10 kOe range at the temperatures 10 and 300 K shows that the Mg2(1-x)Zn2xFeTiO6 nano experienced a transition from ferromagnetic to paramagnetic behavior by varying the Zn-doping percentage. The gamma shielding properties for Mg2(1-x)Zn2xFeTiO6 of the prepared material were assessed experimentally through measured the linear attenuation coefficient (LAC). The mass attenuation coefficient (MAC) values were calculated and compared with XCOM data from LAC values. The Zn-doping percentage enhanced all gamma shielding properties. For example, the LAC at 184 keV records 0.34819, 0.48421, 0.58233, 0.62176, 0.6503, and 0.68917 cm(-1) for CS0, CS0.1, CS0.2, CS0.3, CS0.4, and CS0.5, respectively. In contrast, the mean free path increases from 1.4510 to 3.1374 cm at 184 keV and 810 keV, denoting any system's reduced radiation absorption efficiency with increasing energy. The radiation protection efficiency (RPE) reduced gradually with rising energy, and RBE values for the CS0.5 sample ranged between 96.8121 and 79.6815% at energy 184-810 keV. Based on these results, it is concluded that CS0.5 can be used in the gamma shielding field.
原文链接:- NSTL
- Elsevier
Yu, GuangChen, HanxiaoMa, ShengcanLuo, Xiaohua...
7页查看更多>>摘要：A Mn-vacancy polycrystalline tetragonal Heusler sample Mn1.89Pt0.98Ga1.12 is fabricated in this work. The magnetic and AC-susceptibility measurements validate the existence of reentrant spin glass (RSG) state with the freezing temperature, T-f = 123 K in the alloy. Spontaneous exchange bias is also obtained with the maximum of similar to 47 mT, which should be associated with the coexistence of ferrimagnetic matrix and spin-glass orderings. What's more, a robust and low field topological Hall effect (THE) is achieved in Mn1.89Pt0.98Ga1.12, which is revealed by the hump-like anomaly in the field-dependent Hall resistivity curves. The maximum value of topological Hall resistivity is about 0.366 mu omega middotcm at 5 K. This indicates that there may exist a non-coplanar spin configuration such as anti-skyrmion nucleating and annihilating with applying field, which contributes a non-zero scalar spin chirality. The mutual interplay among possible existence of anti-skyrmion, THE, and RSG in the alloy is discussed.
原文链接:- NSTL
- Elsevier
SanjeevSingh, MukhtiyarKumar, RameshSrivastava, Sunita...
8页查看更多>>摘要：The topological phase tuning in Half-Heusler alloys could be hosted from trivial to non-trivial states and vice-versa, either with a small variation in the lattice parameter or by introducing the spin-orbit coupling. First principles simulations of the electronic bulk band structure of the YPdBi compound exhibit the topologically non-trivial semimetal state without and with spin-orbit coupling at equilibrium lattice constant due to the single band-inversion at Gamma-point. We observed the topological phase tuning from a non-trivial to a trivial state due to the second band-inversion at Gamma-point, after applying the hydrostatic pressure of ~4 GPa. The semimetallic nature of these compounds is protected by the cubic symmetry of the crystal. Thus, by breaking cubic symmetry of the crystal with the application of uniaxial strain along the c-axis and biaxial strain in the ab-plane, we have noticed the topological phase transition from a non-trivial semimetal state to a topological insulator. The importance of half-Heusler compounds lies in their usage as a promising candidate in nanoelectronic applications.
原文链接:- NSTL
- Elsevier
Cheng, MingluoLiang, MinjieLiao, Haihong
6页查看更多>>摘要：The electronic and thermodynamic variation of the delta-Ni3Nb phase with pressure in the range of 0-1200 GPa under hydrostatic pressure was investigated by DFT. By comparing the nucleation phase gamma with the transition phase gamma '', it is found that the magnitude of the stability of the three phases remains the same under 0-1200 GPa, and the difference between the stability of delta and gamma '' phases is small and both are larger than that of gamma. This in- dicates that the delta phase has the precipitation law of gamma -> delta and gamma ''->delta under 0-1200 GPa under hydrostatic pressure. The calculated data show that the results obtained by using the GGA-PW91 generalized function have the smallest error with the experimental value, and the properties of energy, cell volume, density of states, differential charge, elastic constant and phonon of gamma, gamma '' and delta phases are calculated after the convergence of each parameter, and the delta phase is a strongly anisotropic material and the most dense vibration at 4.8 and 6.6 THz frequencies and the heat capacity delta>gamma ''>gamma relationship.
原文链接:- NSTL
- Elsevier
Segovia-Chaves, FrancisVinck-Posada, HerbertNavarro-Baron, E. Petrovish
5页查看更多>>摘要：In this work, we calculate the photonic band structure for a defective two-dimensional photonic crystal with a star defect using the plane wave expansion method and supercell technique. The photonic crystal is composed of triangular scatterers distributed in a honeycomb lattice with an air background. For transverse magnetic polarization, a defect mode was identified in the photonic band gap with the same intensity of the electrical displacement concentrated within the triangles. By calculating the gap map based on triangle lengths, the defect mode is concentrated within the photonic band gap for triangles with lengths of L = 0.48a, wherein a represents the lattice constant. When considering scatterer rotation in the lattice, the photonic band gap is maximized for rotations of theta = pi/6, which generates the presence of two defect modes for transverse electric polarization. Finally, regarding the dependence of the refractive index on the applied pressure, the defect mode is tuned at lower frequencies as pressure increases from 0 to 6 GPa.
原文链接:- NSTL
- Elsevier
Lin, XuelingBai, HongcunYang, ZekunChen, Huanming...
12页查看更多>>摘要：The effect of defective structure taking on the electronic and optical properties of InP nanowire has been investigated. The substitutional and the interstitial doping (X-In, X-P, X-in, X = Zn, Ga, Ge, As, Se) are considered as the defective structures. The results suggested that Zn-In and Ga-In doping induce acceptor levels. Ge-In, As-In and Se-In doping induce donor levels. The Ga-in, Ge-in, As-in and Sein doping induce both donor and acceptor levels, which formed a bridge effect of impurity bands and an orbital hybridization. The absorptive spectra implied that their optical absorption appears an enhanced trend after X-In and X-P doping in the subsurface layer meanwhile the absorption of X-In and XP doping in the core layer are lower than that of original InP nanowire. Therefore, the absorptive property can be improved by X-In and XP doping in the subsurface layer or by Xin interstitial doping.
原文链接:- NSTL
- Elsevier
Rastogi, Chandresh KumarMishra, R. K.Chirauri, SatyakamalRao, K. Ramachandra...
10页查看更多>>摘要：Distinct differences observed in the alternating current powder electroluminescence (ACPEL) and photoluminescence (PL) characteristics of lab-made ZnS:Cu(1%) phosphor have been explained based on variation in donor and acceptor traps (levels) assisted electron-hole recombination upon optical and electrical excitations. The results were also compared with that of commercially available ZnS based phosphor. The fabricated display panel using lab-made ZnS:Cu(1%) sample exhibit bright blue colour electroluminescence. On the other hand, device fabricated using commercially available phosphor display bright cyan colour emission under similar biasing conditions. It is confirmed that the commercially available phosphor is composed of both cubic and hexagonal phases of ZnS whereas the lab-made sample is single phase cubic ZnS. The observed variation in spectral profile for commercial sample with increase in frequency of applied AC signal has been explained based on coexistence of hexagonal and cubic phases of ZnS in the sample.
原文链接:- NSTL
- Elsevier
