Crystal structure,ion transport and optical properties of new high-conductivity Ag7(Si1 − xGex)S5I solid solutions

Journal of Materials Science - The crystal structure of Ag7(Si0.8Ge0.2)S5I, Ag7(Si0.6Ge0.4)S5I, Ag7(Si0.4Ge0.6)S5I and Ag7(Si0.2Ge0.8)S5I solid electrolytes, grown by vertical zone crystallization...     

Preparation,electronic structure and optical properties of CoxLaMg1−xAl11O19 microcrystals

Journal of Materials Science: Materials in Electronics - Co-doped LaMgAl11O19 microcrystals were synthesized by a facile sol–gel method. The as-synthesized microcrystals were near hexagonal...     

Structural, transport, magnetic, and dielectric properties of La1−x Te x MnO3 (x = 0.10 and 0.15)

In this study, we have investigated the structure, temperature-dependent resistivity, magnetization, and dielectric properties of La_1?x Te _x MnO_3±δ (x = 0.10 and 0.15). X-ray diffraction analysis confirms the rhombohedral crystal symmetry with space group R $ \overline{3} $ c. For both the samples, the temperature dependence of magnetization plots show paramagnetic-to-ferromagnetic phase transition. The Curie temperature (T _c) and magnitude of magnetization increase with the Te concentration. Field-dependent magnetization produces the asymmetric hysteresis loop that has been attributed to the magneto crystalline anisotropy induced by lattice distortion and the rare earth spin coupling at room temperature. Temperature-dependent resistivity plots exhibit metal–insulator transition (MIT) and charge-ordering state. These plots have been fitted using variable range hopping model, and the density of states [N(E_F)] has been estimated. Magnetoresistance is measured as a function of temperature in the field of 1T, 5T, and 8T. The dielectric constant shows an anomaly near MIT. The dielectric constant exhibits a peaking behavior with the applied frequency and the temperature dependence of dielectric constant attains colossal values at high temperatures.     

Structural and electronic properties of hydrogen adsorptions on BC₃ sheet and graphene: a comparative study

We have systematically investigated the effect of hydrogen adsorption on a single BC? sheet as well as graphene using first-principles calculations. Specifically, a comparative study of the energetically favorable atomic configurations for both H-adsorbed BC? sheets and graphene at different hydrogen concentrations ranging from 1/32 to 4/32 ML and 1/8 to 1 ML was undertaken. The preferred hydrogen arrangement on the single BC? sheet and graphene was found to have the same property as that of the adsorbed H atoms on the neighboring C atoms on the opposite sides of the sheet. Moreover, at low coverage of H, the pattern of hydrogen adsorption on the BC? shows a proclivity toward formation on the same ring, contrasting their behavior on graphene where they tend to form the elongated zigzag chains instead. Lastly, both the hydrogenated BC? sheet and graphene exhibit alternation of semiconducting and metallic properties as the H concentration is increased. These results suggest the possibility of manipulating the bandgaps in a single BC? sheet and graphene by controlling the H concentrations on the BC? sheet and graphene.     

Eu(3+) doped gadolinium oxysulfide (Gd(2)O(2)S) nanostructures-synthesis and optical and electronic properties

One-dimensional Eu(3+) doped gadolinium oxysulfide (Gd(2)O(2)S:Eu(3+)) nanotubes/nanorods have been synthesized via precursors of Gd(OH)(3) nanostructures using a hydrothermal technique. The blue-shifts in the optical spectra for the Gd(2)O(2)S:Eu(3+) system corresponding to the fundamental absorption and Eu(3+)-X(2-) ligand (X = O/S) charge transfer bands (CTBs) are significant (～0.22-0.36?eV) with respect to the bulk counterpart. The nanotubes are good candidates for investigating the size-induced electrical and optical properties of functional oxysulfides. In order to identify the origin and nature of the electronic transitions observed in the visible region, optical and photo-induced impedance measurements have been extended to the nanotubes in this report.     

First-principles calculations of crystal structure,electronic structure and optical properties of Ba<Subscript>2</Subscript>RETaO<Subscript>6</Subscript> (RE = Y,La, Pr,Sm, Gd)

The crystal structure, electronic structure and optical properties of Ba₂RETaO₆ (RE?=?Y, La, Pr, Sm, Gd) have been studied by first-principles calculation. The calculated lattice parameters are in good agreement with the previously reported values. With increasing the atomic number of RE (i.e., the number of 4f electrons), the energy level of RE 4f bands becomes lower continuously. The relationship between the electronic structure and optical properties is explored based on first-principles calculation. The electron transitions between O 2p states, RE 4f states and Ta 5d states have a key effect on optical properties such as dielectric function, refractive index, absorption coefficient and reflectivity. The phase structures have great influence on the optical properties of Ba₂SmTaO₆ and Ba₂GdTaO₆, and the big variation of reflectivity induced from phase transition makes them have potential applications in the infrared radiation protection area.     

Optoelectronic and thermoelectric properties of KAuX5 (X = S, Se): a first principles study

The electronic structure as well as optical and thermoelectric properties of the orthorhombic polychalcogenides of gold KAuX₅ (X = S, Se) compounds have been investigated using full-potential linearized augmented plane wave within the framework of the density functional theory (DFT). The local density approximation (LDA), generalized gradient approximation (GGA) by Perdew, Burke and Ernzerhof (PBE), Engel–Vosko generalized gradient approximation (EV-GGA), and the recently modified Becke–Johnson approximation (mBJ) formalism are used for the exchange correlation energy to calculate the total energy. The results show that KAuX₅ (X = S, Se) is a direct band gap semiconductor at Γ–Γ point. The total and partial density of states indicate that the states Au-d, S-p, and Se-p of both compounds have strong contributions to valence band in the energy range from ?10 up to 0.0 eV. One can notice from electronic charge density that both compounds show greater iconicity and smaller covalency. Optical properties with photon incident energy up to 14.0 eV have been calculated and analyzed. Important transport properties such as Seebeck coefficients as well as thermal and electrical conductivities and effective mass are obtained and discussed in details.     

Nanoarchitectonics of Ba0.97La0.02Ti1-xNb4x/5O3 (x = 0.00 and 0.10) polycrystalline compounds with electrical and optical properties

Journal of Materials Science: Materials in Electronics - A lead-free solid solution, of a composition Ba0.97La0.02Ti1-xNb4x/5O3 (for x?=?0.00 and 0.10) (noted BLT, BLT0.9Nb0.08), was...     

Structural,magnetic, and electrical properties of RFeO3 (R = Dy,Ho, Yb & Lu) compounds

Journal of Materials Science: Materials in Electronics - In this research, the nanosized rare-earth orthoferrites (RFeO3) with R?=?Dy, Ho, Yb &amp; Lu were synthesized by...     

Electronic band structure and optoelectronic properties of SrCu2X2 (X = As,Sb): DFT calculation

All-electron-full potential linear-augmented plane wave method with Engel Vosko approximation was used for calculating the electronic structure, Fermi surface, and optical properties of SrCu₂X₂ (X = As, Sb). The calculated band structure and Fermi surface show that the metallic behavior of SrCu₂X₂ increases as one move from As to Sb. The calculated partial density of states shows that As-s/p/d, Cu-s/p, and Sr-s/p/d states are forming the Fermi surface for SrCu₂As₂, whereas Sb-s/p/d, Cu-s/p, and Sr-s/p/d states are forming the Fermi surface for SrCu₂Sb₂. The calculated densities of states at Fermi level and electronic specific heat are 14.2 (42.57) states/Ryd-cell and 2.60 (7.37) mJ/mol K² for SrCu₂As₂ (SrCu₂Sb₂). The complex optical dielectric function’s dispersion and the related optical properties such as refractive indices, extension coefficient, absorption coefficient, reflectivity, energy loss function, and optical conductivity were calculated and discussed in detail. The optical properties show a considerable anisotropy between the two components.     

Structural,optical, electrical properties of new hybrid organic–inorganic NLO single crystal: bis(1H-benzotriazole) hexaaqua-zinc bis(sulfate) tetrahydrate (BZS)

A new hybrid organic–inorganic nonlinear (NLO) single crystal, Bis(1H-benzotriazole) hexaaqua-zinc bis(sulfate) tetrahydrate (BZS), has been successfully synthesized and the single crystals were grown by slow evaporation solution growth technique (SESG) using Millipore water as a solvent. The structure of the BZS crystal was solved and refined by single-crystal X-ray diffraction and demonstrates that the grown crystals belong to a triclinic system with the space group P-1. The asymmetric part of the titled compound contains isolated organic cation (C₆H₆N₃)₂, metallic cation [Zn(H₂O)₆]²⁺, sulfate anion (SO₄)^2? and free H₂O molecules. The interplay between the wide number of intermolecular interaction such as O–H···O, N–H···O, C–H···O and π–π stacking interactions were discussed. The optical transmittance spectrum shows that the crystal is excellent transmittance in the entire Vis–NIR region with the cutoff wavelength at 345 nm. The presences of expected functional groups were identified by Fourier transform infrared spectroscopy. The dielectric measurements were carried out at different temperature in the frequency range 100 Hz–5MHz. Furthermore, the studies of its third-order NLO properties using a Z-scan technique demonstrate that the BZS crystal possesses a strong reverse saturable absorption (RSA) and the self-focusing (SF) nature with large second order hyperpolarizability (γ?=?6.24?×?10^?34 esu). All the results indicate that BZS crystal might be the potential candidate for the third-order NLO applications.     

Structural, photoluminescence and optical properties of chemically deposited (Cd1−xBix)S thin films as a function of dopant concentration

In this study, (Cd_1?xBi_x)S thin films were successfully deposited on suitably cleaned glass substrate at 60 °C temperature, using the chemical bath deposition technique. After deposition, the films were also annealed at 400 °C for 2 min in air. The structural properties of the deposited films were characterized using X-ray diffraction and AFM. Formation of cubic structure with preferential orientation along the (111) plane was confirmed together with BiS second phase from structural analysis. The interplanar spacing, lattice constant, and crystallite size of (Cd_1?xBi_x)S thin films were calculated by the XRD. The crystallite size of the un-doped CdS thin films was found to be 7.84 nm, which increased to 11.1 nm with increasing Bi content from 0 to 10 %. The surface roughness of the films was measured by AFM studies. The photoluminescence spectra were observed at red shifted band edge peak with increasing doping concentration of Bi from 0 to 5 % in the un-doped CdS thin films. The optical properties of the films are estimated using optical absorption and transmission spectra in the range of 400–800 nm using UV–VIS spectrophotometer. The optical band gap energy of the films was found to be decreased from 2.44 to 2.23 eV with the Bi content being from 0 to 5 %. After annealing, the band gap of these films further decreased.     

Structural and optical properties of Cd x Zn(1 − x)Te thin films

Seven Cd _x Zn_{(1 ? x} Te solid solutions with x = 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 were synthesized by fusing stoichiometric amounts of CdTe and ZnTe constituents in silica tubes. Each composition was used in the preparation of a group of thin films of different thicknesses. Structural investigation of the obtained films indicates they have a polycrystalline structure with predominant diffraction lines corresponding to (111) (220) and (311) reflecting planes, which can be attributed to the characteristics of growth with the (111) plane. The optical constants (the refractive index n, the absorption index k, and the absorption coefficient α) of Cd _x Zn_{(1 \s -x)} Te thin films were determined in the spectral range 500–2000 nm. At certain wavelengths it was found that the refractive index, n, increases with increasing molar fraction, x. It was also found that plots of α² (hv) and α^1/2 (hv) yield straight lines, corresponding to direct and indirect allowed transitions respectively obeying the following two equations: $$\begin{gathered} E_g^d = 1.583 + 0.277x + 0.197x^2 \hfill \\ E_g^{ind} = 1.281 + 0.111x + 0.302x^2 \hfill \\ \end{gathered}$$      

Photoluminescence and thermal properties of a red-emitting LnNbO4:Pr3+ (Ln = La,Gd, and Y) phosphor for warm WLEDs

Journal of Materials Science: Materials in Electronics - Efficiently red-emitting Pr3+-doped LnNbO4 (Ln?=?La, Gd, and Y) phosphors have been successfully prepared by the traditional...