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A ternary oxide nanocomposite based on Bi2O3/MgO/GO was prepared using a co-precipitation method taking into consideration of preparing the material for photoconductive device applications.

A novel and astonishing p-GeSe/n-HfS2 NDR device shows a high value for the peak-to-valley current ratio in the range of 5.8.

In light of existing literature of stable ferromagnetic phase, the thermoelectric and optical behavior of the Cd-based spinel chalcogenides i.e. CdCr2X4, (X = S, Se, Te) were inspected and their structural and electronic characteristics were examined in terms of density functional theory calculations. The negative values of formation energy of said spinels were calculated to confirm their ferromagnetic phase stability. Optimization of band structure and calculations of density of states confirmed their ferromagnetic nature. For both channel, the band structure exhibited the semiconducting behavior. The exchange constants (N0α and N0β) were investigated with the help of exchange splitting energies, which were explored from the density of states. The splitting of 3d-states of Cr were explained on the basis of larger value of N0β as compared with N0α. Owing to the strong p-d hybridization indicated by N0β = −0.11, −0.12 and −0.15 and N0α = 0.14, 0.32 and 0.44 for CdCr2S4, CdCr2Se4 and CdCr2Te4, respectively, the necessary condition for ferromagnetic system is satisfied showing that exchange field dominates over the crystal field that induces the ferromagnetism in these spinels. Moreover the p-d hybridization was used to decrease the magnetic moment at Cr ions, by using a fraction of magnetic moment at non-magnetic sites. Further, optical characteristics were investigated in terms of photon energy 0–6 eV showing less dispersion of light and refractive index ranges up to 1–1.5 in visible region, thus suggesting spinels as potential candidates for opto-electronic applications. The thermoelectric performance observed in the temperature range of 200–600K which indicate positive Seebeck coefficients of ∼250 CdCr2S4, CdCr2Se4 while a negative Seebeck coefficients of −112 for CdCr2Te4 at room temperature. Further the power factors increased from S to Te as well as with increase of temperature which shows the potential of these chalcogens for thermoelectric power generators.

Nanoparticles of nickel-doped iron chromite (Fe1-xNixCr2O4) with composition x = 0.2-0.8 have been prepared by the sol–gel method using citric acid as a complexing agent. X-ray diffraction (XRD) re...

Metal Organic framework (MOFs) a diverse class of complex organic metal assemblages has been attracting a great interest due to its easy tunability and modified characteristics during the past few years. These nanoscale-to-microscale-sized structures have been employed in different applicative fields due to their striking functional chemistry. Barium MOF synthesis is based on barium metal ions tri-linked organically to form a cubic structure and features photolumincity. Ba-MOF was synthesized by hydrothermal method and structural and optical analysis was performed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Raman Spectroscopy and Zeta Potential. The presence of cubic structure and organic carbon and oxygen linkages was indicated by XRD peaks. EDS directs the presence of barium as well as carbon and oxygen (organic linkers). Raman analysis paid for witnessing the evidence of the synthesis of MOF structure by validating the peak location. The photoluminescence spectrum was applied to measure the bandwidth to study the photoluminescence characteristics. The PL spectrum presented a wide bandwidth of 107.4 nm indicating Ba-MOF to be an efficient photoluminescent nanocomposite for photoluminescence-based applications. Zeta potential value of [Formula: see text] mV characterized anionic behavior and high stability of fabricated Ba-MOF.

Lead-free Perovskite materials have acquired a lot of interest owing to their potential to overcome the stability and toxicity concerns compared to traditional perovskite solar cells. Chalcogenide perovskites (ABX3, where A = Ba, B = Zr, X = S and/or Se) are emerging materials for photovoltaic (PV) applications. Computer-based designing of metal chalcogenide semiconductors, resulting in the identification of extremely appealing ABX3 substances and their derivatives that may be used as absorbers in thin-film PV devices. In this context, here the numerical studies are performed using the SCAPS-1D simulator for designing of chalcogenide perovskites-based solar cells. We used FTO (Fluorine-doped tin oxide), TiO2 as electron transport layer (ETL), BaZrS3, and BaZrSe3 as an absorber layer, Spiro-OMeTAD as a hole transport layer (HTL), and Au as a metal back contact. The simulations are conducted under AM 1.5G solar spectrum designed to maximise the efficiency of the proposed solar cell. The selection of the optimal parameters such as thickness, defect density and temperature for all the layers including absorber, FTO, ETM, and HTM is examined. The parameters are considered, keeping in mind their impact on solar cell performance, budget effectiveness, and the physics of the entire solar cell architecture. The effect of temperatures between 300 K to 450 K is studied. The results indicate that the power conversion efficiency (PCE), FF (fill factor), Voc (Open Circuit Voltage) and Jsc for BaZrS3 is 12.12%, 79.40%, 0.70 V, 22.00 mA cm−2, respectively, whereas for BaZrSe3 it is 25.84%, 77.32%, 0.72 V, 46.65 mA cm−2, respectively. This shows that BaZrSe3 has the potential to replace BaZrS3.

The gamma-ray and fast/thermal neutron shielding properties of bismo-borate glasses modified with Nd2O3 in the form B2O3–Bi2O3–SrO-Nd2O3 (BBSN0.0-BBSN5.7) were investigated. The newly developed Phy-X/PSD software and Geant4 simulation code were performed to achieve this goal by evaluating several parameters such as MAC, gamma photons dose rate, FNRCS, and scattering/absorption lengths and cross sections for thermal neutrons. At low photon energy; 0.015 MeV, MAC values varied from 76.72, 76.57, 76.43, 76.29, 76.10, and 75.93 cm2 g−1 for BBSN0.0, BBSN1.0, BBSN2.0, BBSN3.0, BBSN4.3, and BBSN5.7, respectively. The HVL followed reversible trend as follows; BBSN0.0 > BBSN1.0 > BBSN2.0 > BBSN3.0 > BBSN4.3 > BBSN5.7. The highest values for Zeff were found at low energy photon range (0.015 MeV) with the values of 76.71, 76.35, 76.00, 75.65, 75.21, and 74.75, while the lowest values were found at 1.5 MeV; 21.32, 21.42, 21.52, 21.61, 21.73, and 21.87 for BBSN0.0 – BBSN5.7, respectively. The gamma dose rate has a dramatic decrease with increasing the glass thickness from 1 mm to 5 mm. Furthermore, glasses with the highest concentration of Nd2O3 show the best thermal/fast neutron shielding capability among the investigated glasses. One can conclude that BBSN5.7 glass owns the best shielding capacity among all BBSN glasses due to the highest LAC values comparing to other selected ones.

Semiconducting glassy chalcogenides (ChGs) have broad technological applications owing to the ability to tune their band gap through composition change. However, there is a lack of theoretical mode...

International audience; Hydrophobic elastomers are capable of absorbing a small amount of water that forms droplets around hydrophilic sites. These systems allow the study of confinement effects by a hydrophobic environment on the dynamics and thermodynamic behaviour of water molecules. The freezing–melting properties and the dynamics of water inside nano-droplets in butyl rubber are affected, as revealed by differential scanning calorimetry (DSC) and deuterium nuclear magnetic resonance (2H-NMR). Upon cooling down, all water crystalizes with a bimodal droplet population (da = 3.4 nm and db = 4.4 nm) in a temperature range associated with the droplet size distribution. However, the melting temperature is not shifted according to the Gibbs–Thomson equation. The relative decrease of the 2H-NMR longitudinal magnetization is not a single exponential and, by inverse Laplace transformation, it was deduced to be bimodal in agreement with the DSC measurements (T1,a ∼ 10 ms and T1,b ∼ 200 ms). The deduced correlation time of molecular reorientation is longer than that of bulk water and the behaviour with temperature follows the Vogel-Fulcher-Tammann (VFT) equations with a changing fragility as the droplet size is reduced when reducing hydration.

In this work, the electrical, and optical properties are investigated for MgSc2Te4 and MgY2Te4 spinel compounds under the effect of pressure up to 15 and 30 GPa, respectively. These compounds are suitable for optoelectronics and photovoltaic applications. Trans-Blaha modified Becke Johnson (TB-mBJ) approximation exchange and correlation functionals were used to uncover electronic and optical properties. The electronic band gaps of both compounds appear to be direct despite the effect of pressure. MgSc2Te4 exhibits metallic behavior at 15 GPa, while MgY2Te4 exhibits metallic behavior at 30 GPa. Density of states spectra used to identify the atomic contribution of states by ions in the bands. Real part of the dielectric function, optical reflectivity and refractive index upshifted with the increase in energy while the imaginary parts of the dielectric function, optical conductivity and absorption coefficient red-shifted with the increase of hydrostatic pressure.

This article focuses on the physical properties of MgFe2Z4 (Z = S, Se) spinels investigated by employing density functional theory calculations. To explore the magnetic and electronic properties, WIEN2k code was executed whereas thermoelectric properties were studied using the BoltzTraP. The determined negative formation energies and positive phonon frequencies show that the system under investigation is stable. The lowest possible ground state energies clearly indicate that spinels lie in ferromagnetic state. Studied spinels illustrated half-metallic nature upon employing the calculations of density of states (DOS) and spin-polarized band structures (BS). Ferromagnetic (FM) state was found to be stable ground state. Observation of ferromagnetism in these compounds was ensured by exchange energies, Jahn-Teller energy and hybridization and is attributed to electron spin in place of Fe2+ clustering. Curie temperature and spin polarization of these compounds is also comprehensively investigated in this study. Analysis of the thermoelectric properties showed a good fit between the ratio of electrical (σ/τ) and thermal conductivity (κ e/τ). Thermoelectric efficiency of studied compounds is found to be appropriate as demonstrated by the thermoelectric power factors.

For the fabrication of thermoelectric and optoelectronic devices, metal halide perovskite materials are perfect applicants. In this work, first-principles computation is carried out to explore the structural, optical, electronic, and transport features of Rb2InGaX6(X = Cl, Br, I).In structural calculations, the obtained value of Paugh’s ratio(B/G) reveals the material’s brittleness. The acquired negative value of enthalpy of formation (∆Hf) exposes the studied materials are stable. The exploitation of band structure exhibits that the Rb2InGaX6(X = Cl, Br) compound possesses an indirect bandgap value of 2.20eV for Cl, which significantly decreases to 0.90 eV by substituting anion from Cl up to I. The materials under observation possess a remarkable absorption coefficient α (ω) in ultraviolet and visible region (2–8eV) of light spectra, which makes it practical for photocell and optical device fabrication. Furthermore, the transport features are estimated by utilizing the BoltzTrap code within the temperature range of 200–500 K. The calculated value of the figure of merit (ZT) indicates that Rb2GaInX6 (X = Cl, Br, I) compounds are a potential candidate for thermoelectric device applications.

Transition metal dichalcogenides (TMDs) have received significant attention owing to their thickness-dependent folded current-voltage (

The electric conductivity and thermoelectric power for different compositions of the chalcogenide glasses (SbSn)xSe100−x (x = 4, 8, 12, 16 and 20 at.%) were measured experimentally. The dc conductivity is found to have an Arrhenius behavior in the temperature range (300–450) K with typical activation energies decreasing from 0.87 to 0.74 eV with the SbSn content. The concentrations of charge carriers, as well as their mobility and characteristic relaxation time were deduced in the same temperature range and compositions. The variations of activation energy calculated from measured electric conductivity versus SbSn content are compared to the behavior of calculated half band gap. From the measured Seebeck coefficient, we deduced its specific activation energy and found that it is lower than that related to electric conductivity. This difference is assumed to be the activation energy needed for polaron hopping. The increase in cross-linking with SbSn content is proposed as an explanation for the increase in polaron-hopping activation energy.

The structural, electronic, optical, elastic, and thermoelectric (TE) characteristics of Na2YCuX6 (X = Br, Cl) halide double-perovskites (HDPs) were investigated by using first principle approach within WIEN2K code. Perdew, Burke and Ernzerhof generalized-gradient approximation (PBEsol-GGA) with modified Becke-Johnson (mBJ) potential were used in the current investigations. Enthalpy of formation energies (Ef) determined for Na2YCuBr6 and Na2YCuCl6 were −2.29 and −1.955 eV, correspondingly which verify the stability of both compounds. Na2YCuBr6 is discovered to be semiconducting with indirect bandgap (Eg) of 2.492 and Na2YCuCl6 has direct Eg of 2.571 eV. Absorption coefficient shows largest values at 5.74 and 6.92 eV for Na2YCuBr6 and Na2YCuCl6, correspondingly, which lie in UV range. Pugh’s ratio (B/G) values were calculated as 2.00 and 4.62 for Na2YCuCl6 and Na2YCuBr6, correspondingly which ensure the ionic bond and ductile characteristics of the compounds. From the TE calculations, ZT shows maximum values of 0.74 and 0.73 for Na2YCuBr6 and Na2YCuCl6, respectively. Results showed that investigated materials are efficient candidates for optoelectronic and TE appliances.

In this paper, the first principle investigations are performed to compute the electronic, optical, magnetic and thermoelectric (TE) features of Ba1−xMnxS (x = 6.25%, 12.5% and 25%) alloys by using density functional theory (DFT). The semiconductor behavior of pure BaS and half metallic ferromagnetic (HMF) nature of Ba1−xMnxS (x = 6.25%, 12.5% and 25%) is confirmed by investigating electronic band structure (EBS) with spin-resolved density of states (DOS). The MTot is mainly originated from Mn atom due to the presence of 3d-orbitals. In addition, the optical constants including refractive index, absorption and optical spectrum, reflectivity and dielectric function are analyzed in the span of 0–10 eV. It is found that the studied alloy operate within visible to ultraviolet (UV) energy range. Moreover, the TE properties such as figure of merit (ZT), power factor (PF), electrical and thermal conductivity are also calculated by using the BoltzTrap package. The high values of ZTof Ba1−xMnxS (x = 6.25%, 12.5% and 25%) qualify it for use in TE applications.The outcomes revealed the application of Ba1−xMnxS in spintronic and TE gadgets.

International audience; The freezing, melting and dynamics of supercooled water at different hydration of controlled porous glass (CPG) with mean pore sizes 10 nm, 30 nm, 50 nm and 70 nm are studied using differential scanning calorimetry (DSC) and deuteruim nuclear magnetic resonance (2 H-NMR). For saturated samples, the melting tempertaure follows the Gibbs-Thomson relation despite a clear linear decrease of the melting enthalpy when the transition is shifted due to confinement. For partially filled porous glasses the crystalization and melting temperatures as well as enthalpy are lower than for the saturated samples. 2 H-NMR confirms the existence of a non-crystallizable part of water adsorbed on the surface of pores. At room temperature, spin-lattice relaxation rate (1/T1) is proportional to the inverse of the mean pore size indicating that the relaxation is governed by a surface limited process. At low tempertaure relaxation rate follows the Vogel-Fulcher-Tammann (VFT) relation.

Effects of incorporating (SbS) in the quaternary (CdTe)100-x(SbS)x (x = 0, 8, 16, 20 and 28 at. %) glasses on different physico-chemical properties were investigated using the chemical bond approach. In addition to the estimation of the coordination number, constraint number (Ns), heat of atomization (Hs), cohesive energy and lone pair electrons, one presents theoretically the band gap estimation as well as the valence band (EVB) and conduction band (ECB) positions. The theoretical estimations of band gap are in good agreement with the previously published experimental results, and all compounds have their band gap in the infrared range (from 1.58 to 1.36 eV). Therefore, these materials may be used as an optical absorber in the wavelength range between 0.784 and 0.911 μm. This indicates that the studied compositions could be used for the development of new-generation infrared systems as well as for solar cell devices. Furthermore, the increase of (SbS) content decreases the network rigidity, but due to the decrease in the excess of Cd–Cd, one found, in contrary, an increase in the cohesive energy of the system.

Thin amorphous films of Ge5As22Te73–xInx (where x = 0, 3, 6 and 9 at. %) were thermally evaporated on glass substrates. The Seebeck coefficient (S) or simply thermoelectric power, dc electrical conductivity (σd), and photoconductivity (σph) were measured within the temperature (T) range 300–420 K on the prepared thin films. The activation energies for dark conduction (∆Ed), thermoelectric (∆ES) and photoconduction (∆Eph) were estimated using the values of σd, S, and σph, respectively. The current density (J) is found to be directly proportional to applied electric field (E) for the thin films indicating Ohmic behavior for E

Highly demanding efficiency, scaling and cost led the researchers to predict and synthesize two-dimensional transition metal dichalcogenides for advanced technology. Using the first-principles calculations, we study the optoelectronic properties, and device absorption efficiency of Janus SnSSe monolayer. The Janus SnSSe exist in two different phases, 1T and 2H structures. We find the 1T structure dynamically more stable than the 2H structure due lower energy and no-negative frequencies in the phonon spectra. The 1T SnSSe possess semiconductiing nature with an indirect bande-gap of 1.61 eV. The Janus SnSSe possesses a strong absorption having sharp absorption edges, showing the transition of electron to the conduction band from the valence band. We find that the Janus SnSSe strongly absorb light below 4.0 eV, which show its prominent applications for solar cell. A strong absorption from infra-red to the ultra-violet region of light spectrum make it promising in the optical devices. Furthermore, the wider band gap nature having strong device absorption-efficiency could make it suitable for the top cell in the tandem architecture.

Glass transition features of chalcogenides are important for the broad and increasing industrial applications of these glassy semiconductors. Hence, differential scanning calorimetry was applied at different scanning rates on As30Te64Ga6 prepared by conventional melt quenching technique in order to study their glass transition and fragility. The Kauzmann temperature was estimated to about 136 K while its glass transition is about 397 K at 10 K min−1. Different experimental evaluation methods gave the same fragility index m = 25 or D = 71 which is typical of a strong liquid corresponding to the prepared glass. Four iso-conversional methods were then applied to monitor the change in the activation energy for the temperature range corresponding to the transition from glass to liquid. All methods give a small monotonic decrease of the activation energy during transition from 108 to 99 kJ mol−1 confirming the strong character.

The structure and porosity of carbon black (CB) grades determine the ultimate applications of these most industrially used members of carbon materials. Hence, one uses complimentary methods to investigate these features for two conductive CB grades in order to understand their effects on the electric properties of polymeric nanocomposites. The mean particle size, the aggregate structure and voids morphology are studied by scanning electron microscopy (SEM) whereas high resolution transmission electron microscopy (HRTEM) reveals the ordering of the graphitic layers inside a CB particle as well as particles interconnections. The specific surface, voids size distribution and specific voids volume are studied using nitrogen adsorption, differential scanning calorimetry (DSC) thermoporosimety and nuclear magnetic resonance (NMR) relaxometry. This comparative study revealed a relatively smaller particle size, higher specific surface and specific volume with more disorder graphitic layers in Ketjenblack EC600JD than in Printex XE2. Finally, one presents the effect of such structural and porosity differences on the electric conductivity of nanocomposites made of these two grades.

The effects of the Aluminium concentration on the emission of Al 0.45 In 0.55 As/Al y Ga 1− y As quantum dots (QDs) are investigated by photoluminescence (PL), with the excitation power density as a variable parameter. The influence of a varying barrier composition on the QD emission is investigated theoretically and discussed with respect to PL measurements. For the highest barrier composition value ( y = 0.77), we interpret the QD emission as originating from indirect type-II transitions involving electrons in the barrier X valley and heavy holes (HH), with S and P symmetry, in Al 0.45 In 0.55 As QDs. The PL spectra of the y = 0.38 sample exhibits three lines: two of them are related to indirect type-II transitions, in which the electron ground state belongs to the indirect gap (L and X) minima in the barrier conduction band, whereas the third transition is attributed to a direct type-I transitions.

The effect of iodine content in Ix (As20Se80)100-x where x=0, 4, 8, 12, and 16 atomic % was studied both theoretically and experimentally. The calculated mean coordination number, cohesion energy, mean overall bonding energy, and band gap decrease with iodine content. This is correlated to the decrease of crosslinking by progressive incorporation of iodine. The impact of increasing iodine content on optical properties was studied through the analysis of a single reflection spectrum using Minkov's method. The experimentally evaluated band gap decreases from 1.7 eV to 1.41 eV in good agreement with the different estimations based on Manca's relation. The Urbach energy, related to the structural disorder, increases with the incorporation of iodine. From the measured refraction index, one deduces that the single oscillator energy decreases with iodine content while its dispersion energy increases. The nonlinear optical properties increase substantially with the incorporation of the more polarizable iodine atom.