Electrical Activation Energy Research Articles

Multi-scale structural regulation of negative temperature coefficient effect and electrical conduction mechanism of xSm2O3-(1-x) CaCu3Ti4O12 ceramics

In this work, a series of xSm2O3-(1-x) CaCu3Ti4O12 (xSm2O3-(1-x)CCTO, x = 0.00-0.05) negative temperature coefficient (NTC) ceramics were prepared by a solid-state method. The influence of Sm2O3 content on electrical properties was examined using microstructural, band gap, morphological, Direct Current (DC) resistivity, and impedance spectroscopy analysis. The increase in Sm2O3 content resulted in a gradual decrease of the resistivities (ρ25), thermal constants (B25/75), activation energies for electrical conduction (Ea) and activation energies of the relaxation process (Erelax) from 1.16×107 Ω•cm, 6387 K, 0.5456 eV and 0.5592 eV to 3.43×105 Ω•cm, 4149 K, 0.4088 eV and 0.4115 eV respectively. First-principles calculations revealed a reduction in the band gap by adding Sm2O3, partially explaining the decrease in electrical resistivity. In-situ XPS analysis elucidated a relationship between conduction mechanism of Sm2O3-doped CCTO ceramics and electron hopping. Impedance analyses showed that both grains and grain boundaries contributed to the NTC effect of ceramics. The electrical inhomogeneity arose from grains and grain boundaries, while local relaxation was due to the short-range motion of charge carriers.

Sonochemical synthesis of mesoporous ZnyCd1-yS quantum dots: Composition-dependent optical, electrical, dielectric, and hydrogen-generation characteristics

Mesoporous ZnyCd1-yS quantum dots (QDs) with mixed cubic–hexagonal phases prepared by sonochemical technique at varying Zn content. Incorporating Zn ions in the CdS lattice reduced the crystalline size and enhanced the corresponding surface areas at increasing Zn contents. The increase of Zn content in ZnyCd1-yS QDs increased the bandgap from 2.52 eV to 3.83 eV and enhanced the corresponding Urbach energy from 72 meV to 279 meV. ZnyCd1-yS QDs exhibited small electrical activation energies ranging from 249 mV to 361 mV. The effect of Zn content on the catalytic activity of ZnyCd1-yS QDs toward hydrogen production through NaBH4 hydrolysis was investigated at different temperatures. Ternary alloys ZnCdS QDs exhibited higher catalytic activity than pure ZnS and CdS QDs, with Zn0.5Cd0.5S QDs displaying the highest hydrogen generation rate of 96 mL∙min−1∙g−1. The increase of reaction temperature from 30°C to 60°C enhanced the rate constant of hydrogen production from 0.071 to 0.36 min−1. Based on the pseudo-first-order equation, the estimated apparent activation energy of Zn0.5Cd0.5S QDs was 45.3 kJ∙mol−1. Overall, the obtained results underscored the potential of ZnyCd1-yS QDs as promising catalysts for hydrogen generation.

NiCr2−xGdxO4 ceramics’ magnetic, structural and electrical conductivity as well as their activation energy properties

The goal of this work is to synthesize and characterize nanoscale nickel chromites nanoparticles doped with Gd using the economical solution combustion method. Numerous analytical techniques, including energy formation, electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction, are used for in-depth characterization. The results show that at low values of coercivity, high values of saturation magnetization, and low values of remnant magnetization, the chromites correspond. The crystalline size of Gd-doped nickel chromites decreases. For the normal spinel structure’s tetrahedral and octahedral coordinated forms, respectively. The present research shows that agglomerated forms and irregular, spherical structures formed by SEM (Scanning Electron Microscope) form regular structures. The present investigation uses a transmission electron microscope (TEM) to illustrate the formation of regular-shaped particles. As demonstrated by Gd-doped NiCr2O4 and pure NiCr2O4, stable interstitial positions are among the typical interstitial positions of the metal oxides. Investigations of magnetic properties from the paramagnetic to the ferromagnetic phase formation. Electrical conductivity and activation energy dropped with Gd doping of nickel chromites and showed an inverse relationship with particle/crystallite sizes. Lastly, applications for NiCr2−x GdxO4 particles were examined and future research directions were also suggested.

Manganese dioxide nanoparticles and nanocomposites with carbon black. Synthesis, physical-chemical and electrical properties

In this study, α- and β-MnO2 and composites with carbon black (CB) were chemically synthesized and prepared through mechanical mixing respectively. The samples’ crystal structure, morphology, and electrical properties have been investigated herein. It is found that average particle sizes of 12–15 nm and 18–24 nm for α- and β-MnO2, respectively. The surface area and average pore volume of obtained samples of α- and β-MnO2 are 200 and 70 m2/g, and 3.2 and 5.3 nm, respectively. The electrical conductivity performances and activation energy behavior of samples have been analyzed. The correlation between the CB content in the composites and their electrical conductivity was established based on experimental data. The electrical conductivity of the α-MnO2/C monotonic increase from 1.31 to 18.6 S/m. There was a 7.5-fold increase of conductivity for α-MnO2 with 15 wt.% CB and almost a 30-fold increase for β-MnO2 with the corresponding CB content compared to the pure samples. In composite samples, the activation energy decreases from 0.069 to 0.041 eV and from 0.154 to 0.074 eV for α- and β- MnO2/C, respectively.

Pulsed electric field processing of fruit juices with inactivation of enzymes with new inactivation kinetic model and determination of changes in quality parameters

Pulsed electric fields (PEF) processing of fresh grape, orange and tomato juices by 17.2–24.1 kV/cm electric field strengths, 130.0–1040.5 μs treatment times and 1.43–29.13 J/kg energies with respect to determination of the changes in the physical and bioactive properties, color parameters in addition to inactivation of pectin methyl esterase (PME), polyphenol oxidase (PPO), and lipoxygenase (LOX) enzymes were studied. In general, decrease in pH, increase in conductivity (except for grape juice), total phenolic substance content, and total antioxidant capacity with no significant change (p > 0.05) in total soluble solids were observed by PEF treatment for all juices. Except for hue value for orange juice, no significant changes (p > 0.05) were observed in color values. Inactivation of the enzymes were increased with increased energy, and calculated electrical activation energies for PME, PPO, and LOX enzymes were 8.31, 7.06, and 4.31 kJ/mol, respectively. Industrial relevanceEnzymes in addition microorganisms causing quality degradation is of great concern in fruit juice industry as most of the enzymes are resistant to processing technologies. Increased PEF treatment time provided over 95% inactivation on PME, PPO, and LOX enzymes with no adverse effect on quality properties of grape, orange, and tomato juices revealing a viable alternative to juice processing industry.

Electrical properties of epoxy/graphite flakes microcomposite at the percolation threshold concentration

The electrical properties and activation energy of epoxy/graphite flakes (GFs) micro-composite with different content of GFs (0.0625–1 wt%) were studied for electrical properties using Novocontrol Alpha Analyser (10−2 Hz—107 Hz). GFs sizes ranged from (100 nm to 10 μm). The analysis was performed by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), visible spectrum reflectance spectra (VIS) spectra, and Fourier Transform Infrared spectra (FTIR) spectroscopy. Increasing GFs content caused multiple changes in electrical characteristics. At 0.0625 wt%, all electrical properties noticeably increased. But at 0.125 to 0.25 wt%, immobilized nanolayers were formed leading to decreased permittivity, dielectric loss (tan(δ)), quality factor (Q-factor), capacitance, conductivity, and figure of merit (F-factor). At 0.25 wt%, the epoxy microcomposite had lower permittivity, tan(δ), conductivity, and capacitance compared with unfilled epoxy. With 0.5 wt% of GFs, signified the percolation threshold, initiating a rise in permittivity, conductivity, capacitance, and tan(δ), accompanied by the closer proximity of grain boundaries, facilitating the formation of conductive channels. At a concentration of 1 wt% of GFs, the establishment of continuous interfacial conductive pathways resulted in a remarkable augmentation of all dielectric properties. The Cole-Cole analysis has been employed to investigate variations in epoxy/GFs microcomposites based on concentration levels.

Analysis of a Flexible Photoconductor, Manufactured with Organic Semiconductor Films.

This work presents the evaluation of the electrical behavior of a flexible photoconductor with a planar heterojunction architecture made up of organic semiconductor films deposited by high vacuum evaporation. The heterojunction was characterized in its morphology and mechanical properties by scanning electron microscopy and atomic force microscopy. The electrical characterization was carried out through the approximations of ohmic and SCLC (Space-Charge Limited Current) behaviors using experimental J-V (current density-voltage) curves at different voltages and under different light conditions. The optimization of the photoconductor was carried out through annealing and accelerated lighting processes. With these treatments, the Knoop Hardness of the flexible photoconductor has reached a value of 8 with a tensile strength of 5.7 MPa. The ohmic and SCLC approximations demonstrate that the unannealed device has an ohmic behavior, whereas the annealed device has an SCLC behavior, and after the optimization process, an ohmic behavior and a maximum current density of 0.34 mA/mm2 were obtained under blue light. The approximations of the device's electron mobility (μn) and free carrier density (n0) were performed under different light conditions, and the electrical activation energy and electrical gap were obtained for the flexible organic device, resulting in appropriate properties for these applications.

Synergistic effect of Ag2WO4 interconnected nanoclusters for enhanced photovoltaic performance

Tungsten oxide nanoparticles (PW NPs) and silver-doped tungsten oxide nanocomposites (SW NCs) were synthesized via hydrothermal method. Structural, optical, morphological, and electrical properties of the synthesized samples were characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), and UV–visible spectroscopy. XRD results confirmed the formation of Ag2WO4 NCs with an average crystallite size ranging from 38 to 9 nm. SEM analysis revealed the formation of nanoclusters. Further SW4NCs shows highest rate constant (0.108 min−1) for methyl blue (MB) dye degradation. Variation in the electrical conductivity and activation energy was studied by DC conductivity studies. Dye-sensitized solar cells (DSSCs) were fabricated using PW and SW NCs films as photoanodes simultaneously, and the photoconversion efficiency (PCE) was found to increase.

Non-isothermal crystallization kinetics and memory switching properties of Tl-Se-Ge-Sb chalcogenide semiconductor alloy for thermally stable phase change memory applications

Quaternary (Tl20Se70Ge10)0.85Sb0.15 chalcogenide glass was synthesized using melt-quenching and thermal evaporation techniques for bulk and thin film samples, and its amorphous character was confirmed by XRD. Based on different models of non-isothermal crystallization kinetics, the average values of the glass transition and the crystallization activation energies are 121.33 and 82.94 kJ mol−1, respectively. The crystallization mechanism in the examined composition is 2D nucleation growth, according to Avrami exponent Thermal parameters of the studied quaternary glass, like fragility fluctuation free volume reduced glass transition temperature thermal stability and glass formation ability were investigated and indicated that the (Tl20Se70Ge10)0.85Sb0.15 ChG exhibits a good ability of glass formation and thermal stability. The obtained results of the dc electrical conductivity are found to increase with temperature and decrease with film thickness. The electrical conduction activation energy (0.583 ± 0.004 eV) is thickness independent and the predominant conduction mechanism is the hopping of charge carriers in the band tail localized states. The () curves of (Tl20Se70Ge10)0.85Sb0.15 chalcogenide glass film samples were analyzed and shown to be appropriate for a memory switch. The mean value of the threshold voltage decreases exponentially as temperature increases, whereas it increases linearly as film thickness increases. The values of threshold voltage and threshold resistance activation energies are 0.282 ± 0.003 and 0.521 ± 0.004 eV, respectively. The obtained switching characteristics data were discussed in view of the electrothermal model motivated by current channel Joule heating. These findings highlight the suitability of the investigated composition for various optoelectronic applications, such as memory switching devices, optical data storage, phase-change memories and optical fibres sensing devices.

Structural, micro-structural, morphological, electrical spectroscopy and optical analysis of lithium-titanium oxide electronic material

In this paper, we perform a thorough analysis into the electrical properties of high-purity, thick Li2TiO3 discs generated by the mixed oxide process, covering a wide range of frequencies and temperatures. Li2TiO3 samples are calcined and sintered at 920 °C and 940 °C. X-ray diffraction shows a monoclinic crystal structure with a space group of C2/c(15), matching JCPDS card (00-033-0831). The Scherrer and W-H plot methods provide consistent crystallite sizes of 51.23 and 49.34 nm. SEM and EDAX at room temperature reveal the material's structure and chemistry. The microstructure has well-defined porosity and homogeneous grain dispersion, with an average grain size of 2.82 µm. We studied frequencies from 1 kHz to 1 MHz and temperatures from 30 °C to 450 °C. Measure dielectric constant, tangent loss, and electrical conductivity. Above 350 °C, the dielectric constant increases significantly. Between 400 °C and 450 °C, electrical conductivity activation energy ranges from 0.431 to 0.624 eV. UV–Visible spectroscopy shows maximal absorption at 201 nm, indicating a band gap value of 3.78 eV. Its residual, saturation, and coercivity values were 0.00286 µc/cm2, 0.0267 µc/cm2, and 0.974 kV/cm, respectively, from the hysteresis loop. The UV spectrum shows Li2TiO3 absorbs most light at 201 nm and has a 3.82 eV band gap. Its composition and chemical processes are confirmed by FTIR peaks at various wavenumbers. Based on these results Li2TiO3 might have the potential applications in electronic devices such as capacitors, insulators, and electrochemical sensors as well as humidity and gas monitoring devices.

Experimental investigation of the bonding of sulfur in highly reduced silicate glasses and melts

Elucidating the role of sulfur on the structure of silicate glasses and melts at elevated pressures and temperatures is important for understanding transport properties, such as electrical conductivity and viscosity, of magma oceans and mantle-derived melts. These properties are fundamental for modeling the evolution of terrestrial planets and moons. Despite several investigations of sulfur speciation in glasses, questions remain regarding the effect of S on complex glasses at highly reducing conditions relevant to Mercury. Glasses were synthetized with compositions representative of the Northern Volcanic Plains of Mercury and containing quantities of S up to 5 wt%. Multiple spectroscopic methods and microprobe analyses were employed to probe the glasses, including in situ impedance spectroscopy at 2- and 4-GPa pressures and temperatures up to 1740 K using a multi-anvil press, 29Si NMR spectroscopy, and Raman spectroscopy. Electrical activation energies (Ea) in the glassy state range from 0.56 to 1.10 eV, in agreement with sodium as the main charge carrier. The electrical measurements indicate that sulfide improves Na+ transport and may overcome a known impeding effect of the divalent cation Ca2+. The glass transition temperature lies between 700 and 750 K, and for temperatures up to 970 K Ea decreases (0.35–0.68 eV) and the conductivities of the samples converge (∼5–8 × 10−3 S/m). At Tquench, the melt fraction is 50–70% and melt conductivity varies from 0.7 to 2.2 S/m, with the sample containing 5 wt% S the most conductive among the set. 29Si NMR spectra reveal that a high fraction of S bonds with Si in these complex glasses, a characteristic that has not been recognized previously. Raman spectra and maps reveal regions rich in Ca–S or Mg–S bonds. The evidence of sulfide interactions with both Si and Ca/Mg suggest that alkaline earth sulfides can be considered weak network modifiers in these glasses, under highly reduced conditions.

Electrical performance and conductive mechanism of xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 ceramics with NTC effect via chemical modification

xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 (xLCO-(1-x)BCTS) ceramics were manufactured using a solid-phase reaction method. All samples exhibited single cubic perovskite structures and a typical negative temperature coefficient (NTC) effect. The grain sizes increased with increasing LCO doping content. For all samples, the resistivities (ρ25), activation energies for electrical conduction (Ea), thermal constants (B25/75), and activation energies of the relaxation process (Erelax) were in the ranges of 5.93 × 104-9.36 × 108 Ω•cm, 0.3700–0.2951 eV, 3177–3988 K, and 0.3539–0.2890 eV, respectively. Such a combination of ρ and B renders these materials to be potential candidates for NTC thermistors. According to the XPS spectra and due to the difference in ion radius among Co3+, Co4+, Ti3+, and Ti4+, Co3+-O-Co2+ and Ti3+-O-Ti4+ bonds were formed, and the electrons in the continuous bonds generated jumping conduction. The fitted results of the equivalent circuit showed that Rg and Rgb decreased with increasing LCO content, which is consistent with the DC resistivity at 25 °C. The results of the analysis indicate that the conductive mechanism of xLCO-(1-x)BCTS ceramics was electron hopping conduction.

Structural, dielectric, electric and magnetic properties of magnesium substituted lithium nanoferrites

Magnesium substituted Li-ferrites nanoparticles with chemical composition Li0.5-0.5xMgxFe2.5-0.5xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1) synthesized by sol-gel auto combustion method. Synthesized materials were sintered at 600 °C for 4 h in the air and heated samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDS) techniques. Rietveld refinement of XRD patterns confirmed the formation of the spinel structure where the lattice constant varied with the increase of Mg content. The crystallite size of magnesium-substituted lithium ferrites was calculated using Scherrer's equation and showed slight changes while the W-H plot shows more changes. The electrical conductivity and activation energy of Mg-substituted lithium ferrite were strongly affected by Mg content and by which they appear to confirm to semiconductor nature. The paramagnetic transition to ferrite was confirmed by the change in the Arrhenius plot, which showed a large variation between two regions that differ in the values of the activation energy, where the values of activation energies in the ferrite region were greater than those that appeared in the para region, as well as the variation between the activation energy values in the non-substituted lithium ferrite. The dielectric parameters such as the real part of the dielectric constant and loss tangent of the samples were analyzed in the range of 50 Hz to 5 MHz at room temperature, 100, 300, and 500 °C. Curie's temperature showed a decrease with the increase in Mg content. Hysteresis loops were measured using a vibrating sample magnetometer (VSM) where both the temperature and the applied magnetic field were changed. The FC result of Li0.5-0.5xMgxFe2.5-0.5xO4 (x = 0.2, 0.4, and 0.6) is almost flat below TB which demonstrates that the Li–Mg nano ferrites show a super-spin glass behaviour.

Bandgap narrowing and hole self-trapping reduction in Ga2O3 by Bi2O3 alloying

Ga2O3 is an emerging material with attractive electrical properties for improving the performance of high-voltage power electronics, and it is widely accepted that engineering its band edge energies will expand its applications, especially for bipolar devices. In this work, monoclinic phase (BixGa1−x)2O3 ternary alloys are fabricated on c-plane sapphire via magnetron co-sputtering of Ga2O3 and Bi2O3. The bandgap of Ga2O3 is found to decrease from 4.97 to 4.78 eV by alloying with a Bi x-fraction of 0.04, consistent with the theoretical prediction that alloying with Bi2O3 causes the up-shift of the valence band. Concurrent temperature-resolved cathodoluminescence (CL) measurements of the Ga2O3 and (Bi0.04Ga0.96)2O3 are employed to investigate their intrinsic ultraviolet (UV) luminescence and defect-related visible bands with increasing temperature from 80 K. The CL results reveal a more rapid thermal quenching of the self-trapped hole (STH) emission with an activation energy of only 32 meV, suggesting that alloying with Bi2O3 lowers the self-trapping energy for holes. Temperature-dependent electrical measurements reveal the conductivity of the (Bi0.04Ga0.96)2O3 film is one order of magnitude lower than that of the undoped Ga2O3 counterpart; however, both possess an electrical activation energy of ∼ 26 meV, likely associated with an impurity-related shallow donor. The low electrical conductivity of (Bi0.04Ga0.96)2O3 can be attributed to the compensation of shallow donors by acceptors activated by the Bi2O3-induced upward shift of the valence band edge. The frequency-dependent conduction and ionic polarization mechanisms up to 107 Hz are found to be identical for Ga2O3 and (Bi0.04Ga0.96)2O3, indicating that the conduction in this ternary alloy does not involve the activation of Bi acceptors.

Stability and Degradation in Lead Halide Perovskite Nanocrystals via Regulation of Lattice Strain.

It is still quite challenging to achieve high-performance and stable blue perovskite materials due to their instability and degradation. The lattice strain provides an important pathway to investigate the degradation process. In this article, the lattice strain in perovskite nanocrystals was regulated by the ratio of Cs+, EA+, and Rb+ cations with different sizes. Their electrical structure, formation energy, and ion migration activation energy were calculated with the density functional theory (DFT) method. The luminescence properties and stability of blue lead bromide perovskite nanocrystals were analyzed with spectra regulation from 516 to 472 nm. It was demonstrated that the lattice strain plays an important role in the luminescence performance and degradation process of perovskite materials. The study provides the positive correlation between lattice strain and degradation as well as luminescence properties in lead halide perovskite materials, which is of great importance in uncovering their degradation mechanism and developing stable and high-performance blue perovskite materials.

Structure and Electrical Conductivity of Bismuth- and Germanium-Doped Calcium Molybdates

Ca1 – 2xBi2xMo1 – xGexO4 solid solutions with a scheelite-like structure (space group I41/a) and the homogeneity range х = 0.0–0.4 were prepared using standard ceramic technology. The unit cell parameter с and unit cell volume increase as the dopant concentration increases due to the changing size of Ca/BiO8 polyhedra. The predominant thermal expansion of Ca/BiO8 polyhedra was inferred from the temperature-dependent unit cell parameters and Raman spectral patterns. The Ca/Bi–O and Mo/Ge–O bond lengths were calculated. The increasing dopant concentration decreases the thermal expansion coefficient of the ceramics and increases the electrical conductivity and activation energy of the complex oxides compared to the matrix compound. The effective oxygen diffusion coefficient is determined.

Synthesis and characterization of N,N′-Di-1-naphthyl-N,N′-diphenylbenzidine as a hole-transporting layer (HTL) for Perovskite solar cell applications

In this communication, we report a typical structural, optical and electrical analysis of thin films of hole transport material (HTM) based on aromatic phenyl benzidine derivative (N,N[Formula: see text]-Di-1-naphthyl-N,N[Formula: see text]-diphenylbenzidine) deposited by thermal evaporation technique onto the glass substrate. The effect of substrate temperature on the physical and electronic properties of these organic thin films for perovskite solar cells (PSCs) applications has been investigated. The films have been characterized by FTIR, XRD, SEM, UV–Vis spectroscopy and photoluminescence spectroscopy. Electrical conductivity and activation energies of films have also been calculated. From FTIR data of fabricated films and powder, it was found that the compound does not decompose during the thermal evaporation process as observed vibrational frequencies of films and the powder are the same. From the results, it has been determined that the substrate temperature has a huge impact on the physical structure and has also influenced the optical, electrical properties of the films. As observed from the studies it appears that these amorphous films with bandgap near to 3[Formula: see text]eV and suitable conductivity have potential for photovoltaics layer devices. From this study, it can be concluded that N,N[Formula: see text]-Di-1-naphthyl-N,N[Formula: see text]-diphenylbenzidine can be used as an active hole transport layer in PSCs.

Influence of the Coordinated Ligand on the Optical and Electrical Properties in Titanium Phthalocyanine-Based Active Films for Photovoltaics.

Tetravalent titanyl phthalocyanine (TiOPc) and titanium phthalocyanine dichloride (TiCl2Pc) films were deposited via the high-vacuum thermal evaporation technique and subsequently structurally and morphologically characterized, to be later evaluated in terms of their optoelectronic behavior. The IR and UV-vis spectroscopy of the films displayed α- and β-phase signals in TiOPc and TiCl2Pc. Additionally, the UV-vis spectra displayed the B and Q bands in the near-UV region of 270-390 nm and in the visible region between 600 and 880 nm, respectively. The films presented the onset gap (~1.30 eV) and the optical gap (~2.85 eV). Photoluminescence emission bands at 400-600 nm and 800-950 nm are present for the films. One-layer ITO/TiCl2Pc or TiOPc/Ag and two-layer ITO/PEDOT:PSS/TiCl2Pc or TiOPc/Ag planar heterojunction devices with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) deposited by the spin-coating technique were constructed. In these devices, an electrical activation energy between 0.18 and 0.21 eV and a refractive index between 1.14 and 1.44 were obtained. The devices presented a change in the J-V curves for the illuminated and darkness conditions, as much as 1.5 × 102 A/cm2, related to the device architecture and phthalocyanine ligand. The latter indicates that the films should be used for optoelectronic applications.

Valence Engineering Enhancing NH4 + Storage Capacity of Manganese Oxides.

Ammonium ions (NH4 + ), as non-metallic charge carriers, are attracting attention in aqueous batteries due to its low molar mass, element sufficiency, and non-toxicity. However, the host materials for NH4 + storage are still limited. Herein, an oxygen defects-rich manganese oxide (MnO2-x ) for NH4 + storage are reported. The oxygen defects can endow the MnO2-x sample with improved electric conductivity and low interface activation energy. The electrochemical reaction mechanism is also verified by using ex situ X-ray photoelectron spectroscopy (XPS) and fourier transform infrared spectroscopy (FT-IR), demonstrating the insertion and extraction of NH4 + in the MnO2-x by formation/breaking of a hydrogen bond. As a result, MnO2-x delivers a high capacity of 109.9mAhg-1 at the current density of 0.5Ag-1 and retention of 24mAhg-1 after 1000 cycles at the current density of 4Ag-1 , outperforming the pristine MnO2 sample.

Structural, Swanepoel’s method, optical and electrical parameters of vacuum evaporated Zn50Se50 thin films

Thin films of Zn50Se50 were prepared by the vacuum evaporation technique on glass substrates. The influence of annealing temperature (Tann.) on the structural and optical properties of ZnSe polycrystalline films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical transmittance T (λ). The crystalline phases that were found in the Zn50Se50 thin films are ZnSe, Se and Zn. The refractive index (n) and the thickness of the films (d) were calculated using Swanepoel’s method for the films annealed at (423 K). The mechanism of optical absorption follows the rule of direct transition. The values of band gap (EG) were found to decrease from about 2.933 to 2.635 eV with the increasin of the Tann. from 300 to 423 K. Urbach energy (EU) was calculated and found to the increase by increasing Tann. The dispersion of the n was discussed in terms of the single-oscillator Wemple and DiDomenico model. The Arrhenius formula was used to discuss the electrical conductivity (σDC), activation energy (ΔE) and preexponential factor (σo).