Characterization of nano-crystalline LiNiVO4 synthesized by hydrothermal process

LiOH·H₂O, Ni(CH₃COO)₂·4H₂O and NH₄VO₃ were used to synthesize nano-crystalline LiNiVO₄ by hydrothermal process in deionized water at 150 °C for 2 h and subsequent calcination at 300-600 °C for 6 h. By using an X-ray diffractometer (XRD), a transmission electron microscope (TEM) and a selected area electron diffraction (SAED) method, nano-crystalline LiNiVO₄ with inverse spinel structure was detected. The stretching vibration of VO₄ tetrahedrons analyzed by a Fourier transform infrared spectrometer (FTIR) was split into three bands at 661, 746 and 835 cm^− 1, and that analyzed by a Raman spectrometer was detected at 823.9 and 787.7 cm^− 1. The thermogravimetric and differential thermal analyses (TGA and DTA) show two discrete weight losses at 25-117 °C and 117-600 °C and four endothermic peaks at 84, 145, 202 and 372 °C, corresponding to the evaporation of water and the decomposition of inorganic and organic compounds.     

Chemical deposition of Al2O3 thin films on Si substrates

Uniform Al₂O₃ films were deposited on silicon substrates by the sol–gel process from stable coating solutions. The technological procedure includes spin coating deposition and investigating the influence of the annealing temperature on the dielectric properties. The layers were studied by Fourier transform infrared spectroscopy and Scanning Electron Spectroscopy. The electrical measurements have been carried out on metal–insulator–semiconductor (MIS) structures. The C–V curves show a negative fixed charge at the interface and density of the interface state, Dit, 3.7 × 10¹¹ eV^− 1cm^− 2 for annealing temperature at 750 °C.     

Structural, electrochemical and optical comparisons of tungsten oxide coatings derived from tungsten powder-based sols

Tungsten trioxide (WO₃) electrochromic coatings have been formed on indium tin oxide-coated glass substrates by aqueous routes. Coating sols are obtained by dissolving tungsten powder in acetylated (APTA) or plain peroxotungstic acid (PTA) solutions. The structural evolution and electrochromic performance of the coatings as a function of calcination temperature (250 °C and 400 °C) have been reported. Differential scanning calorimetry and X-ray diffraction have shown that amorphous WO₃ films are formed after calcination at 250 °C for both processing routes; however, the coatings that calcined at 400 °C were crystalline in both cases. The calcination temperature-dependent crystallinity of the coatings results in differences in optical properties of the coatings. Higher coloration efficiencies can be achieved with amorphous coatings than could be seen in the crystalline coatings. The transmittance values (at 800 nm) in the colored state are 35% and 56% for 250 °C and 400 °C-calcined coatings, respectively. The electrochemical properties are more significantly influenced by the method of sol preparation. The ion storage capacities designating the electrochemical properties are found in the range of 1.62–2.74 × 10^− 3 (mC cm^− 2) for APTA coatings; and 0.35–1.62 × 10^− 3 (mC cm^− 2) for PTA coatings. As a result, a correlation between the microstructure and the electrochromic performance has been established.     

Electrical and optical properties of 12CaO·7Al2O3 electride doped indium tin oxide thin film deposited by RF magnetron co-sputtering

12CaO·7Al₂O₃ electride (C12A7:e⁻) doped indium tin oxide (ITO) (ITO:C12A7:e⁻) thin films were fabricated on a glass substrate by an RF magnetron co-sputtering system with increasing number of C12A7:e⁻ chips (from 1 to 7) and at various oxygen partial pressure ratios. The optical transmittance of the ITO:C12A7:e⁻ thin film was higher than 70% in the visible wavelength region. In the electrical properties of the thin film, a decrease of the carrier concentration from 2.6 × 10²⁰ cm^− 3 to 2.1 × 10¹⁸ cm^− 3 and increase of the resistivity from 1.4 × 10^− 3 Ω cm to 4.1 × 10^− 1 Ω cm were observed with increasing number of C12A7:e⁻ chips and oxygen partial pressure ratios. It was also observed that the Hall mobility was decreased from 17.27 cm²·V^− 1·s^− 1 to 5.13 cm²·V^− 1·s^− 1. The work function of the ITO thin film was reduced by doping it with C12A7:e⁻.     

New powellite type oxides in Ca–R–Nb–Mo–O system (R = Y, La, Nd, Sm or Bi)—Their synthesis, structure and dielectric properties

New complex oxides having powellite (CaMoO₄) type structure in the Ca–R–Nb–Mo–O system (R = Y, La, Nd, Sm or Bi) were prepared employing the method of solid state reaction between the component oxides at high temperature (1000–1100 °C). The new compounds, CaRNbMoO₈ (R = Y, La, Nd, Sm, Bi) are colorless and electrical insulators. The dielectric constants (K at 1 MHz) of these compounds are in the range 14–33 and K shows very little variation in the temperature range 30–100 °C. Their temperature coefficient of dielectric constant (TCK) is negative, which varies from − 21 to − 220 ppm/°C.     

Preparation of SrAl2O4: Eu, Dy nanometer phosphors by detonation method

SrAl₂O₄: Eu²⁺, Dy³⁺ nanometer phosphors were synthesized by detonation method. The particle morphology and optical properties of detonation soot that was heated at different temperatures (600–1100 °C) had been studied systematically by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results indicated SrAl₂O₄: Eu²⁺, Dy³⁺ nanometer powders in monoclinic system (a = 8.442, b = 8.822, c = 5.160, β = 93.415) can be synthesized by detonation method, when detonation soot was heated at 600–800 °C. The particle size of SrAl₂O₄: Eu²⁺, Dy³⁺ is 35 ± 15 nm. Compared with the solid-state reaction and sol-gel method, synthesis temperature of the detonation method is lower about 500 and 200 °C respectively. After being excited under UN lights, detonation soot and that heated at 600–1100 °C can emit a green light.     

Solid phase epitaxy on N-type polysilicon films formed by aluminium induced crystallization of amorphous silicon

In this work, undoped amorphous silicon layers were deposited on n-type AIC seed films and then annealed at different temperatures for epitaxial growth. The epitaxy was carried out using halogen lamps (rapid thermal process or RTP) or a tube conventional furnace (CTP). We investigated the morphology of the resulting 2 µm thick epi-layers by means of optical microscopy. An average grain size of about 40 µm is formed after 90 s annealing at 1000 °C in RTP. The stress and degree of crystallinity of the epi-layers were studied by micro-Raman Spectroscopy and UV–visible spectrometer as a function of annealing time. The presence of compressive stress is observed from the peak position which shifts from 520.0 cm^− 1 to 521.0 cm^− 1 and 522.3 cm^− 1 after CTP annealing for 10 min and 90 min, respectively. It is shown that the full width at half maximum (FWHM) varies from 9.8 cm^− 1 to 15.6 cm^− 1, and the magnitude of stress is changing from 325 MPa to 650 MPa. Finally, the highest crystallinity is achieved after annealing at 1000 °C for 90 min in a tube furnace exhibiting a crystalline fraction of 81.5%. X-ray diffraction technique was used to determine the preferential orientation of the poly-Si thin films formed by SPE technique on n⁺ type AIC layer. The preferential orientation is 100 for all annealing times at 1000 °C.     

Biosensor enhanced by glucose oxidase biomimetic membrane containing the platinum and silica nanoparticles

In this paper, glucose biosensor is fabricated with immobilization of glucose oxidase (GOx) in platinum and silica sol. The glucose biosensor combined with Pt and SiO₂ nanoparticles could make full use of the properties of nanoparticles. A set of experimental results indicates that the current response for the enzyme electrode containing platinum and silica nanoparticles increases from 0.32 µA cm^− 2 to 33 µA cm^− 2 in the solution of 10 mM β-D-glucose. The linear range is 3 × 10^− 5 to 3.8 × 10^− 3 M with a detection limit of 2 × 10^− 5 M at 3σ. The effects of the various volume ratios of Pt and SiO₂ sols with respect to the current response and the stability of the enzyme electrodes are studied.     

High-temperature stability of the mechanical and optical properties of Si–B–C–N films prepared by magnetron sputtering

Quaternary Si–B–C–N materials are becoming increasingly attractive due to their possible high-temperature and harsh-environment applications. In this work, amorphous Si–B–C–N films with two compositions (Si₃₄B₉C₄N₄₉ and Si₃₆B₁₃C₇N₄₀) and low contamination level (H + O + Ar < 4 at.%) were deposited on silicon substrates by reactive dc magnetron co-sputtering using two different targets and gas mixtures. Thermal stability of these films was investigated in terms of composition, bonding structure, as well as mechanical and optical properties after annealing in helium up to a 1300°C substrate limit. Films with a high nitrogen content (Si₃₄B₉C₄N₄₉, i.e. N/[Si + B + C]~ 1.0) were found to be stable up to 1300°C. After annealing, the hardness and elastic recovery of those films slightly increased up to 27 GPa and 84%, respectively, and the reduced Young's modulus remained practically constant (~ 170 GPa). The refractive index and the extinction coefficient at 550 nm were evaluated at 2.0 and 5 × 10^− 4, respectively, and the optical band gap was approximately 3.0 eV. In contrast, films with a lower nitrogen content (Si₃₆B₁₃C₇N₄₀, i.e. N/[Si + B + C]~ 0.7) were stable only up to 1200°C. Both Si–B–C–N materials studied here exhibited extremely high oxidation resistance in air up to the 1300°C substrate limit.     

Structural investigations of sol–gel derived silicate gels using Eu ion-probe luminescence

Undoped and Eu³⁺-doped CaF₂–SiO₂ gels were prepared by the sol–gel method and their optical properties have been studied. The UV–VIS–NIR absorption and photoluminescence spectra have shown the bands typical for the Eu³⁺ ions transitions. When the Eu-doped gel is annealed at temperatures up to 800 °C (i.e. above the CaF₂ crystallisation peak at 460 °C) the photoluminescence spectra intensity increase, the 590 nm (⁵D₀→⁷F₁) and 620 nm (⁵D₀→⁷F₂) luminescence bands become comparable and a structuring of the 620 nm band is observed. The phonon sidebands peaks associated with the ⁵F₀→⁷D₂ transition of the Eu³⁺ ion were observed at around 1000 and 620 cm⁻¹ and have been assigned to the Si–O and Ca–O bonds, respectively. A phonon sideband signal in the range of 300–400 cm⁻¹ was attributed to Ca–F bonds in the precipitated CaF₂ phase. From the optical absorption, photoluminescence and phonon sidebands spectra we have concluded that in the gels annealed at 800 °C, the Eu³⁺ ions are incorporated into the silica network and in the precipitated CaF₂ phase.     

Template-free synthesis of NiO hollow microspheres covered with nanoflakes

α-Ni(OH)₂ hollow microspheres precursors were synthesized without any template through a solvothermal method. Hydrolyzing NiCl₂ in alkaline solution, the Ni(OH)₂ hollow microspheres covered with a disordered covering of perpendicular nanoflakes were prepared. Subsequently, the similar microstructured NiO hollow microspheres with BET area around 222.8 m²/g and specific pore volume around 0.5 cm³/g were obtained by calcining the above precursor at 250–300 °C with a slow heating rate (about 1 K/min). The effects of the surfactant and the calcining temperature on the morphology and the mesostructure of the NiO hollow microspheres were also discussed.     

Physical properties of transparent conducting Cd–Te–In–O thin films: Outlining a thermodynamic system for transparent conducting oxides

Cd–Te–In–O thin films are grown by pulsed laser deposition using a composite target of CdTe powder embedded in an indium matrix. Oxygen pressures range from 2.00 to 6.67 Pa at a substrate temperature of 420 °C. The structure, optical transmission and sheet resistance of the films are measured. Substitutional compounds with In_2 − 2x(Cd,Te)_2xO₃ stoichiometry are found at high oxygen pressures. A ternary phase diagram of the CdO–In₂O₃–TeO₂ system shows the relationship between the structure and the stoichiometry of the films. To evaluate film performance, a figure of merit is proposed based on the relationship between the integral photonic flux and the sheet resistance. The best figure of merit values corresponds to a sample prepared at 3.8 Pa O₂ that consists of (In₂O₃)_0.3(CdTe₂O₅)_0.7 and exhibits an optical band gap of 3.0 eV. This sample is a suitable substrate for electrodeposition due to its good electrochemical stability.     

Si diffusion in magnetron sputtered silicon carbide films deposited on silicon and carbon substrates

Self-diffusion of silicon in magnetron sputtered silicon carbide films deposited on different substrates (crystalline silicon and glassy carbon) is investigated. Since crystallization of amorphous silicon carbide films strongly depends on the substrate, the diffusivity of silicon is expected to depend on the substrate as well. Isotope hetero-structures and secondary ion mass spectrometry were used for analysis. For amorphous samples an upper limit of the diffusivity of 1 × 10^− 21 m²/s is derived at 1100 C°. For crystallized films diffusivities between 1350 °C and 1600 °C are found to be not significantly different for the two types of substrates. For samples deposited on glassy carbon substrates an activation enthalpy ΔH_D = (8.7 ± 0.9) eV was found for the self-diffusion of Si. The consequences of our findings for crystallization are discussed.     

Luminescence properties of Ammonium Silicon Fluoride films prepared by vapour etching technique

Photoluminescence (PL) properties of Ammonium Silicon Fluoride samples prepared by vapour etching technique are investigated with respect to excitation energy, excitation intensity and temperature. Ageing effect at ambient conditions is also examined by Fourier Transform Infrared Spectroscopy. PL peak maximum blue shifts as the excitation intensity increases and saturates at 2.106 eV. Temperature-dependent variations in PL peak energies and intensities cannot be thoroughly elucidated via Quantum Confinement model alone and require consideration of recombination rates at Si–SiO_x interface. Temperature dependence of integrated PL intensity is treated by a three-component functional form.Infrared absorption bands at 1060 cm^− 1, 1113 cm^− 1 and 1230 cm^− 1 attain saturation with time. Agreement between the saturation time of SiO_x longitudinal optic mode at 1230 cm^− 1 and that deduced from PL measurements in literature is noted. It is shown that PL emissions are intrinsic in nature and have a significant excitonic contribution.     

Bending strength and effective modulus of atmospheric ice

Bending strength and the effective modulus of atmospheric ice accumulated in a closed loop wind tunnel at temperatures − 6 °C, − 10 °C and − 20 °C with a liquid water content of 2.5 g/m³ have been studied at different strain rates. More than 120 tests have been conducted. Ice samples, accumulated at each temperature, have been tested at the accumulation temperature. In addition, tests have been performed at temperatures of − 3 °C and − 20 °C, for the ice accumulated at − 10 °C. These tests showed a clear dependency of bending strength of atmospheric ice on test temperature at low strain rates. Strain rate effects are implied because the spread in bending strength for the different temperatures diminishes as strain rate increases. The results also reveal that, in most cases, the effective modulus of atmospheric ice increases with increasing strain rate. The bending strength of atmospheric ice accumulated at − 10 °C has been found to be greater than that of ice accumulated at − 6 °C and − 20 °C. The results show that the effective modulus of ice accumulated at − 20 °C at higher strain rates is less than that of the two other types.     

Flow boiling heat transfer to carbon dioxide: general prediction method

An updated version of the Kattan–Thome–Favrat flow pattern based, flow boiling heat transfer model for horizontal tubes has been developed specifically for CO₂. Because CO₂ has a low critical temperature and hence high evaporating pressures compared to our previous database, it was found necessary to first correct the nucleate pool boiling correlation to better describe CO₂ at high reduced pressures and secondly to include a boiling suppression factor on the nucleate boiling heat transfer coefficient to capture the trends in the flow boiling data. The new method predicts 73% of the CO₂ database (404 data points) to within ±20% and 86% to within ±30% over the vapor quality range of 2–91%. The database covers five tube diameters from 0.79 to 10.06 mm, mass velocities from 85 to 1440 kg m⁻² s⁻¹, heat fluxes from 5 to 36 kW m⁻², saturation temperatures from −25 °C to +25 °C and saturation pressures from 1.7 to 6.4 MPa (reduced pressures up to 0.87).     

Synthesis and characterization of nanocrystalline manganese pyrophosphate Mn2P2O7

Mn₂P₂O₇ polyhedral particles were synthesized by simple and cost-effective method using manganese nitrate hydrate and phosphoric acid in the presence of nitric acid with further calcinations at the temperature of 800 °C. The crystallite size obtained from X-ray line broadening is 31 ± 13 nm for the Mn₂P₂O₇. The X-ray diffraction and SEM results indicated that the synthesized nanoparticles have only the structure without the presence of any other phase impurities. The FT-IR and FT-Raman spectra show characteristic bands of the P₂O₇⁴⁻ anion. The UV–Vis–NIR spectrum confirms the octahedral coordination of Mn²⁺ ion.     

Growth and optical characterizations of (Ba0.32Sr0.68)5Nb4O15 crystal

(Ba_0.32Sr_0.68)₅Nb₄O₁₅ crystal with sizes of Ø 17 × 35 mm was grown successfully by Czochralski technique method. The thermal anisotropy was discussed. The principal coefficients of thermal expansion along (100), (010), (001) directions were precisely measured to be 1.308 × 10^− 5, 1.288 × 10^− 5, 1.478 × 10^− 5 K^− 1, respectively. Its optical transparency range has been measured and found to span from 323 to 5500 nm. The bands present in the IR spectra were identified and assigned to the corresponding vibration modes of NbO₆ anions.     

Low-temperature fabrication of 0.65 PMN–0.35 PT by a mixed oxide method

Single-phase perovskite 0.65 PMN–0.35 PT was achieved at low temperature by a conventional mixed oxide method. It was prepared by ball-milling a mixture of PbO(orthorhombic), TiO₂, Nb₂O₅ and (MgCO₃)₄Mg(OH)₂·5H₂O instead of MgO and heat treatment at 800 °C for 2 h. The formation was studied by means of DSC, FT-IR, Coupled TG-Mass, XRD, and SEM. It proceeded via formation of PbO(tetragonal) and Pb₂Nb₂O₇(P₂N) intermediates to form perovskite phase. The pure perovskite PMN-PT powder was obtained in particle size of 0.5–0.8 μm, agglomerate-free, and pseudo-cube. The powder calcined at 600 °C was sintered to 97% T.D. at 900–1000 °C for 2 h and showed room temperature dielectric constant of 3200, loss of 1–2%, and specific resistance of 5 × 10¹¹ Ω cm.     

Study on Li-ion diffusion in nano-crystalline LiMn2O4 thin film cathode grown by pulsed laser deposition using CV, EIS and PITT techniques

In the present work, LiMn₂O₄ thin films have been prepared by pulsed laser deposition on stainless steel substrates. The films deposited at 400 °C and 200 mTorr of oxygen were mainly composed of nano-crystals less than 100 nm and their agglomerates. Three different electrochemical methods including CV, EIS and PITT were applied to measure the overall Li⁺-ion diffusion coefficients and charge-transfer resistances at various potentials from 3.85 to 4.5 V. The Li⁺ diffusion coefficients were in the range of 10⁻¹² to 10⁻¹⁰ cm² s⁻¹, depending on the potentials. It was found that the charge-transfer resistances decreased with the increase of potentials. Especially, relatively high diffusion coefficients and low charge-transfer resistances were observed above 4.2 V.