Electrochromic properties of lithiated Co-oxide (LixCoO2) and Ni-oxide (LixNiO2) thin films prepared by the sol–gel route

Layered Li_xCoO₂ and Li_xNiO₂ thin films (x1) were prepared by a peroxo wet chemistry route from Li(I), Co(II) and Ni(II) acetate precursors and the addition of H₂O₂. Structural changes during the processing of xerogel to final oxide were followed by X-ray diffraction and infrared spectroscopy. Electrochromic properties were determined with in-situ potentiodynamic, potentiostatic and galvanostatic spectroelectrochemical measurements. Single dipped films with composition Li_0.99Co_1.01O₂ or Li_0.94Ni_1.06O₂ exhibited stable voltammetric response in 1 M LiClO₄/propylene carbonate electrolyte after about 60 cycles. The total charge exchanged in a reversible charging/discharging cycle was about ±30 mC cm⁻² for Li_0.99Co_1.01O₂ and ±20 mC cm⁻² for Li_0.94Ni_1.06O₂ oxide films. Galvanostatic measurements showed that about 1/2 (x0.5) and 2/3 (x0.3) of Li⁺ ions could be reversibly removed from the structure of Li_0.99Co_1.01O₂ and Li_0.94Ni_1.06O₂ films, respectively. Practical applicability of Li_0.99Co_1.01O₂ and Li_0.94Ni_1.06O₂ oxide films was studied in electrochromic devices with WO₃(H⁺)Li⁺ormolyteLi_0.99Co_1.01O₂ and WO₃(H⁺)Li⁺ormolyteLi_0.94Ni_1.06O₂ configuration. The monochromatic transmittance T_s (λ=633 nm) of dark blue coloured devices was extremely low (T_s3%), whereas in bleached state the value reached around T_s70%.     

Angle-resolved optical characterisation of an electrochromic device

An electrochromic prototype with WO₃ and NiO as electrochromic layers was analysed in an absolute spectrophotometer. The electrochromic glazing was measured in combination with a clear float glass and a low-e glass in order to simulate a ‘real’ window. Similar measurements were performed on a commercial electrochromic product, i.e., a Gentex Night Vision Safety™ (NVS^®) mirror from Gentex Corporation, and the results were compared. The spectral transmittance was measured, in bleached and coloured state, over the solar wavelength range at the angles of incidence, φ=0, 40, 60 and 70°. The direct solar transmittance, T_sol, the visual transmittance, T_vis, and the angular dependence for these parameters were calculated.     

Electrical and optical properties of F-doped textured SnO2 films deposited by APCVD

This paper presents the structural, electrical and optical properties of transparent conducting F-doped textured SnO₂ films prepared by atmosphere pressure chemical vapour deposition (APCVD). Polycrystalline SnO₂:F films having a variable preferred orientation have been obtained with resistivity as low as 5 × 10⁻⁴ Ωcm, with carrier concentrations between 3.5 × 10²⁰ and 7 × 10²⁰ cm⁻³, and Hall mobilities from 15.7 to 20.1 cm²/V/s. The average transmittance (including diffusion transmittance) is as high as 94% in the wavelength range of the visible spectrum and the maximum infrared reflectance reaches 92% for a film 655 nm thick. The figure of merit ƒ_TC = T10/_sh, (7.12 × 10⁻² S) of these films is the highest amongst the results reported on doped SnO₂ films.     

Characterization of Cu(InxGa1−x)2Se3.5 thin films prepared by rf sputtering

Cu(In_xGa_1−x)₂Se_3.5 thin films were fabricated by rf sputtering from CuIn_xGa_1−xSe₂ and Na mixture target by controlling the mixture ratio. X-ray diffraction analyses show that the structure of Cu(In_xGa_1−x)₂Se_3.5, thin films is different from chalcopyrite structure: especially, CuIn₂Se_3.5 thin films have a defect chalcopyrite structure. The lattice parameters for Cu(In_xGa_1−x)₂Se_3.5 thin film are slightly smaller than those for CuIn_xGa_1−xSe₂ thin film and linearly decreased with increasing Ga content. The optical absorption coefficients for Cu(In_xGa_1−x)₂Se_3.5, thin films exceed 2 × 10⁴ cm⁻¹ in energy region above the fundamental band edge. The band gap for Cu(In_xGa_1−x)₂Se_3.5 thin films is larger than that for CuIn.Ga_1−x2Se₂ with the same Ga content and increased with increasing Ga content.     

Synthesis and characterization of rough electrochromic phosphotungstic acid films obtained by spray-gel process

Rough electrochromic phosphotungstic acid (PWA) films were fabricated by spraying a gel of phosphotungstate anions with a molar ratio of P:W=1:12 onto glass substrates. The substrates were coated with transparent and electrically conducting SnO₂:F at 300°C. Analysis by X-ray photoelectron spectroscopy determined that the P:W molar ratio in the films was approximately 1:14. Infrared spectroscopy and X-ray diffraction showed that the film is a form of polycrystalline phosphotungstic acid. SEM micrographs showed that the films have a rough morphology based on fiber-shape bridges. Optoelectrochemical measurements demonstrated pronounced electrochromism in the PWA films upon H⁺ intercalation/deintercalation with a high diffuse reflectance (R_d) and transmittance (T_d). We found for as-deposited films that R_d/total reflectance (R_t) and T_d/total transmittance (T_t) at 550 nm was around 0.83 and 0.68, respectively. This ratio decreases at bleached state to 0.74 and 0.41 for R_d/R_t and T_d/T_t, respectively.     

Studies on membrane viscosity stabilized solar pond

In this nonsalt type of solar pond, the nonconvecting layer is composed of a viscous polymer solution partitioned by a number of transparent films. An advantage of partitioning is that a thinner polymer solution can be used and that the light transmittance increases. Results of experimental and theoretical investigations on the performance of this solar pond are summarized as follows:

1. 1. Ionized polyacrylamide solution was chosen as the thickener based on tests about solubility, viscosity, light transmittance and stability.

2. 2. The critical temperature difference for the onset of convection in the polymer layer (ΔT/L)_cr [°C/m] was given by the following formula based on the measurements in various thicknesses of the polymer layers (L) [m] and various concentrations (ζ) [%],

(ΔT/l)_cr=(55−185lnL)exp(4.66L^0.505lnζ

3. 3. An outdoor model pond, 200 × 150 cm surface and 100 cm depth, was constructed in Osaka. Four types of model ponds were tested, and the availability of membrane type with partition films was confirmed.

4. 4. The theoretical temperature rise of the pond using a one-dimensional model was calculated by solving the equations of the heat balance in the pond. As a result, the optimum values of thickness of polymer layer and number of films was determined

     

Temperature effect on the electrical and optical properties of indium-selenide thin-films

Indium-Selenide thin-films have been prepared by the thermal-evaporation technique at a pressure of 4.5×10⁻⁶ torr and a temperature of 673–873 K. For both the as-deposited and annealed films, (i) the electrical conductivity increased with increasing temperature and (ii) the variation of activation energy follows the island structure theory. The temperature co-efficient of resistance (T.C.R.) and Hall-effect measurements indicate that the sample is a n-type carrier. The optical spectra for both types of films were obtained in the wavelength range 0.3<λ<2.5 μm, and by comparing the magnitude of transmittance spectra, it is found that the annealed films are more transparent than the as-deposited ones in the UV and visible range. The integrated transmittance and reflectance values were obtained: the high values of T_lum and T_sol for the annealed films suggest that indium selenide may be used in selective-surface devices.     

Porous nickel MCFC cathode coated by potentiostatically deposited cobalt oxide: II. Structural and morphological behavior in molten carbonate

Cobalt oxide was deposited on porous nickel by an electrodeposition technique as precursor of a novel MCFC cathode. The behavior of this cathode in molten (Li_0.52Na_0.48)₂CO₃ eutectics at 650 °C under an atmosphere of CO₂:air (30:70) was studied before and after 50 h of exposure by different techniques. Before the exposure, the deposit of cobalt corresponded to a Co₃O₄ thin layer of. This crystalline structure was identified by XRD and Raman spectroscopy. After its exposure in the eutectic melt a loss of cobalt was observed by XRD, Raman spectroscopy, XPS, EDS and ICP-AES. The change in the Co₃O₄ structure into lithium–cobalt–nickel oxide (LiCo_1−yNi_yO₂) was observed by Raman spectroscopy. The SEM micrographs for Co₃O₄-coated porous nickel showed different angular shapes with respect to porous Ni. The nickel solubility for the coated porous nickel, measured by ICP-AES, decreased with respect to uncoated nickel. The Co₃O₄-coated porous nickel cathode showed, after its immersion in the molten carbonate melt, a similar porosity but a higher pore size. LiCo_1−yNi_yO₂-coated NiO offers interesting features which combine the properties of nickel, lithium and cobalt in molten carbonate. This could be a promising novel MCFC cathode material.     

Electrochromic Devices Incorporating Cr Oxide And Ni Oxide Films:: A Comparison

Transparent films of Cr oxide and Ni oxide were made by reactive DC magnetron sputtering in Ar+O₂+H₂. They displayed anodic electrochromism with charge capacities similar to that of W oxide. Cr oxide was stable in acidic environments, while Ni oxide was stable in basic environments. Electrochromic devices were made with pristine Cr oxide or Ni oxide films operating in conjunction with W oxide and a proton conducting electrolyte. Of the two oxides, Cr oxide film allowed device operation at a lower voltage span, while the device with Ni oxide film yielded a higher transmittance in the bleached state, a larger absorptance modulation, and a more neutral color.     

Electrochemical performance of Nd0.6Sr0.4Co0.5Fe0.5O3−δ–Ag composite cathodes in intermediate temperature solid oxide fuel cells

The electrochemical performances of Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ–Ag composite cathodes have been investigated in intermediate temperature solid oxide fuel cells. The Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ–Ag cathodes prepared by ball milling followed by firing at 920 °C show the maximum performance (power density: 0.15 W cm⁻² at 800 °C) at 3 wt.% Ag. On the other hand, the Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ–Ag composite cathodes with 0.1 mg cm⁻² (0.5 wt.%) Ag that were prepared by an impregnation of Ag into Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ followed by firing at 700 °C (but the electrolyte–Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ assembly was prepared first by firing at 1100 °C) exhibit much better performance (power density: 0.27 W cm⁻² at 800 °C) than the composite cathodes prepared by ball milling, despite a much smaller amount of Ag due to a better dispersion and an enhanced adhesion. AC impedance analysis indicates that the Ag catalysts dispersed in the porous Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ cathode reduce the ohmic and the polarization resistances due to an increased electronic conductivity and enhanced electrocatalytic activity.     

Structural and electrochromic properties of nanosized Fe/V-oxide films with FeVO4 and Fe2V4O13 grains: comparative studies with crystalline V2O5

Various mixed Fe/V-oxides can be used as anodes in Li⁺ rocking chair batteries, however, their small optical modulation during the insertion/extraction of Li⁺ ions makes them candidates for the counter electrodes in electrochromic (EC) devices. The sol–gel route in combination with dip-coating deposition was used for the preparation of Fe/V-oxide films with molar ratios Fe:V=0.1:1, 1:2, 1:1 and 2:1. X-ray diffraction combined with Fourier transform infrared (FT-IR) spectroscopy studies of films and powders reveal that heating of xerogel films at 400°C produces films with nanosized FeVO₄ (Fe:V=1:1) and Fe₂V₄O₁₃ (Fe:V=1:2) grains, while the corresponding crystalline powders were obtained at 500°C (8 h). Charge capacities (Q) of Fe/V-oxide films (300 and 400°C) were determined using cyclic voltammetry (CV) from 1.5 to −1.5 V vs. Ag/AgCl (4.8 to 1.8 V vs. Li) in 1 M LiClO₄/propylene carbonate (PC) electrolyte. Our results revealed that Q values of Fe/V-oxide films are up to 20 mC cm⁻² depending on the thickness (40–100 nm), temperature of heating and the Fe:V molar ratio (1:2, 1:1). During the first 300 cycles the cycling stability of the Fe-containing films is better than that of V₂O₅ crystalline films. UV-visible spectra of charged/discharged films revealed that these films, similar to V₂O₅ films, exhibit a mixed anodic/cathodic electrochromism. It was established that with regard to the colouring/bleaching changes of V₂O₅ crystalline films, the Fe/V-oxide films exhibit smaller cathodic colouring at wavelengths λ>600 nm and higher visible transmittance. IR spectroscopy of charged/discharged Fe/V-oxide films confirmed that the reduction of Fe³⁺ prevents the overreduction of V⁵⁺ to V³⁺, which takes place in V₂O₅ films cycled in the same potential range.     

Preparation and properties of sprayed CuGa0.5In0.5Se2 thin films

CuGa_0.5In_0.5Se₂ thin films were prepared by spray pyrolysis technique at substrate temperatures (T_s) in the range 100–400°C. The films prepared at T_s = 300–350°C were nearly stoichiometric, polycrystalline with a strong preferred (112) orientation. The resistivity of the films varied in the range, 50–1000 Ω cm and the evaluated optical band gap was 1.35 eV.     

电沉积法制备电致变色材料

应用电沉积法制备WO3、NiO、M0O3,WO3/M0O3等电致变色薄膜。WO3薄膜、NiO薄膜、M0O3薄膜具有较好的电致变色特性,漂白态和着色态的透射率之差平均为30％左右。WO3/M0O3掺杂薄膜漂白态和着色态的透射率之差平均为40％左右,显示掺杂有利于增强薄膜的电致变色特性。WO3 NiO互补型电致变色体系漂白态和着色态的透射率之差平均为40％左右,显示互补型电致变色材料有利于增强电致变色特性。在双注入模型的基础上,根据过渡金属配合物显色机理,提出解释电致变色机理的“配位场模型”,认为在电致变色中可能存在三种电子跃迁方式。     

The gasochromic properties of sol–gel WO3 films with sputtered Pt catalyst

Gasochromic films are receiving considerable attention, stimulated by the need for switchable windows that compete with more complex electrochromic ‘smart’ windows for building applications. The latest development of WO₃ films, prepared by the sol–gel route and dip-coating deposition overlaid by a thin layer of sputtered Pt metal, are presented. Colouring/bleaching kinetics of WO₃ films and WO₃ films in which a hybrid organic/inorganic sol–gel precursor (ormosil) has been added are evaluated. Results revealed that with respect to velocity of coloration, sol–gel WO₃ gasochromic films compete with the sputtered ones. Many aspects of the colouring/bleaching behaviour of the films resemble that of sputtered Pt/WO₃ films and thus confirm the similarity in the colouring/bleaching mechanisms. IR spectroscopy revealed the presence of well-defined W=O and the breaking of W–O bonds indicating the formation of H⁺… ⁻OW- and WO_3−x species in coloured films.     

Preparation and properties of LiCoyMnxNi1−x−yO2 as a cathode for lithium ion batteries

The preparation of LiCo_yMn_xNi_1−x−yO₂ from LiOH·H₂O, Ni(OH)₂ and γ-MnOOH in air was studied in detail. Single-phase LiCo_yMn_xNi_1−x−yO₂ (0y0.3 and x=0.2) is obtained by heating at 830–900°C. The optimum heating temperatures are 850°C for y=0–0.1 and 900°C for y=0.2–0.3. Excess lithium (1z1.11 for y=0.2) and the Co doping level (0.05y0.2) do not significantly affect the discharge capacity of Li_zCo_yMn_0.2Ni_0.8−yO₂. The doping of Co into LiMn_0.2Ni_0.8O₂ accelerates the oxidation of the transition metal ion, and suppresses partial cation mixing. Since the valence of the manganese ion in LiMn_0.2Ni_0.8O₂ is determined to be 4, the formation of a solid solution between LiCo_yNi_1−yO₂ and Li₂MnO₃ is confirmed.     

NiOxHy薄膜电致变色性能的研究

利用直流磁控溅射法，在Ｏ２＋Ｈ２的气氛下制备了ＮｉＯｘＨｙ薄膜，研究了不同氢气含量对薄膜的初始沉积态、漂白态和着色态透光性能的影响，含氢量为８０％时，薄膜的初始沉积态的平均可见光透射比最高。含氢量为６０％时，薄膜的电致变色能力最佳。用获得的ＮｉＯｘＨｙ薄膜制备的反射型全固态电致变色器件的控光范围可达７７％。对ＮｉＯｘＨｙ薄膜三种状态的红外吸收光谱分析表明，ＮｉＯｘＨｙ薄膜的变色机理可用：Ｎｉ（ＯＨ）２（漂白态）＝ＮｉＯＯＨ（着色态）＋Ｈ＋＋ｅ－表示。     

A screen-printed Ce0.8Sm0.2O1.9 film solid oxide fuel cell with a Ba0.5Sr0.5Co0.8Fe0.2O3−δ cathode

Screen-printing technology was developed to fabricate Ce_0.8Sm_0.2O_1.9 (SDC) electrolyte films onto porous NiO–SDC green anode substrates. After sintering at 1400 °C for 4 h, a gas-tight SDC film with a thickness of 12 μm was obtained. A novel cathode material of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ was subsequently applied onto the sintered SDC electrolyte film also by screen-printing and sintered at 970 °C for 3 h to get a single cell. A fuel cell of Ni–SDC/SDC (12 μm)/Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ provides the maximum power densities of 1280, 1080, 670, 370, 180 and 73 mW cm⁻² at 650, 600, 555, 505, 455 and 405 °C, respectively, using hydrogen as fuel and stationary air as oxidant. When dry methane was used as fuel, the maximum power densities are 876, 568, 346 and 114 mW cm⁻² at 650, 600, 555 and 505 °C, respectively. The present fuel cell shows excellent performance at lowered temperatures.     

Preparation and properties of transparent conducting zinc oxide and aluminium-doped zinc oxide films prepared by evaporating method

Undoped and aluminium-doped zinc oxide films have been prepared by thermal evaporation of zinc acetate [Zn(CH₃COO)₂ 2H₂O] and aluminium chloride [AlCl₃] onto a heated glass substrate. The structural and optoelectrical properties of the films have been studied. The effects of heat treatment for the as-deposited films in air and vaccum are investigated. Highly transparent films with conductivity as low as 2×10⁻³ Ω cm can be produced by controlling the deposition parameters. The electron carrier densities are in the range 0.2–7×10¹⁹ cm⁻³ with mobilities of 22–58 cm² V⁻¹ s⁻¹.     

Collector and storage efficiencies in solar heating systems

A general definition of the effective efficiency of solar collector operating in a solar energy system is presented which gives a fair method of comparison of different collectors operating in that particular application. Based on comparison between the area required for the actual collector and that of a perfect collector-both giving the same fraction solar—the definition permits the definition of the effective average value of the collector input parameter, P = (T_fi − T_a)/S. The concept of the perfect collector also leads to a fair definition for the efficiency of the storage component in a solar heating system. These parameters are evaluated for the special case of residential space heating and service hot water systems of the standardized f-chart type operating in a number of Canadian cities. Simple methods for collector comparisons result from the study and indications are that a simple solar system design method will follow.     

Preparation of Culn(SxSe1−x)2 thin films by sulfurization and selenization

A CuIn(S_xSe_1−x)₂ alloy thin-film was prepared by selenization of CuInS₂: its composition ratio x can be controlled by the number of selenization cycles implemented. Crystallinity of the films was improved by annealing in vacuum. The resistivity of the film was about 1 Ω cm and increased by one to two orders of magnitude after KCN treatment. An 8.1 % efficiency solar cell was obtained by using this annealed alloy thin-film.