Cadmium Indate Research Articles

Hydrogen evolution by templated cadmium indate nanoparticles under natural sunlight illumination

Carbon-doped cadmium indate (CdIn2O4) nanoparticles were synthesized by a sol–gel templating method using the block co-polymer surfactant Pluronic F127 and evaluated for hydrogen generation activity under artificial and natural solar illumination. Each catalyst powder was loaded with platinum as a cocatalyst in order to promote charge carrier separation. BET surface area measurements indicated an increase in surface area with F127 introduction of up to 5 times the area of the non-templated sample. Natural sunlight illumination experiments showed the hydrogen evolution rate of CdIn2O4 was 17 μmol h−1 as compared to 2.1 μmol h−1 for the Pt:TiO2 reference material. The H2 rate was determined to be similar under both stirring and non-stirring conditions for the CdIn2O4 catalyst, which resulted from 10 min irradiation exposure times. Laboratory experiments confirmed this effect and showed that at longer, out to 60 min, irradiation times the evolution rate was 3 times greater for stirred over non-stirred samples. The templated nanoparticle CdIn2O4 catalysts are promising for solar hydrogen conversion.

Efficient Photocatalytic Hydrogen Production by Platinum-Loaded Carbon-Doped Cadmium Indate Nanoparticles

Undoped and carbon doped cadmium indate (CdIn(2)O(4)) powders were synthesized using a sol-gel pyrolysis method and evaluated for hydrogen generation activity under UV-visible irradiation without the use of a sacrificial reagent. Each catalyst powder was loaded with a platinum cocatalyst in order to increase electron-hole pair separation and promote surface reactions. Carbon-doped indium oxide and cadmium oxide were also prepared and analyzed for comparison. UV-vis diffuse reflectance spectra indicate the band gap for C-CdIn(2)O(4) to be 2.3 eV. C-doped In(2)O(4) showed a hydrogen generation rate approximately double that of the undoped material. When compared to platinized TiO(2) in methanol, which was used as a control material, C-CdIn(2)O(4) showed a 4-fold increase in hydrogen production. The quantum efficiency of the material was calculated at different wavelength intervals and found to be 8.7% at 420-440 nm. The material was capable of hydrogen generation using visible light only and with good efficiency even at 510 nm.

Photoelectrochemical evaluation of undoped and C-doped CdIn 2O 4 thin film electrodes

Undoped and C-doped cadmium indate (CdIn 2O 4) thin films and powders were synthesized, characterized, and evaluated for photoelectrochemical water splitting. Both undoped and C-doped CdIn 2O 4 samples have cubic lattices, and the presence of carbonate-type species was confirmed in the C-doped sample by XPS. Doping C into CdIn 2O 4 leads to a red shift (but no separate peak) in light absorption and band gap narrowing. The photocurrent densities of CdIn 2O 4 electrodes are at least three-fold greater than either CdO or In 2O 3 electrodes with equivalent film thickness. Carbon doping further improved the photocurrent densities by 33%. The photoelectrochemical performance of C-doped CdIn 2O 4 was optimized with respect to several synthetic parameters, including the C:In molar ratio and glucose concentration in the spray precursor solution, the calcination temperature, and the film thickness. The present work shows that CdIn 2O 4 is a promising photocatalyst and can be suitably doped to improve the electrochemical properties for solar conversion applications.

Electrical resistivity dependence of semi-conductive oxide electrode on the label-free electrochemical detection of DNA

The paper reports on the influence of electrical resistivity of bio-modified transparent and conductive oxide (TCO) electrodes on the sensitivity to DNA hybridization in term of impedance variation. We have deposited pure cadmium indate (CdIn 2O 4) film electrodes on glass substrates by aerosol pyrolysis. By adjusting the film deposition conditions, films with a wide range of resistivity ranging between 4 × 10 −4 and 2 × 10 −3 Ω cm were obtained. Using electrochemical impedance spectroscopy (EIS), we showed that the behaviour of bare films is typical of semiconductor electrode with flat band potentials depending on the film resistivity. Then we studied the electrochemical behaviour of the biomodified electrodes before and after DNA hybridization. The impedance variation due to DNA hybridization was particularly studied in the low frequency range where large and significant increases were observed. These increases were studied in term of calculated polarisation resistance R p. For all films, R p variation is potential dependant and is maximum between −0.1 and 0 V/ref. In this range of potential, the magnitude of this variation increases with the film resistivity. This behaviour is explained by the relationship between the field effect phenomenon, the thickness of the space charge region and the film electrical resistivity. This work shows that, in the case of metallic semi-conductive oxide electrode, the sensitivity to the DNA detection increases with the electrode resistivity.

Cadmium oxide, indium oxide and cadmium indate thin films obtained by the sol–gel technique

Thin films of the mixed CdO-In 2O 3 system were deposited on glass substrates by the sol–gel technique. The precursor solution was obtained starting from the mixture of two precursor solutions of CdO and In 2O 3 prepared separately at room temperature. The In atomic concentration percentages ( X) in the precursor solution with respect to Cd (1 − X ), were: 0, 16, 33, 50, 67, 84 and 100. The films were sintered at two different sintering temperatures (Ts) 450 and 550 °C, and after that, annealed in a 96:4 N 2/H 2 gas mixture at 350 °C. X-ray diffraction patterns showed three types of films, excluding those constituted only of CdO and In 2O 3 crystals: i) For X ≤ 50 at.%, the films were constituted of CdO + CdIn 2O 4 crystals, ii) For X = 67 at.%, the films were only formed of CdIn 2O 4 crystals and iii) For X = 84 at.% the films were constituted of In 2O 3 + CdIn 2O 4 crystals. In all films in the 0 < X < 100 range, the formation CdIn 2O 4 crystals of this material was prioritized with respect to the formation of CdO and In 2O 3 materials. All films showed high optical transmission and an increase of the direct band gap value from 2.4 (for CdO) to 3.6 eV (for In 2O 3), as the X value increases. The resistivity values obtained were in the interval of 8 × 10 − 4 Ω cm to 10 6 Ω cm. The CdIn 2O 4 films had a resistivity value of 8 × 10 − 3 Ω cm and a band gap value of 3.3 eV.

Cadmium indate thin films, as transparent conducting oxides, obtained by the sol–gel technique

Cadmium indate (CdIn 2O 4) thin films were deposited on glass substrates by the sol–gel technique, starting from the mixture of two simple precursor solutions of CdO and In 2O 3 obtained at room temperature. The In atomic concentration percentage ( X) in the precursor solution with respect to Cd (1− X) was varied from 55 to 79 at% with steps of 4 at%. The films were sintered in an open atmosphere at 550 °C and after that, exposed to different annealing treatments, 96/4 N 2/H 2 gas mixture, H 2 and vacuum, at different temperatures. X-ray diffraction patterns showed three types of films, consisting of crystals of (a) CdO+CdIn 2O 4, (b) CdIn 2O 4 and (c) In 2O 3+CdIn 2O 4. It was found that the films with X≤59 at% and annealed at 600 °C in vacuum for 60 min, showed the lowest resistivity, ∼1×10 −3 Ω cm. The carrier concentration and mobility were determined from Hall measurements. The films were highly transparent (∼80%) in the 400–1100 nm range. In addition to the low-resistivity value and high transparency, the CdIn 2O 4 films had a direct bandgap around 3.2 eV, which shows the importance of using this oxide as a transparent electrode in solar cells.

Optical, electrical and structural properties of indium-doped cadmium oxide films obtained by the sol–gel technique

Indium-doped cadmium oxide films were obtained by mixing cadmium oxide and indium oxide precursor solutions by the sol–gel technique. The indium atomic concentrations in solution ( x) studied were 0, 2, 5 and 10 at%. The films were sintered at two different sintering temperatures ( T s) 350 and 450 °C, and after that annealed in a 96:4 N 2/H 2 gas mixture atmosphere at 350 °C. X-ray diffraction patterns showed that all films sintered at T s=350 °C only consisted of cadmium oxide crystals. The films sintered at T s=450 °C consisted of cadmium oxide crystals also; however, for the highest indium atomic concentration (10 at%) the formation of cadmium indate oxide crystals was evident. All films show high optical transmission (>85%) and an increase of the direct band gap value from 2.4 to 3.1 eV, as the indium atomic concentration in solution increases. The minimum resistivity value obtained was 6.3×10 −4 Ω cm for the films with x=5 at%, T s=450 °C and annealed at 350 °C.

Structural, electronic and optical properties of spinel oxides: cadmium gallate and cadmium indate

The structural, electronic and optical properties of two principal representatives of spinel oxides CdGa2O4 and CdIn2O4 have been investigated using the full-potential augmented plane-wave plus local orbitals method within density functional theory. We used the generalized gradient approximation (GGA) for the exchange-correlation (XC) potential. Moreover, the alternative form of GGA proposed by Engel and Vosko (GGA-EV) is also used for the band structure calculations. The equilibrium lattice constants and the internal parameters are in agreement with the available experimental results. Results obtained for band structure using GGA-EV show a significant improvement over other theoretical work and are closer to the experimental data. The pressure dependence of band gaps is investigated. The dielectric function, reflectivity spectra and refractive index are calculated up to 50 eV. Pressure and volume dependence of the static refractive index have been also calculated.

Characterization of dc reactive magnetron sputtered cadmium indate films

Thin films of cadmium indate were deposited onto the glass substrates by employing dc magnetron sputtering from cadmium–indium alloy target under various substrate temperatures in the range 373–673 K. The films were characterized by studying their structural and electrical properties. The films formed at substrate temperature <423 K were amorphous while those deposited at ≥423 K were polycrystalline with cubic spinel structure. The films prepared at a substrate temperature of 673 K exhibited low electrical resistivity of 3.5 × 10 −4 Ω cm and Hall mobility of 29 cm 2/V s.

Structure, electrical and optical properties of dc magnetron sputtered cadmium indate films: Effect of substrate temperature

Cadmium indate films were deposited by dc reactive magnetron sputtering onto glass substrates in an oxygen partial pressure of 5 × 10 − 4 mbar and at various substrate temperatures in the range 373–673 K. The influence of substrate temperature on the structural, electrical and optical properties of the films was systematically studied. The films formed at substrate temperatures < 423 K were amorphous while those deposited at ≥ 423 K were polycrystalline with cubic spinel structure. The decrease of electrical resistivity and increase of Hall mobility with the increase of substrate temperature were due to the improvement in the crystallinity of the films. The temperature dependence of Hall mobility measurements indicated that the grain boundary scattering of charge carriers was predominant in the films. The films formed at a substrate temperature of 673 K exhibited an electrical resistivity of 3.5 × 10 − 4 Ω cm, Hall mobility of 29 cm 2 V − 1 s − 1 , optical transmittance of 88%, optical band gap of 3.28 eV and figure of merit of 5 × 10 − 2 Ω − 1 .

Structure and electrical properties of CdIn2O4 thin films sputtered at elevated substrate temperatures

A Hall mobility as high as 39.4 cm2 V−1 s−1 was obtained for cadmium indate (CdIn2O4) thin films deposited by rf reactive sputtering from a Cd–In alloy target. The structural and electrical properties for both as-sputtered and after-annealed thin films were studied as a function of the substrate temperatures. The results revealed that elevated substrate temperatures favour the formation of CdIn2O4 thin films with spinel phase. The electrical properties can be understood by a combination of the occupancy of In cations on the tetrahedral vacancies in the spinel unit cell at the elevated substrate temperatures and the formation of oxygen vacancies originating from off-stoichiometry. It can be inferred that the presence of secondary phases in the CdIn2O4 thin films deposited in an oxygen-deficient atmosphere is responsible for their electrical properties. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Transparent conductive cadmium indate thin films prepared by dc magnetron sputtering

Transparent conducting cadmium indate films were deposited at different oxygen partial pressures in the range from 1×10−4 to 5×10−3mbar onto glass substrates maintained at a temperature of 523K by dc magnetron sputtering from a cadmium–indium alloy target at a sputtering pressure of 4×10−2mbar. The films were characterised by studying the influence of oxygen partial pressure on the structural, electrical and optical properties. Cadmium indate films formed at an oxygen partial pressure of 5×10−4mbar were polycrystalline with cubic spinel structure, low electrical resistivity of 1.2×10−3Ωcm, high optical transmittance of 87% in the visible region, optical band gap of 3.23eV and a figure of merit of 1.8×10−3Ω−1.

Phase Relationships, Transparency, and Conductivity in the Cadmium Indate−Cadmium Stannate System

A novel transparent conducting spinel solid solution Cd1+xIn2-2xSnxO4 (0 ≤ x ≤ 0.75 at 1175 °C) between cubic CdIn2O4 and orthorhombic Cd2SnO4 has been discovered. The extent of this solid solution is noteworthy given that bulk phase relations determined in air over the temperature range 800−1175 °C demonstrate that cubic (spinel) Cd2SnO4 is metastable. Reduced samples exhibit exceptional four-point dc conductivities exceeding 3500 S/cm (x = 0.70). The maximum optical gap estimated from diffuse reflectance spectra is ∼3.0 eV for 0 ≤ x ≤ 0.15. The optical gap shows negligible change with reduction, possibly because of combined Moss−Burstein and band-narrowing effects. Abrupt conductivity increases and optical gap decreases at specific compositions, i.e., x = 0.4 and 0.2 respectively, may be indicative of a change in cation distribution between tetrahedral and octahedral sites. Room temperature thermopower measurements indicate the change in conductivity across the solution is a consequence of an increase i...

Properties of transparent conducting oxides formed from CdO and ZnO alloyed with SnO2 and In2O3

In this article we examine the structural, electrical, and optical properties of several ternary alloy thin films. The alloys are zinc oxide and cadmium oxide, each of which was reacted with both indium oxide and tin oxide to form sputtering targets. The films were deposited by rf sputtering. X-ray diffraction spectroscopy showed that cadmium stannate, cadmium indate, and zinc stannate films were all polycrystalline spinel phase, but only when deposited at room temperature in pure oxygen and then annealed in argon/cadmium sulfide. The fourth alloy, zinc indate, exhibited a hexagonal phase when prepared under identical conditions. Cadmium stannate has one of the lowest resistivities of any transparent conducting oxide (TCO), has low absorbance in the visible spectrum, and is an excellent compromise between electrical and optical requirements. For this material, we show that a single phase is essential for the highest electrical conductivity and lowest optical absorbance. Zinc stannate has a resistivity more than one order of magnitude higher than cadmium stannate but, because of a larger band gap, has an even lower absorbance. We conclude that there is no “best” TCO, and the decision regarding which to use depends on the specific application and the weighting given to electrical versus optical properties. The zinc-bearing alloys are nontoxic, which may also be an attractive feature for many applications.

High Performance Transparent Conducting Films of Cadmium Indate Prepared by Rf sputtering.

AbstractWe are examining various spinel-structured thin films (e.g., Cd2SnO4, Zn2SnO4) to develop higher-quality transparent conducting oxides (TCO) than more conventional materials such as indium tin oxide. Here, we report on cadmium indate (CdIn2O4, CIO), which is another member of this family. Thin films of CIO were deposited by radio-frequency (RF) magnetron sputtering, from an oxide target, onto borosilicate glass substrates. The variables included the substrate temperature, sputtering gas composition, and pressure. Film properties were measured before and after heat treatment. Characterization involved Hall effect measurements, optical and infrared spectrophotometry, X-ray diffraction, and atomic-force microscopy. Film resistivities as low as 2.3x10-4Ω cm were achieved for a film thickness of 0.55 μm. The transmittance was 90% in the visible region of the spectrum, without correction for substrate losses and without an anti-reflection coating. The plasma resonance occurred at longer wavelengths than for other materials and this, with a bandgap of approximately 3.1 eV, presents a wide window for optical transmittance. The highest mobility was 54 cm2 V-s-1 and the highest carrier concentration was 7.5x1020 cm-3.

Transparent conductive CdIn 2O 4 thin films prepared by dc reactive sputtering

Transparent conductive CdIn 2O 4 thin films were prepared by dc reactive sputtering from a CdIn alloy target in an ArO 2 atmosphere. The highest conductivity found for cadmium indate films was 3700 ω −1 cm −1 , ( sheet resistance R ∷ = 5 ω ) with a carrier concentration n of 4×10 20 cm −3 and a mobility μ H of 57 cm 2 V −1 s −1 under optimized technological conditions. The average optical transmission in the visible region of the light spectrum was 90% for 1 μm thick films. All the films prepared contained the cubic spinel phase of CdIn 2O 4 while a secondary phase of In 2O 3 was also present. A carrier scattering mechanism was proposed. The optical band gaps for direct allowed and direct forbidden transitions were derived from the absorption data. The effect of post-deposition heat-treatment in a reducing atmosphere was also investigated.

A spinel form of cadmium stannate

Bulk cadmium stannate, Cd2SnO4, normally crystallizes in the orthorhombic system. Cadmium stannate obtained from sputtered thin films and from a high-temperature, high-pressure procedure has now been shown, on the basis of an X-ray diffraction investigation, to crystallize in the cubic system. The lattice parameter of the face-centered cell is 9.143 ± 0.001 A. The data are consistent with a spinel structure, analogous to cadmium indate.

On the structure of cadmium indate

Abstract The x-ray diffraction powder pattern of CdIn2O4 confirms the structure of this double oxide to be that of a spinel, space group Oh 7–Fd3m, Z = 8, a = 9.166 Å and V = 770.08 Å3. The calculated intensities for normal and inverse distribution are given.