Nanocrystalline chemically modified CdIn2O4 thick films for H2S gas sensor

CdIn₂O₄ sensor with high sensitivity and excellent selectivity for H₂S gas was synthesized by using sol-gel technique. Structural, electrical and gas sensing properties of doped and undoped CdIn₂O₄ thick films were studied. XRD revealed the single-phase polycrystalline nature of the synthesized CdIn₂O₄ nanomaterials. Since the resistance change of a sensing material is the measure of its response, selectivity and sensitivity was found to be enhanced by doping different concentrations of cobalt in CdIn₂O₄ thick films. The sensor exhibits high response and selectivity toward H₂S for 10 wt.% Co doped CdIn₂O₄ thick films. The current-voltage characteristics of 10 wt.% Co doped CdIn₂O₄ calcined at 650 °C shows one order increase in current with change in the bias voltage at an operating temperature of 200 °C for 1000 ppm H₂S gas.     

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

Thin films of the mixed CdO-In₂O₃ 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 In₂O₃ 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 N₂/H₂ gas mixture at 350 °C. X-ray diffraction patterns showed three types of films, excluding those constituted only of CdO and In₂O₃ crystals: i) For X ≤ 50 at.%, the films were constituted of CdO + CdIn₂O₄ crystals, ii) For X = 67 at.%, the films were only formed of CdIn₂O₄ crystals and iii) For X = 84 at.% the films were constituted of In₂O₃ + CdIn₂O₄ crystals. In all films in the 0 < X < 100 range, the formation CdIn₂O₄ crystals of this material was prioritized with respect to the formation of CdO and In₂O₃ 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 In₂O₃), as the X value increases. The resistivity values obtained were in the interval of 8 × 10^− 4 Ω cm to 10⁶ Ω cm. The CdIn₂O₄ films had a resistivity value of 8 × 10^− 3 Ω cm and a band gap value of 3.3 eV.     

Chemical deposition of (311) textured CdIn2S4 thin films

We have successfully deposited cadmium indium sulphide (CdIn₂S₄) thin films by simple dip method using malonic acid as complexing agent. Variation of thickness with time and temperature were studied. Deposited samples were characterized by X-ray diffraction (XRD). The absorption, electrical and photoelectrochemical properties are also studied. The XRD analysis shows that the film samples are in cubic structure. The optical band gap energy was found to be 2.25 eV. Activation energy was found to be 0.511 and 0.018 eV for higher temperature and lower temperature respectively. For CdIn₂S₄ photoelectrode, the open circuit voltage and short circuit current are found to be 125 mV and 86 mA respectively. The calculation shows the fill factor is 33.38 %. The power conversion efficiency is found to be 1.22 %.     

Synthesis and electrochemical properties of nanostructured LiMn2O4 for lithium-ion batteries

Spinel LiMn₂O₄ crystal with the grain sizes of about 15 nm is firstly synthesized by hydrothermal route at 180 °C using MnO₂ as a precursor. The LiMn₂O₄ powders synthesized by hydrothermal technique and sol-gel reaction were investigated by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The LiMn₂O₄ samples were used as cathode materials for lithium-ion battery, whose electrochemical properties were investigated. The results show that the sample obtained by hydrothermal route has higher capacity than that prepared by sol-gel method.     

High sensitivity chlorine gas sensors using CdIn2O4 thick film prepared by co-precipitation method

Gas-sensing properties to dilute Cl₂ have been investigated for CdIn₂O₄ thick film sensors prepared by co-precipitation method. Cadmium nitrate and indium nitrate were mixed in de-ionized water. The 0.1 M NaOH was added to the mixed solution. The co-precipitate obtained was washed, filtered, dried, and calcined at 600-900 °C for 4 h. The CdIn₂O₄ sensor prepared using the powder calcined at 600 °C showed high sensitivity (S=R_g/R_a) to dilute Cl₂ at 250 °C. In particular, the CdIn₂O₄ sensor showed the sensitivity as high as 1200 even to 0.2 ppm Cl₂. The crystal structure and surface morphology were examined by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively.     

Synthesis of nanocrystalline MgAl2O4 spinel powders by a novel chemical method

A novel chemical method for the preparation of nanocrystalline MgAl₂O₄ spinel powders has been developed in this paper. The mixed magnesium-aluminum hydroxide precipitates were initially formed in a three-dimensional space network microarea. After being calcined at above 700 °C, the nanocrystalline MgAl₂O₄ spinel powders were obtained. The precursor and as-calcined powders were characterized using TGA-DTA, XRD and TEM. The MgAl₂O₄ spinel powders calcined at 850 °C for 2 h are of narrow distribution, little agglomeration and small particle size of ∼ 24 nm. The reason for the synthesis of high-quality powders was explained.     

Polymer-assisted synthesis and luminescence properties of MgAl2O4:Tb nanopowder

In the present work, terbium doped magnesium alluminate (MgAl₂O₄:Tb) nanopowder was synthesized by a polyacrylamide gel method. Structure, morphology and luminescence spectra were investigated by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL) measurements. The results showed that the single-phase MgAl₂O₄ could be formed at a relatively low temperature about 800 °C without unreacted Al₂O₃ and MgO phases. Powders with nanosized microstructures were formed. The polyacrylamide gel method resulted in a powder with smaller particle size and fewer agglomerates than the conventional sol-gel method. Luminescence analysis indicated that, the prepared MgAl₂O₄:Tb powders had strong green emission with ⁵D₄-⁷F₅ as the most prominent group. The emission intensity increased with increasing the calcination temperature.     

Optical characterization of BaSm2Ti4O12 thin films by spectroscopic ellipsometry

We performed spectroscopic ellipsometric measurement to characterize BaSm₂Ti₄O₁₂ (BST) thin films grown on Pt/Ti/SiO₂/c-Si substrate by rf magnetron sputtering. The six BST films were prepared at various deposition temperatures and thermal annealing times. The resulting refractive indices and extinction coefficients of the BST films show only slight change by the deposition temperature but a significant change after thermal annealing, implying the importance of the post annealing process. The increase of the refractive index can be understood by the higher density of the BST films caused by the crystallization after annealing process.     

Synthesis of SrAl2O4 from a mixed-metal citrate precursor

A mixed-metal citrate precursor method was used to synthesize SrAl₂O₄. The effects of the pH of the starting solutions and the molar ratio of citric acid to total metal cations concentration (CA/M) on the formation of SrAl₂O₄ were studied. DTA, TG, FT-IR, XRD and field emission scanning electron microscopy (FESEM) were used to characterize the precursors and the derived oxide powders. XRD analysis showed that single-phase SrAl₂O₄ was synthesized from CA/M = 2 precursors at a temperature of 900 °C for 2 h, without the formation of any intermediate phase.     

Syntheses of Mn3O4 and LiMn2O4 nanoparticles by a simple sonochemical method

Mn₃O₄ and LiMn₂O₄ nanoparticles were prepared by a simple sonochemical method which is environmentally benign. First, Mn₃O₄ nanoparticles were prepared by reacting MnCl₂ and NaOH in water at room temperature through a sonochemical method, operated at 20 kHz and 220 W for 20 min. Second, LiOH was coated onto the resulting Mn₃O₄ under the same sonochemical conditions as above. The thickness of coated LiOH on Mn₃O₄ obtained from the reaction ratio of 3:1 between LiOH and Mn₃O₄ was about 4.5–5.5 nm range. Then, by heating those LiOH-coated Mn₃O₄ particles at the relatively low temperature of 300–500 °C for 1 h, they were transformed into phase-pure LiMn₂O₄ nanoparticles of about 50 to 70 nm size in diameter.     

微结构对Bi_2Sr_2Co_2O_y化合物电性能的影响

通过溶胶-凝胶法制备单相Bi2Sr2Co2Oy化合物,通过添加PEG20000和超声分散对化合物粉体微结构进行调控,采用SPS烧结得到了致密的块体.探索了微结构对Bi2Sr2Co2Oy化合物电性能的影响规律.结果表明,添加PEG20000和超声分散可以明显降低Bi2Sr2Co2Oy化合物粉体的晶粒尺寸,使烧结块体的晶粒尺寸大幅度减小,从而显著提高材料的电性能.温度为873K时,添加PEG20000并超声处理所制备样品烧结块体获得了最高ZT值0.041.     

Spray-pyrolysis Cd2SnO4 films for electrochemical applications

Conductive cadmium stannate (Cd₂SnO₄,) films were grown by a simple spray-pyrolysis technique using aerosols ultrasonically generated from solutions containing Cd(thd)₂(TMEDA) and ⁿBu₂Sn(AcAc)₂, and monoglyme as solvent (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate, TMEDA = N,N,N′,N′-tetramethylethylenediamine, AcAc = acethylacetonate). The overall film growing procedure was carried out at or below 400 °C thus allowing low-melting temperature materials like glass to be used as film substrates. Typical resistivity values of Cd₂SnO₄ films were found to be ∼ 2 · 10 ⁻³ Ωcm. The films exhibit excellent electrochemical activity with comparable or higher electron transfer rates than cadmium stannate films obtained via sol-gel methods at high annealing temperature.     

Synthesis of CaCu3Ti4O12 ceramic via a sol-gel method

The novel nano-ultrafine powders for the preparation of CaCu₃Ti₄O₁₂ ceramic were prepared by the sol-gel method and citrate auto-ignition method. The obtained precursor powders were pressed, sintered at 1000 °C to fabricate microcrystal CaCu₃Ti₄O₁₂ ceramic. The microcrystalline phase of CaCu₃Ti₄O₁₂ was confirmed by X-ray powder diffraction (XRD). The morphology and size of the grains of the powders and ceramics under different heat treatments were observed using scanning electron microscopy (SEM). The relative dielectric constant of the ceramic sintered at 1000 °C was measured with a magnitude of more than 10⁴ at room temperature, which was approaching to those of Pb-containing complex perovskite ceramics, and the loss tangent was less than 0.20 in a broad frequency region. The relative dielectric constant and loss tangent were also compared with that of CaCu₃Ti₄O₁₂ ceramic prepared by other reported methods.     

Synthesis of Cu–CdIn2O4 nanoparticles decorated on nickel foam as a sensitive non-enzymatic electrochemical sensor for glucose detection

Fast and effective detection of glucose has important significance in clinical medicine and the diagnosis of diabetes. Electrochemical non-enzymatic glucose sensor has received extensive attention to detect glucose in the recent years due to its simple operation and low cost. In this paper, Cu–CdIn₂O₄ nanoparticles decorated on nickel foam electrode as a sensitive non-enzymatic electrochemical sensor for glucose detection are synthesized by a one-step non-aqueous sol–gel method. Different Cu-doping levels are designed as performance comparison analysis. The electrocatalytic performance of the Cu–CdIn₂O₄ nanoparticles/Ni foam electrodes towards glucose oxidation is evaluated by cyclic voltammetry and current time. The results show that 15% Cu–CdIn₂O₄/Ni foam electrode shows higher sensitivity, as well as an excellent anti-interference and long-term stability towards glucose detection compared with 10% and 20% Cu–CdIn₂O₄/Ni foam electrodes. Hence, 15% Cu–CdIn₂O₄/Ni foam can be regarded as an efficient and a promising sensing material for glucose detection. Such satisfactory performance is not only attributed to the synergistic effect of Cd, In, and Cu, but also benefits from the uniform distribution of 15% Cu–CdIn₂O₄ nanoparticles on the Ni foam, which provides more reactive sites for the electrochemical catalytic reaction.

     

Spray-drying technology for the synthesis of nanosized LiMn2O4 cathode material

Spinel LiMn₂O₄ cathode material has been synthesized by a spray-drying method for lithium ion batteries. During the entire process, the as-prepared powders were characterized using TGA/DTA, XRD, FTIR, SEM and TEM. The results showed that this method not only reduces the sintering time to 5 h at 750 °C, but also decreases the average particle size of LiMn₂O₄ powders to the order of nanometers. The electrochemical performance of nanosized LiMn₂O₄ was investigated by the galvanostatic charge-discharge tests. The data indicate that the nanosized LiMn₂O₄ has a specific capacity of about 130 mA h g^− 1 (1/5 C), and at higher rate (1 C), still has good cycling stability.     

Superconducting YBa2Cu3O7-δ thick films on Ba2RETaO6 (RE = Pr5 Nd, Eu, and Dy) substrates

Thick films of YBa₂Cu₃O_7-δ fabricated on polycrystalline Ba₂RETaO₆ (where RE = Pr, Nd. Eu, and Dy) substrates by dip-coating and partial melting techniques are textured and oaxis oriented, showing predominantly (00/) orientation. All the thick films show a superconducting zero resistance transition of 90 K. SEM studies clearly indicate platelike and needlelike grain growth over a wide area of the thick films. The values of the critical current density for these thick films are ∼10⁴ A/cm² at 77 K as determined by the nonresonant R.F. absorption method. Various processing conditions that affect the critical current density of thick films are also discussed.     

Blue PL and EL emissions from Bi-activated binary oxide thin-film phosphors

The photoluminescent (PL) and electroluminescent (EL) characteristics in the thin films of various Bi-activated binary oxide phosphors have been investigated. La₂O₃:Bi, Gd₂O₃:Bi and Y₂O₃:Bi phosphor thin films were prepared on thick BaTiO₃ ceramic sheet substrates by r.f. magnetron sputtering depositions followed by postannealing. Intense blue PL emissions were observed from all Bi-activated binary oxide phosphor thin films postannealed at a high temperature. Blue, whitish blue-green or blue-green emissions were observed from thin-film electroluminescent (TFEL) devices fabricated with a La₂O₃:Bi, a Gd₂O₃:Bi or a Y₂O₃:Bi thin-film emitting layer, respectively. In addition, high luminance with good color purity in blue EL was obtained in a TFEL device using a La₂O₃:Bi thin film prepared under optimized conditions.     

Enhancement of photocatalysis performance of CdIn2S4/g-C3N4 heterojunction by H2O2 synergism

A highly efficient binary CdIn₂S₄/g-C₃N₄ heterojunction photocatalyst was synthesized by a simple wet impregnation method. Photocatalytic system based on the synergistic action of binary CdIn₂S₄/g-C₃N₄ heterojunction and H₂O₂ was proposed to improve the degradation effect of dyes. The photocatalytic activity was evaluated by the degradation of methyl orange(MO) under visible light irradiation. The results demonstrated that contrasted to pure g-C₃N₄, the synthesized heterojunction can significantly improve the photocatalytic activity. After 120 min of irradiation by visible light, the photocatalytic efficiency of MO degradation of 7CIS/CN was 3.13 times higher than that of g-C₃N₄. When 60 mM H₂O₂ was added on this basis, the photocatalytic efficiency increased from 93.81 to 99.40%. The improvement of photocatalytic activity is attributed to the formation of binary CdIn₂S₄/g-C₃N₄ heterojunction to promote the transfer of photogenerated electron-hole pairs, and an appropriate amount of H₂O₂ as an electron trap further reduced the recombination rate of photogenerated electron-hole pairs. Active species capture experiments showed that ·O₂^? are the main active substances. Subsequently, the mechanism of photocatalytic degradation was proposed. This work provided a new efficient strategy for the degradation of industrial dye wastewater.

     

Flat epitaxial ferromagnetic CoFe2O4 films on buffered Si(001)

Ferromagnetic films of spinel CoFe₂O₄ have been grown epitaxially on Si(001) using CeO₂/YSZ double buffer layers. The heterostructures were built in a single process by pulsed laser deposition with real-time control by reflection high-energy electron diffraction. YSZ and CeO₂ grow cube-on-cube on Si(001) and CoFe₂O₄ grows with (111) out-of-plane orientation, presenting four in-plane crystal domains. The interface with the buffer layers is smooth and the CoFe₂O₄ surface is atomically flat, with roughness below 0.3 nm. The films are ferromagnetic with saturation magnetization around 300 emu/cm³. The properties signal that CoFe₂O₄ is a good candidate for monolithic devices based on ferromagnetic insulating spinels.     

Growth and Characterization of YbBCO Films on Textured Gd2O3 Buffer-Layered Ni Tapes: All Sol–Gel Process

YbBa₂Cu₃O_7–x (YbBCO) thick films were grown on buffered, cube-textured Nickel tapes by sol–gel dip-coating method. Yb-123 films were prepared using solutions of Yb, Ba, and Cu organometallic compounds. A solution-based Gd₂O₃ buffer layer was deposited by dip-coating process with excellent texture and uniformity. The texture development and surface morphology of the buffer-layer films were examined by X-ray diffraction, pole figures, and ESEM analysis. Microstructure and characterization of Yb-123 films were done by ESEM, EDS, and XRD analysis. T _c and J _c were conducted by four-wire measurement method