Amorphous Tin Oxide Research Articles

EXAFS and XANES study of two novel Pd doped Sn/SnOx nanomaterials

EXAFS and XANES at the Pd and Sn K-edges have been used to characterise a novel palladium doped Sn/SnOx nanocomposite that have found application in a new type of high performance solid-state gas sensor. The spherical nanoparticles (10 to 65 nm diameter) prepared either by co-decomposition of Sn and Pd organometallic precursors (doping in volume) or by decomposition of a palladium precursor on preformed Sn/SnOx coreshell nanoparticles (doping in surface) consist of a tin metallic core surrounded by some small platelets of a well-crystallised material embedded in an outer layer of amorphous tin oxide. In this layer tin atoms in an oxidation state close to +IV, are four-fold coordinated to oxygen with bond distances slightly larger than in bulk cassiterite SnO2. In both samples palladium was found to be always in a metallic state, only surrounded by Sn and Pd atoms located at unusually short distances. The two samples that differ mainly by their Pd coordination number present very different morphologies and electrical properties when fully oxidised. A possible location of the Pd atoms in these two materials is proposed.

Electrochemical synthesis and characterization of nanostructured tin oxide for electrochemical redox supercapacitors

Amorphous nanostructured tin oxide (SnO 2) was potentiodynamically deposited onto inexpensive stainless steel (SS) electrode. Potentiodynamic deposition was carried out at a scan rate of 200 mV s −1 from an electrolyte solution of 0.1 M tin dichloride + 0.5 M sodium nitrate + 0.4 M nitric acid. The SnO 2 deposited SS electrodes were characterized by cyclic voltammetry (CV) at various scan rates in 0.1 M Na 2SO 4 for electrochemical redox supercapacitors. A maximum specific capacitance (SC) of 285 F g −1 was obtained from CV at a scan rate of 10 mV s −1. For the same electrode, a SC value of 101 F g −1 was obtained even at a high scan rate of 200 mV s −1, indicating high power characteristics of the material. The SC was found to increase with the increase in specific mass of SnO 2. Long cycle-life and stability of SnO 2 were also demonstrated.

Anodic oxidation of formaldehyde on Pt-modified SnO 2 thin film electrodes prepared by a sol–gel method

Pt-modified SnO 2 electrodes were prepared onto titanium substrates in the form of thin films of ∼2 μm at different temperatures in the range from 200 to 400 °C. Surface morphology was examined by scanning electron microscopy (SEM). It was found that Pt–SnO 2 sol–gel layers are significantly rough and have a low porosity. X-ray diffraction (XRD) studies showed that the films consist of Pt nanoparticles with average size varying from about 5 to 10 nm, depending on the preparation temperature, and amorphous tin oxide. X-ray photoelectron spectroscopy (XPS) was employed to determine the superficial composition of the electrodes and demonstrated the presence of Sn 4+ in all the samples. XPS spectra of the Pt 4f electrons showed the presence of Pt in the zero-valence state as well as in ionic forms. The general electrochemical behavior was characterized by cyclic voltammetry in 1 mol l −1 HClO 4 and the electrocatalytic activity towards the oxidation of formaldehyde was investigated by potential sweeps and chronoamperometry. The results obtained show that the Pt−SnO 2/Ti system exhibits a significant catalytic activity for the oxidation of formaldehyde, with an onset potential below 0.1 V.

Lithium Intercalation into Nanostructured Films Based on Oxides of Tin and Titanium

The lithium intercalation into nanostructured films of mixed tin and titanium oxides is studied. X-ray diffraction and Moessbauer spectroscopy analyses reveal that films consist of a rutile solid solution (Sn, Ti)O2 and an amorphous tin oxide enriched with Sn2+ ions. The films′ specific capacity during the first cathodic polarization in a 1 M lithium imide solution in dioxolane is 200–700 mA h/g, of which nearly one half is the irreversible capacity. During the second cycle, the latter is ∼15% of that in the first cycle. As the films are thin (<1 μm), their capacity does not depend on the current density at 1–80 mA/g. During the electrode cycling, the capacity decreases by 2 mA h/g each cycle. The effective lithium diffusion coefficient, determined by a pulsed galvanostatic method, is ∼ 10–11 cm2/s; it slightly increases with the film lithiation. During the first cycle, the amorphous phase of oxides is reduced to tin metal, the solid solution (Sn, Ti)O2 decomposes, SnO2 disperses to become an x-ray amorphous phase, and TiO2 precipitates as a rutile phase. Lithium reversibly incorporates into the tin metal, yielding Li y Sn, and into a disperse SnO2 phase, yielding Li x SnO2.

Effect of an applied voltage during annealing on the resistivity and transparency of the amorphous tin oxide films

300 nm thick tin oxide thin films were deposited on glass by filtered vacuum arc deposition and annealed in air at 300 and 350 °C for up to 60 min. The resistivity of the coating before annealing was 3 mohm cm. During the annealing, an electric field E in the range of 0–200 V/cm was applied to the sample parallel to the film surface. As the sample was connected in series to a 5 kΩ resistor, the electric field on the sample was not constant during the annealing, depending on the variation of its resistance. The initial magnitude of the electric field on the sample was in the range of 0–17.4 V/cm. Film resistance decreased as function of short annealing times, reaching a minimum value after 1 to 3 min, and depended on the applied voltage U. At longer annealing times, the resistance continuously increased up to saturation after 8 min. The magnitude of the saturated resistance also depended on U, that is, on the field in the sample. The lowest electric resistivity (0.6 mohm cm) was obtained at 300 °C and U=100 V (initial field in sample of ∼9 V/cm). The minimum resistivity of annealed films without electric-field application was three times higher, 1.8 mohm cm. However, the minimal resistivity measured when U=200 V/cm (initial field 19.4 V/cm) was 2.1 mohm cm, i.e., larger by a factor of ∼1.2 than that obtained with no field. The visible transmittance, T, was measured before and after annealing, being 67% before annealing. The transmittance of annealed films depended on the annealing time and the applied field. The highest visible transmittance of films annealed with E=100 V/cm was 89%, and obtained after annealing for 5 min. The maximal visibility of films annealed with no field was 81%, and obtained after annealing for 8 min. The atomic ratio O/Sn on the film surface decreased linearly with time from ∼2 to ∼0.7 with U=100 V, but it remained greater than 1.3 at U=0 V. The O/Sn ratio remained approximately constant (∼2) at a depth larger than 20 nm.

Effect of orthorhombic phase on hydrogen gas sensing property of thick-film sensors fabricated by nanophase tin dioxide

Nanophase metallic tin powder was synthesized by an inert gas condensation method and subsequently oxidized into two types of SnO 2 by two heat-treatment routes: (1) after annealing up to 900 °C in air, the synthesized powder was oxidized to form a mixture of tetragonal and orthorhombic SnO 2, and (2) the synthesized powder was transformed into an amorphous tin oxide by intermediate annealing at 225 °C. The amorphous tin nano-particles were oxidized into a single phase of tetragonal SnO 2 during heat treatment up to 900 °C in air. The sensitivity of the sensors fabricated from two types of nanophase SnO 2 powders was evaluated by means of electrical resistance measurements. The thick-film sensors fabricated by the mixed SnO 2 powder exhibited a lower sensitivity to hydrogen than those fabricated by the single tetragonal SnO 2 powder. TEM observations and EPR measurements were carried out in order to interpret the role of the orthorhombic phase in gas sensing. The detrimental effect of orthorhombic SnO 2 on the sensitivity was attributed to an increased number of planar defects in the microstructure and a change in species of oxygen absorbents on the surface layer of the SnO 2.

Effect of air annealing on opto-electrical properties of amorphous tin oxide films

Amorphous tin oxide films, 100–800 nm thick and of resistivity ∼6–8 mΩ cm, were deposited on glass substrates using a filtered vacuum arc with an oxygen background gas pressure of 4.0 mTorr. The films were annealed in air at a temperature of 300°C for 1, 3, 5, 7, and 10 min. Film morphology, structure, composition, roughness, and light transmission were determined before and after the annealing, on cold samples, with atomic force microscopy, x-ray diffraction diagnostics, x-ray photoelectron spectroscopy, and light transmission meter. The roughness depended weakly on the annealing time, and decreased with the thickness of the film. The film transmission in the visible region was practically independent of the annealing time. Film conductivity increased with the annealing time, reaching a maximum value after 3–7 min, larger by a factor of 2.0–2.9 than that measured before annealing. The oxygen to tin density ratio on the film surface decreased relative to its value before annealing and reached a minimum after annealing for 7 min. After annealing for 10 min, the O/Sn ratio increased relative to the minimum value but was lower than the ratio before annealing. The O/Sn ratio in the bulk decreased monotonically for annealing times longer than 1 min. The film conductivity before and after annealing depended linearly on the film thickness. A model is proposed to elucidate the dependence of the conductivity on the annealing time and on the film thickness.

Process of crystallization in thin amorphous tin oxide film

Amorphous tin oxide films deposited on carbon substrates have been studied by high-resolution transmission electron microscopy. As-deposited film was composed of a mixture of microcrystallites of SnO, SnO 2 and SnO 3 with size of 2 nm. Crystallization took place above 450°C. SnO crystals appeared between 450°C and 500°C, whereas SnO 2 crystals appeared above 550°C. The appearance of β-tin crystals with the reduction of tin oxide has been verified using the heating stage of the electron microscope. A drop of liquid tin was recognized upon heating above 500°C. The difference in crystallization upon applying an electron beam, synchrotron radiation and heating in vacuum has been summarized and discussed with respect to the problem of the excitation of crystallites.

Sn 산화물 나노입자 형성에 미치는 대류 가스의 영향

In the present study of IGC (Inert Gas Condensation) evaporation-condensation processing study, the effects of IGC convection gas on the crystallographic structure, size and shape of tin oxide nanoparticles were investigated. In addition, the phase transformation of tin oxide nanoparticles was studied after heat treatment. IGC processing was conducted at 1000℃ for 1 hr. The mixture gas of oxygen and helium was used as a convection gas. Metastable tetragonal SnO nanoparticles were obtained at a lower convection gas pressure, whereas amorphous tin oxide nanoparticles were obtained at a higher one. The formation of amorphous phase could be explained by the rapid quenching of the vaporized atoms. The resultant nanoparticles size was about 10 nm with a rounded shape. The tin oxide nanoparticles prepared by IGC were almost transformed to the stable tetragonal SnO₂ after heat treatment.

Effects of Amorphous Carbon Films on the Performance of Porous Silicon Electroluminescence

ABSTRACTEfficient electroluminescence (EL) is obtained at low operating voltages (&lt;3 V) from n+-type silicon- electrochemically oxidized thin nanocrystalline porous silicon (PS)-amorphous carbon-Indium tin oxide (ITO) junctions. The effects of a few nanometer thick amorphous carbon film between PS and ITO on the EL characteristics have been investigated. The carbon film enhances the stability. The EL efficiency is improved due to a reduction of current density and an increase in EL intensity. In addition, the reproducibility from device to device is very much improved by the carbon film. The enhancement in stability should originate from the capping of PS by the carbon film and the high chemical stability of carbon and Si-C bonds, which should prevent PS oxidation. The carbon film acts as an efficient buffer layer between PS and ITO, resulting in enhanced mechanical, electrical and chemical stability of the top contact and providing high reproducibility. The thin carbon film has only positive effects on all the EL characteristics. This is a very important step towards application.

Electrochemical treatment of toxic compounds on the surface of amorphous Ni–Nb–Pt–Sn alloys

Acid aqueous solutions of phenol, hydroquinone, and p-benzoquinone have been treated by electrochemical methods to obtain the oxidation of these toxic compounds to CO 2 and water. The electrochemical reaction was occurred at the surface of different Ni–Nb–Pt–Sn alloys. The properties of the electrodes shows that the electrochemical oxidation occurs at Pt in the amorphous state and tin oxide layers that are supported in a nickel–niobium matrix. The results show that the optimum composition is Ni–40Nb–0.6Pt–0.4Sn (at.%) and 36% phenol, 29% hydroquinone and 23% of benzoquinone are reduced to CO 2 and H 2O after 3 h of electrochemical oxidation in conditions of 100 A m −2 . The synergistic effect of Sn and Pt as metallic particles is demonstrated by these results.

Effect of SR irradiation on crystallization of amorphous tin oxide film

In order to see the effect of SR irradiation on crystal growth, crystallization of tin oxide films has been performed in vacuum under SR irradiation. A thin amorphous tin oxide film 50 nm thick was prepared on the carbon substrate by vacuum evaporation of SnO 2 power. A SnO crystal appeared between 450–500°C upon vacuum heating, with a preferred orientation of (0 0 1). By SR irradiation using a cylindrical mirror for 20 s, the SnO crystal appeared with the preferred orientation of (1 1 1). The crystal with the crystallographic shear structure was grown by SR irradiation. This growth under a SR beam is discussed in terms of SR beam excitation of lone-pair electrons seen in the SnO crystal structure.

Preparation of mixed oxide MoO 3–WO 3 thin films by spray pyrolysis technique and their characterisation

Mixed oxide MoO 3–WO 3 thin films have been deposited onto the amorphous and fluorine doped tin oxide (FTO) coated glass substrates at 300°C by using a simple and inexpensive spray pyrolysis technique. Equimolar ammonium tungstate and ammonium molybdate solutions were mixed together in volume proportions and used as precursors for spraying. The samples were annealed at 400°C for 1 h. They were approximately 0.6 μm thick. The structural, electrical and optical properties were studied and values of room temperature electrical resistivity, its activation energy and band gap energy were estimated. The crystallinity of the samples improved with increase in Mo content in the samples. The sample with 2% Mo-oxide in the W-oxide sample exhibited more pronounced electrochromism than other samples including WO 3. The existence of two peaks in the cyclic voltammogram, unlike WO 3, suggests that there are two kinds of oxidation states corresponding to WO 3 and MoO 3. The response times were also improved when Mo oxide is added into the WO 3. The stability of these samples were tested by repeating colour/bleach cycles several times in H 2SO 4 electrolyte.

中国後漢代青銅鏡の土中腐食層内で観察された結晶学的特異現象

Recently, we have got a chance to collect a small piece of the ancient bronze mirror, which had been manufactured in the middle or the late Chinese Han period. To investigate it’s metallurgical properties by means of optical microstructure observation and various instrumental analyses. From these investigations, we have detected the crystalline anomalies in the corroded layer alias “bronze disease” layer in the clay for the ancient bronze mirror. Results obtained were as follows:(1) The apparent density of the mirror, measured by means of the Archimedes method, tends to decrease with the extent of the corroded layer in the clay.(2) The semi-transparent thin film formed on the mirror was the crystalline tin oxide (SnO2).(3) The corroded structural defect alias “bronze disease” layer formed just under the surface of mirror was the amorphous (like) tin oxide, which contains lower Cu and higher Pb contents.(4) Mechanisms of the formations of the semi transparent thin film on the mirror surface and the amorphous (like) layer in the attacked layer in the clay and the behavior of the copper element should be made clear hereafter.

Amorphous tin oxide films: preparation and characterization as an anode active material for lithium ion batteries

Tin oxide thin films were prepared by the electrostatic spray deposition at 400°C, followed by annealing at 500°C in air. X-ray diffraction and X-ray photoelectron spectroscopy revealed that the resulting films were amorphous SnO 2. The electrochemical properties of the SnO 2 films with lithium were studied by in situ conductivity measurements using an interdigitated microarray electrode as well as by cyclic voltammetry, galvanostatic cycling measurements and ac-impedance spectroscopy in 1 M LiClO 4/(PC+EC). The SnO 2 film electrodes exhibited reversible capacities greater than 1300 mA h g −1 when cycled between 0.05 and 2.5 V at 0.2 mA cm −2. However, this capacity faded rapidly after repeated cycling. If the electrode was cycled between 0 and 1.0 V, a reversible capacity of 600 mA h g −1 was maintained for more than 100 cycles. In addition, a stable reversible capacity of about 500 mA h g −1 was obtained even at current density as high as 2 mA cm −2. Thus it is suggested that a higher potential than 1.5 V would cause reformation of tin oxide, which may destroy the stable nanocomposite structure of metallic tin and lithium. These arguments were supported by in situ conductivity measurements with microarray electrodes.

Structure and chemical characteristics of tin oxide films prepared by reactive-ion-assisted deposition as a function of oxygen ion beam energy

Tin oxide films were deposited on amorphous SiO2/Si and Si (100) substrates by ion-assisted deposition (IAD) at various ion beam potentials (VI) at room temperature and a working pressure of 8 × 10−5 torr. The structural and chemical properties of the as-grown tin oxide films were investigated to determine the effects of the oxygen ion/atom arrival ratio (Ri). X-ray diffraction patterns indicated that the as-grown films with different average energy per atom (Eave) showed different growth directions. The as-grown films with oxygen/Sn ratio (NO/NSn) of 2.03 and 2.02 had preferred orientation of (101) and (002), respectively. In addition, the as-grown film with low Ri was amorphous. Comparison of the observed d spacings with those for standard SnO2 samples, indicated that the crystalline as-grown films had compressive and tensile stress depending on Eave. In transmission electron microscopy analysis, a buffer layer of amorphous tin oxide was observed at the interface between the substrate and the film, and the crystalline grains were grown on this buffer layer. The crystalline grains were arranged in large spherical clusters, and this shape directly affected surface roughness. Rutherford backscattering spectroscopy spectra showed that the tin oxide thin films were inhomogeneous. The density of films decreased and the porosity and oxygen trapped in the films increased with increasing Ri. The densest film had about 6% porosity.

00/02647 Thermal and electrochemical studies of carbons for Li-ion batteries. 2. Correlation of active sites and irreversible capacity loss

Amorphous tin-oxide films were prepared by spray pyrolysis of SnCl2·2H2O mixed with CH3–COOH and deposited onto a stainless steel substrate at mild temperatures (350°C). The films grown were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). Also, they were tested as electrodes in lithium rechargeable batteries. The XPS results suggest that the substrate is thoroughly coated and that the films are composed mainly of SnO and SnO2. These films exhibit good charge–discharge properties over more than 100 cycles. Heating at 600°C causes significant changes in their surface composition, in the virtual disappearance of the tin component and in the presence of oxygen-bound Fe. Under these conditions, the reversible capacity dramatically fades and the cell behaves similarly to that made from uncoated substrate.

00/02649 Use of amorphous tin-oxide films obtained by spray pyrolysis as electrodes in lithium batteries

00/02649 Use of amorphous tin-oxide films obtained by spray pyrolysis as electrodes in lithium batteries

Characterization of tin oxide/LiMn 2O 4 thin-film cell

An amorphous, thin film of tin oxide is tested as an anode to replace lithium metal in a thin-film battery. Tin oxide shows irreversible discharge capacity in its initial state, and this gives rise to capacity loss on the first charge–discharge process. Thus, in terms of electrochemical properties, lithium metal is better than tin oxide as an anode for a thin-film battery. In some applications, however, thin-film batteries must withstand high fabrication temperatures (over 250°C to 260°C). Lithium metal film cannot be applied in such conditions due to its low melting point (181°C). Tin oxide is not only able to endure high fabrication temperatures but can also preserve its capacity for a large number of cycles after the initial discharge process. In this study, a thin film of amorphous tin oxide has been prepared by means of a sputtering method. Its suitability as an anode for a thin-film battery is examined. A thin film of LiMn 2O 4, prepared by a sol–gel method is used for the cathode.

Use of amorphous tin-oxide films obtained by spray pyrolysis as electrodes in lithium batteries

Amorphous tin-oxide films were prepared by spray pyrolysis of SnCl 2·2H 2O mixed with CH 3–COOH and deposited onto a stainless steel substrate at mild temperatures (350°C). The films grown were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). Also, they were tested as electrodes in lithium rechargeable batteries. The XPS results suggest that the substrate is thoroughly coated and that the films are composed mainly of SnO and SnO 2. These films exhibit good charge–discharge properties over more than 100 cycles. Heating at 600°C causes significant changes in their surface composition, in the virtual disappearance of the tin component and in the presence of oxygen-bound Fe. Under these conditions, the reversible capacity dramatically fades and the cell behaves similarly to that made from uncoated substrate.