Tin Oxide Phases Research Articles

Enhanced photocatalytic activity of Co doped SnO2 nanoparticles by controlling the oxygen vacancy states

Abstract Co doped SnO2 nanoparticles were synthesized by chemical precipitation. Excess Co ions as doping element were used to compensate the deficit of oxygen from SnO2 lattice. The crystalline structure of all samples corresponds to tetragonal rutile crystalline phases of tin oxide and the crystallinity increases by doping. The nanoparticles shape is polyhedral with narrow distribution. The presence of Co ions in SnO2 lattice results in decreasing the oxygen deficiency. All the doped samples show the red shift in optical response. Photoluminescence emission spectra show peaks in UV and visible region. Visible emissions decrease by doping which indicate lower recombination rate of photogenerated electron-hole pairs. All the samples show photocatalytic activity against RhB synthetic solution under visible light irradiation, the best performance was obtained using 1.0%Co–SnO2. The mechanism of photocatalytic activity was explained based on the reactive oxygen species generated by nanoparticles under visible irradiation in correlation with structural and optical information obtained in this study.

Remarkable Electrical Conductivity Enhancement Through Mutual Variation of MWCNTs/Tin Oxide Concentration: Structural, Morphological and Electrical Properties

Tin oxide/MWCNTs hybrid nanocomposites were synthesized via the malic acid-assisted modified sol–gel method. Effect of the concentration variation of both MWCNTs and tin oxide on the hybrid nanostructure, morphology, thermal and optical properties was studied using spectroscopic and analytical tools including: thermal gravimetric analyses (TGA), x-ray diffraction (XRD), scanning electron microscope (SEM), transition electron microscope (TEM), and ultraviolet–visible (UV–Vis) spectroscopy. Thermal gravimetric analyses of the hybrid nanocomposites showed a mode of stability up ≈ 375°C, after this temperature the sample is subjected to decomposition of the MWCNTs. XRD patterns of the pristine tin oxide sample showed the presence of characteristic peaks related to two crystalline phases of tin oxide (rutile SnO2 and orthorhombic SnO), while the hybrid CSn10 (synthesized via 10% weight substitution of MWCNTs by tin oxide) and SnC10 (synthesized via 10% weight substitution of tin oxide by MWCNTs) nanocomposites showed a clear decrease in the crystallinity as a proof for dispersing of tin oxide nanoparticles within the hollow cavity of MWCNTs, which was further confirmed by SEM and TEM images. Furthermore, a complete absence of the characteristic peak of orthorhombic SnO was observed in the CSn10 sample. Optical and electrical properties of the hybrid nanocomposites-chitosan thin films were investigated before and after exposing to UV radiation for 1 h. The UV–Vis spectra showed a blue shift upon introducing MWCNTs into the oxide matrix while prolonged exposure to UV-radiation markedly affected the absorption and the band gaps of all nanocomposites. Investigation of the electric properties interestingly showed remarkable electrical conductivity enhancements upon introducing either MWCNTs or tin oxide in the matrix of each other. Introducing 10% MWCNTs into the tin oxide structure (SnC10) was accompanied by 76-fold increase in the electric conductivity; while incorporating 10% of tin oxide (CSn10) was accompanied by 110-fold increase in the electric conductivity of MWCNTs at 100 Hz frequency. Furthermore, the effect of prolonged UV-radiation on the electric properties of the synthesized hybrid nanocomposites was also reported.

A multidisciplinary non-destructive study of historical pipe organ fragments

A multidisciplinary non-destructive study has been carried out on historical pipe organ fragments, trying to infer whether the spatial occurrence of different crystallographic phases (that is alpha‑tin, beta‑tin, cassiterite or romarchite) reflects the visible alterations patterns. We could indeed derive the presence of the beta‑tin phase. Several tin oxide phases have been detected too, associated with the visible occurrence of “grey regions” and hole borders (mapped by Raman spectroscopy), and hydrate phases (mapped by neutron imaging).We aim to demonstrate that neutron and Raman techniques can give relevant indications in archaeometallurgy studies of cultural heritage artifacts, where only non-destructive experiments can be performed. The combination of the two probes could be considered a protocol to be applied in the characterization of tin based specimens.

Growth and surface structural study of tin oxide films on Ag(001)

Tin oxide was prepared by reactive deposition of Sn in an O2 atmosphere at both room temperature (RT) and high temperature (HT) at 573 K as well from one monolayer to ten monolayer film coverages. The grown films were studied at RT by a combination of x-ray photoemission spectroscopy (XPS), low energy electron diffraction (LEED) and ultraviolet photoemission spectroscopy (UPS). At RT, the coexistence of both SnO and SnO2 was confirmed by XPS and valence band data with more SnO being formed at higher coverage. However, only one oxidised phase of tin oxide mainly due to SnO2 was formed at HT for most of the coverage. Presence of SnO was also confirmed only at the highest coverage studied here for HT. A multidomain LEED pattern having square (1 × 1) domains at 30° to each other was reported for low coverage of tin oxide at RT, which with an increase in coverage, gives rise to diffused background confirming no ordered tin oxide was formed. The similar multidomain structure was also noticed for HT growth from lower coverage up to 5 monolayer equivalent (MLE) coverage which then transformed into hexagonal multidomain LEED pattern for higher coverage confirming the presence of clear oxide phase, unlike the RT growth case.

Designing a Sn-slag composite with possible non-toxic applications to provide a pure metal casting environment

Foundry slag formed during the production of medium carbon steel was milled into powder which was then compacted into blocks to form heat treatment furnace refractory materials. The foundry slag was ball-milled into powders which were further heat-treated at 300, 400, 500, 600 and 700 °C for 1 h. XRD pattern of ball-milled and heat-treated slag powder showed the rhombohedral and face-centred cubic (FCC) eta-phase. The dominating phase detected through the XRD is the α-Al2O3 with a rhombohedral crystal structure. The corresponding lattice parameters for therhombohedral crystal structure are a = 0.476 nm; c = 0.129 nm with R-3c # 167 space group and number. The density of the milled slag was measured at 3.325 ± 0.085 g/cm3, which is lower than pure alumina (3.69 g/cm3). After mixing the slag powder with Sn, a good microstructural bonding yielding alumina and tin oxide phases formed after sintering. Recycling of the waste foundry slag into a usable product provides an opportunity not only for value addition but eliviates the burden of slag disposal to preserve the environment.

Synthesis and characterization of three-dimensional flower-like tin dioxide-based structures

Three-dimensional flower-like SnO2-based structures have been produced by the alkaline hydrothermal treatment of t-SnO2 powder with no additive and in the presence of aminoterephthalic acid (ATPA). The synthesis products have been characterized by a variety of physicochemical techniques (scanning electron microscopy, transmission electron microscopy, Raman and IR spectroscopies, X-ray diffraction, and others). The results demonstrate that raising the ATPA concentration in the reaction mixture changes the morphology of the materials and leads to the SnO2 → SnO2/Sn3O4 → Sn3O4 phase transformation in the structures through the formation of SnO x nonstoichiometric tin oxide phases with 1 < x < 2. Hydrothermal treatment of the starting reagents in the presence of ≤75 wt % ATPA leads to the formation of hierarchical structures dominated by a nonstoichiometric tin oxide, which is thermally unstable at t ≥ 500°C. The morphology and phase composition of the synthesized structures have been shown to have a significant effect on the electronic conductivity of the material.

Static and Dynamic Disorder in Metastable Phases of Tin Oxide

The multistage transformation of Sn3O4 to SnO2 in an oxygen-free atmosphere has been studied using hydrothermally synthesized samples, both pristine and heated, with in situ X-ray diffractometry, Raman spectroscopy, differential scanning calorimetry, dielectric spectroscopy, and ex situ X-ray photoelectron and nuclear magnetic resonance spectroscopies. Experimental evidence consistently shows that, beginning from 250 °C, Sn3O4 converts to Sn2O3 and, from 350 °C, to SnO2, accompanied by the formation of metallic tin. These two stages are associated with frequency-dependent dielectric losses, as revealed by impedance measurements, which also indicate a significant conductivity of 1.78 eV in activation energy. It is speculated that the relaxation-like processes relate to the transition from static to dynamic disorder and then to order in the oxygen sublattice.

Structural, morphological, optical and electrical properties of Sb-doped SnO2 thin films obtained by aerosol assisted chemical vapor deposition

In this work, we report the synthesis and characterization of antimony doped tin oxide thin films for their possible application as transparent conducting oxides. Thin films of antimony doped tin oxide were deposited by aerosol assisted chemical vapor deposition. Surface morphology and microstructure were studied by field emission scanning electron microscopy. X-ray diffraction results indicate the presence of two tin oxide phases in some samples (from thickness of 30–120nm) and only the cassiterite phase in samples with thicknesses greater than of 140nm. Optical properties of the samples were analyzed by total transmittance spectra. Resistivity of the films was obtained by the sheet resistance method. Electrical properties and conductivity type of samples were determined by Hall effect method. The results show low resistivity in antimony doped tin oxide materials decreasing up to six orders of magnitude compared to pure tin oxide, and obtaining resistivity in the order of magnitude of 10−4Ω·cm. Thermal treatment was performed on some materials and stability was observed because it did not decrease its resistivity and in addition the thermal treatment improved Hall mobility.

Demonstration of high-performance p-type tin oxide thin-film transistors using argon-plasma surface treatments

In this work, we investigated the effects of low-temperature argon (Ar)-plasma surface treatments on the physical and chemical structures of p-type tin oxide thin-films and the electrical performance of p-type tin oxide thin-film transistors (TFTs). From the x-ray photoelectron spectroscopy measurement, we found that SnO was the dominant phase in the deposited tin oxide thin-film, and the Ar-plasma treatment partially transformed the tin oxide phase from SnO to SnO2 by oxidation. The resistivity of the tin oxide thin-film increased with the plasma-treatment time because of the reduced hole concentration. In addition, the root-mean-square roughness of the tin oxide thin-film decreased as the plasma-treatment time increased. The p-type oxide TFT with an Ar-plasma-treated tin oxide thin-film exhibited excellent electrical performance with a high current on–off ratio (5.2 × 106) and a low off-current (1.2 × 10−12 A), which demonstrates that the low-temperature Ar-plasma treatment is a simple and effective method for improving the electrical performance of p-type tin oxide TFTs.

Raman studies of the intermediate tin-oxide phase

The existence of an intermediate phase of tin oxide was first reported in 1882. However, its stoichiometry and its crystal structure have been dubious and heavily debated ever since, despite a multitude of structural investigations. We show that Raman spectroscopy combined with ab initio theory offers a viable alternative for structure determination in cases where diffraction studies are inconclusive. We unambiguously identify the intermediate phase as ${\mathrm{Sn}}_{3}{\mathrm{O}}_{4}$ and rule out the other likely candidate, ${\mathrm{Sn}}_{2}{\mathrm{O}}_{3}$. We assign the one-phonon Raman signals of ${\mathrm{Sn}}_{3}{\mathrm{O}}_{4}$ to the mode symmetries of the corresponding point group ${C}_{2h}$ and confirm that $P{2}_{1}/c$ with 14 atoms per unit cell is the space group of ${\mathrm{Sn}}_{3}{\mathrm{O}}_{4}$.

Erratum to: Effect of ageing on Sn6O4(OH)4 in aqueous medium—simultaneous production of SnO and SnO2 nanoparticles at room temperature

Precipitation is one of the dominant techniques for producing tin oxide which requires calcination of the interim tin oxide hydroxide (Sn6O4(OH)4) precipitate at different temperatures to render the requisite oxide states. In this study, we mitigated the necessity for calcination through simple ageing of the the as-synthesized Sn6O4(OH)4 at room temperature (25 °C) in aqueous medium. Ageing for 12 days resulted in phase transition of the interim precipitate and production of discernible layers of black stannous oxide (SnO) and yellow stannic oxide (SnO2) along with the originally formed white layer of Sn6O4(OH)4 within the same aqueous medium. The phases of tin oxide was confirmed after extracting individual layer and assessing them through X-ray analysis. Thermogravimetric analysis for the as-obtained stannous oxide established its thermal stability up to around 410 °C. Additionally, Field Emission Scanning Electron Microscopy studies performed on the SnO nanoparticles revealed their dimension to be within 25–30 nm range. The mechanisms for SnO and SnO2 formation through ageing has been delineated.

Comparative analysis of physico-chemical and gas sensing characteristics of two different forms of SnO2 films

In this paper the results of studies of comparative studies on the crystallinity, morphology and chemistry combined with the gas sensor response of two different forms of tin dioxide (SnO2) films prepared by the Rheotaxial Growth and Thermal Oxidation (RGTO) and by the Laser-enhanced Chemical Vapour Deposition (L-CVD) methods, respectively, are presented.For this purpose the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Photoelectron spectroscopy (XPS) have been used. XRD studies for both samples show the contribution from the crystalline SnO2 in the cassiterite rutile phase without any evident contribution from the tin oxide (SnO) phase. SEM and AFM studies show that the surface morphology of RGTO and L-CVD SnO2 samples are characterized by grains/nanograins of different size and surface roughness.In turn XPS studies confirm that for both SnO2 samples a slight nonstoichiometry with a relative [O]/[Sn] concentration of 1.8, and slightly different amount of C contamination at the surface of internal grains with relative [C]/[Sn] concentration of 3.5 and 3.2, respectively. This undesired C contamination cannot be ignored because it creates an uncontrolled barrier for the potential gas adsorption at the internal surface of sensor material. This is confirmed by the gas sensor response in NO2 atmosphere of both SnO2 samples because the sensitivity is evidently smaller for RGTO SnO2 with respect to the L-CVD SnO2 samples, whereas the response time showed a completely opposite tendency. It is probably caused by the smaller extension of internal surface and grain dimension with respect to the Debye length, as well as higher C contamination observed for RGTO SnO2 with respect to L-CVD SnO2 samples.

Synthesis and Microstructural Characterization of SnO2:F Thin Films Deposited by AACVD

In this work, we report the synthesis and microstructural characterization of Tin oxide thin films doped with fluorine for applications such as transparent conductive oxides. Tin oxide doped with fluorine thin films were deposited by aerosol assisted chemical vapor deposition technique onto a borosilicate glass substrate, using a precursor solution of stannic chloride in ethanol and ammonium fluoride as the dopant. Deposition temperature was varied between 623-773 K. Also, other deposition parameters such as concentration of the precursor solution and gas carrier flux were fixed at 0.1 mol∙dm-3 and 5 L min-1 respectively. Results indicate the presence of only the cassiterite phase of Tin oxide in all samples. Thin films obtained were characterized by X-Ray Diffraction. Surface morphology and microstructure were studied by field emission scanning electron microscopy, optical properties of samples were analyzed by total transmittance and reflectance spectra. The resistivity value of the films was measured by the sheet resistance.

Morphology and phase transformations of tin oxide nanostructures synthesized by the hydrothermal method in the presence of dicarboxylic acids

A new approach to the synthesis of non-stoichiometric tin oxide structures with different morphologies and the phase compositions has been evaluated. The nanostructures were synthesized by hydrothermal treatment of the mixtures of dicarboxylic acids ― aminoterephthalic or oxalic ― with nanocrystalline SnO2 powder, which was obtained via the sol-gel technology. The products were characterized by Raman and IR spectroscopy, SEM, HRTEM, and XRD analysis. It was shown that the controlled addition of a dicarboxylic acid leads not only to a change in the morphology of the nanostructures, but also to SnO2–SnO2/Sn3O4–Sn3O4–SnO phase transformations. A single-phase Sn3O4 in the form of the well-separated hexagonal nanoplates and mixed SnO2/Sn3O4 phases in the form of hierarchical flower-like structures were obtained in the presence of organic additives. The effects of concentration, redox activity of the acids and heat treatment on the basic characteristics of the synthesized tin oxide nanostructures and phase transformations in the synthesized materials are discussed.

Structural, photoconductive, thermoelectric and activation energy measurements of V-doped transparent conductive SnO2 films fabricated by spray pyrolysis technique

This report investigated the structural, optical and electrical properties of V-doped SnO2 thin films deposited using spray pyrolysis technique. The SnO2:V films, with different V-content, were deposited on glass substrates at a substrate temperature of 550°C using an aqueous ethanol solution consisting of tin and vanadium chloride. X-ray diffraction studies showed that the SnO2:V films were polycrystalline only with tin oxide phases and the preferred orientations are along (1 1 0), (1 0 1), (2 1 1) and (3 0 1) planes. Using Scherrer formula, the grain sizes were estimated to be within the range of 25–36 nm. The variation in sheet resistance and optical direct band gap are functions of vanadium doping concentration. Field emission scanning electron microscopy (FESEM) revealed the surface morphology to be very smooth, yet grainy in nature. Optical transmittance spectra of the films showed high transparency of about ∼69–90% in the visible region, decreasing with increase in V-doping. The direct band gap for undoped SnO2 films was found to be 3.53 eV, while for higher V-doped films it shifted toward lower energies in the range of 3.27–3.53 eV and then increased again to 3.5 eV. The Hall effect and Seebeck studies revealed that the films exhibit n-type conductivity. The thermal activation energy, Seebeck coefficient and maximum of photosensitivity in the films were found to be in the range of 0.02–0.82 eV (in the low-temperature range), 0.15–0.18 mV K−1 (at T = 350 K) and 0.96–2.84, respectively.

Fabrication and phase characterization study of SnS thin films under controlled sulfur deposition temperature

SnS thin films were prepared from the multilayer of Sn and S using vacuum and atmospheric (atm) pressure thermal evaporation methods respectively, followed by vacuum annealing process at 360°C for 1.5 hour. For the multilayer, sulphur layer was deposited at 175°Cand 200°C 5 hr and 250°C for 2.5hr duration from alumina crucible under standard atm condition, whereas Sn film of thickness 10nm was coated alternatively under 1E-5 mbar using thermal evaporation method. XRD studies shows that at low sulfurization temperature (Ts) of 175°C Sn and Sn2S3 is present because of the low formation energy of Sn2S3 than SnS and by increasing Ts to 200°C SnS phase is formed confirm from XRD, with decreasing the intensity of Sn peaks which indicates that this temperature could accelerate the formation of SnS phase. Raman analysis also confirms the formation SnSphase(95±2, 190±2,218±2, 164±2, 290±4 cm-1) along with Sn2S3 (58 and 307 cm-1) and Sn phases (125cm-1). Raman analysis shows that the relative intensity (RI) (%) of Sn decreases and RI (%) of SnS increases systematically by increasing Ts. Importantly, the formation of tin oxide phases is not observed under any of these conditions as confirmed by Raman and XRD analysis. The mean particle size increases from 33nm (Sn) to 97nm (SnS) after sulfurization process as corroborated by AFM. The absorbance spectra clearly indicate a significant change in the absorbance by varying Ts. A broad absorption arises due to Sn in samples S1 and S4 which disappears in S2 and S3 due to formation of SnS phase, confirmed by Raman and XRD analysis.

Thermoanalytical study of precursors for tin sulfide thin films deposited by chemical spray pyrolysis

Thermal decomposition of precursors for SnS thin films obtained by drying aqueous solutions of SnCl2 and SC(NH2)2 in the Sn:S molar ratios of 1:1 (1) and 1:8 (2) was monitored by simultaneous thermogravimetry/differential thermal analysis (TG/DTA) measurements in the dynamic 80 % Ar + 20 % O2 atmosphere. The evolved gaseous species from 1 were recorded by simultaneous thermogravimetry/differential thermal analysis/evolved gas analysis–mass spectrometry (TG/DTA/EGA-MS) measurements. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the dried precursors and products of the thermal decomposition. The precursor 1 is a complex compound, Sn(tu)Cl2, while 2 consists of Sn2(tu)5Cl4·H2O and noncomplexed thiourea. The thermal degradation of 1 and 2 in the temperature range of 30–700 °C consists of four steps with a total mass loss of 68.0 and 84.5 %, respectively. According to XRD, the solid decomposition products at 210 °C of 1 are SnS2, (NH4)2SnCl6 and C(NH2)3SnCl3, and of 2 are SnS2, SnS, NH4Cl and (NH4)2SnCl6. Decomposition of 1 and 2 is completed by 550 and 570 °C, respectively. The final decomposition product of 1 and 2 at 700 °C is SnO2. This study shows that the excess of thiourea in the spray solution, compared to that required for the formation of the intermediate tin complex compounds, suppresses the formation of tin oxide phase and depresses the loss of tin species from the system.

A novel synthesis of tin oxide thin films by the sol-gel process for optoelectronic applications

A novel and simple chemical method based on sol-gel processing was proposed to deposit metastable orthorhombic tin oxide (SnOx) thin films on glass substrates at room temperature. The resultant samples are labeled according to the solvents used: ethanol (SnO-EtOH), isopropanol (SnO-IPA) and methanol (SnO-MeOH). The variations in the structural, morphological and optical properties of the thin films deposited using different solvents were characterized by X-ray diffraction, atomic force microscopy, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and photoluminescence (PL) analysis. The XRD patterns confirm that all the films, irrespective of the solvents used for preparation, were polycrystalline in nature and contained a mixed phases of tin (II) oxide and tin (IV) oxide in a metastable orthorhombic crystal structure. FTIR spectra confirmed the presence of Sn=O and Sn-O in all of the samples. PL spectra showed a violet emission band centered at 380 nm (3.25 eV) for all of the solvents. The UV-vis spectra indicated a maximum absorption band shown at 332 nm and the highest average transmittance around 97% was observed for the SnO-IPA and SnO-MeOH thin film samples. The AFM results show variations in the grain size with solvent. The structural and optical properties of the SnO thin films indicate that this method of fabricating tin oxide is promising and that future work is warranted to analyze the electrical properties of the films in order to determine the viability of these films for various transparent conducting oxide applications.

RETRACTED: Comparative analysis of physico-chemical and gas sensing characteristics of two different forms of SnO2 films

Abstract In this paper the results of studies of comparative studies on the crystallinity, morphology and chemistry combined with the gas sensor response of two different forms of tin dioxide (SnO 2 ) films prepared by the Rheotaxial Growth and Thermal Oxidation (RGTO) and by the Laser-enhanced Chemical Vapour Deposition (L-CVD) methods, respectively, are presented. For this purpose the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Photoelectron spectroscopy (XPS) have been used. XRD studies for both samples show the contribution from the crystalline SnO 2 in the cassiterite rutile phase without any evident contribution from the tin oxide (SnO) phase. SEM and AFM studies show that the surface morphology of RGTO and L-CVD SnO 2 samples are characterized by grains/nanograins of different size and surface roughness. In turn XPS studies confirm that for both SnO 2 samples a slight nonstoichiometry with a relative [O]/[Sn] concentration of 1.8, and slightly different amount of C contamination at the surface of internal grains with relative [C]/[Sn] concentration of 3.5 and 3.2, respectively. This undesired C contamination cannot be ignored because it creates an uncontrolled barrier for the potential gas adsorption at the internal surface of sensor material. This is confirmed by the gas sensor response in NO 2 atmosphere of both SnO 2 samples because the sensitivity is evidently smaller for RGTO SnO 2 with respect to the L-CVD SnO 2 samples, whereas the response time showed a completely opposite tendency. It is probably caused by the smaller extension of internal surface and grain dimension with respect to the Debye length, as well as higher C contamination observed for RGTO SnO 2 with respect to L-CVD SnO 2 samples.

Luminescent properties of vanadium-doped SnO2 nanoparticles

This paper reports the influence of doping degree and annealing temperature on XRD, Raman, EPR and PL spectra of Sn1−xVxO2 nanoparticles with x=0, 0.01 and 0.05 annealed at 600 and 800°C. XRD studies reveal a tetragonal rutile crystalline phases of tin oxide, while the formation of V2O5 secondary phase was evidenced for all doped nanoparticles only by Raman scattering. In function of the doping degree and annealing temperature, from EPR spectroscopy was evidenced the presence of three different positions for V4+ ions in the samples: isolated ions disposed on the nanoparticles surface, ions which are coupled by dipolar or exchange interactions and cluster ions. The luminescence emissions associated with oxygen vacancies and structural defects are influenced by doping degree and annealing temperature and could be correlated with the crystallite size determined from XRD patterns.