Single Phase SnO2 Research Articles

Preparation of aloe-like ordered mesoporous SnO2 with excellent gas sensing property to H2S

In this study, a kind of novel and uniform 3D aloe-like morphology SnO2 material was successfully synthesized, the breadth, thickness and length of aloe-like petals were about 230 ± 10 nm, 30 ± 5 nm and 600 ± 10 nm, respectively. The ordered mesoporous were distributed on the surface of the 3D aloe-like SnO2 material whose average pore diameter was about 3.6 nm. The optimum synthesis conditions were determined, and the morphology, structure and gas sensing performance toward H2S of the prepared material were tested. The 3D aloe-like SnO2 nanomaterial showed much excellent gas sensing performance to H2S at 190 °C, whose response to 100 ppm H2S reached to 48.3 (Ra/Rg), response time was only 3 s, and detection limit was as low as 0.5 ppm. Such excellent gas sensing performance was rarely reported in past reports for the single phase SnO2 material.

Transparent conducting SnO2 thin films synthesized by nebulized spray pyrolysis technique: Impact of Sb doping on the different physical properties

The impact of antimony (Sb) doping concentration on the different physical properties of transparent conducting tin oxide (SnO2) thin films synthesized through nebulized spray pyrolysis (NSP) method have been explored systematically. X-ray diffraction (XRD) results reveal the tetragonal cassiterite structure of single phase SnO2 and the decrement of crystallite size with rising Sb doping concentration. Uniform and compact surface morphology with continuous distribution of grains and reduction of grain size with increasing dopant amount are illustrated by scanning electron microscopy (SEM). The stoichiometry of SnO2 film with 2% Sb doping is confirmed by energy dispersive X-ray spectroscopy (EDS) study. The optical transmittance is more than 85% in the visible region for undoped film and enhanced in the near infrared (NIR) spectral region for all the films. The transparency is reduced and the optical band gap is found to increase from 3.69 eV to 3.90 eV upon Sb inclusion. The extinction coefficient, refractive index, dielectric constant, dissipation factor, volume energy loss function, surface energy loss function, optical conductivity and optical density of the films are determined and interpreted for different dopant concentrations. The photoluminescence (PL) spectrum demonstrates the enhancement of emission intensity with increasing Sb incorporation representing its suitability in the application of solid state lighting. The lowest resistivity of 6.435 × 10−4 Ω cm and the highest carrier concentration of 1.316 × 1021 cm−3 are achieved for the film with 8% Sb doping concentration. The mobility of the studied degenerated films is varied from 54.743 cm2/Vs for undoped films to 7.378 cm2/Vs for 8% Sb doped film and limited by ionized impurity scattering. The film deposited with 2% Sb doping level exhibits the highest figure of merit values in both visible and NIR wavelength region indicating its better role in optoelectronic applications.

Structural, morphological and opto-electrical properties of transparent conducting SnO2 thin films: Influence of Sb doping

ABSTRACT Pure and antimony doped tin oxide (Sb:SnO2) thin solid films were synthesised through a simple and low-cost nebulised spray pyrolysis (NSP) route. The influence of Sb doping on the different physical properties of these films was systematically investigated. The results of X-ray diffraction (XRD) study exhibited polycrystalline in nature of all films with tetragonal cassiterite structure of single phase SnO2. XRD analysis also revealed the reduction in crystallite size as well as the grain size observed in scanning electron microscopy (SEM) with Sb doping concentration. The average transmittance of all the films was greater than 73% at the visible wavelength region and the transparency was reduced by Sb inclusion. The direct optical band gap value was the lowest of 3.94 eV for pure SnO2 and enhanced by Sb doping level. The effects of Sb doping concentration on extinction coefficient, refractive index, dielectric constant, optical conductivity and optical density of the films were examined. Photoluminescence spectrum revealed a broad violet emission peak near 390 nm and Sb doping intensified the peak. Both the resistivity and sheet resistance were found to vary in the range of 1.61 × 10−3 Ω.cm to 3.92 × 10−4 Ω.cm and 32.73 Ω/□ to 134.41 Ω/□, respectively with the variation of Sb doping concentration. The highest mobility and carrier concentration were 54.74 cm2/Vs and 7.02 × 1021 cm−3 for undoped and 10% Sb doped films, respectively. However, the figure of merit was found to be maximum of 1.38 × 10−3 (Ω/cm2)−1 for 5% Sb doping concentration among the films.

Properties of SnO2 and SnO2−xNx grown on the boat walls using vapor transport method

The aim of the study was to examine the properties of SnO2 and SnO2−xNx nanowires (NWs) grown on the walls of the boat of the vapor transport system. Nanowires of SnO2 and SnO2−xNx were synthesized using Ar plus O2 and N2 plus O2 gas mixtures, respectively. The obtained chemical compositions were SnO2 and SnO1.71N0.18. In both cases, tetragonal single-phase SnO2 with nanowires morphologies were obtained by X-ray diffraction and scanning electron microscopy examinations, respectively. The NWs diameters were ranged from 150 nm to 1.6 µm, and the lengths extended to more than 400 µm for the sample grown with Ar plus O2, whereas the diameters of the NWs ranged from 30 nm to 2.1 µm and the lengths exceeded to 1 mm for the sample grown with N2 plus O2. The calculated optical band gap values were 3.54 and 3.27 eV for samples grown with Ar plus O2 and N2 plus O2, respectively. Higher photoluminescence spectrum intensity was observed for SnO2−xNx NWs. The room-temperature resistivity of SnO2−xNx was one order lower than that for SnO2 NWs and decreased upon increasing temperature, indicating a semiconducting behavior. Two activation energies were recorded for each sample.

Effect of La doping on key characteristics of SnO2 thin films facilely fabricated by spin coating technique

La-doped SnO2 thin films (1, 2.5, 5.0, 7.5 and 10%) have been coated on FTO substrates by a sol-gel spin coating technique. XRD studies confirms the (100) orientation of all prepared films of polycrystalline nature. Vibrational modes confirm the fabrication of single phase SnO2 films. EDX/SEM mapping confirms the presence of La in SnO2 films. AFM reveals the grain size in range of 17–82 nm along with RMS roughness in 13 and 38 nm. The direct band gap values of pure and La doped SnO2 thin films are varying between 4.15 and 3.95 eV. The refractive index (n) and absorption index (k) values were found to be reducing below 5% La doping and showed an increasing tendency beyond 5% doping. Further, the investigated values (χ1),(χ3) and n2 were found in the range of 0.032–47, 1.5 × 10−8 to 8 × 10−4 esu and 2.3 × 10−7 to 1.2 × 10−3, respectively.

Grain refinement and non-ohmic properties in (Co, Ta)-doped SnO2 ceramics by Cr2O3 additions and the in situ formation of CoCr2O4

In this investigation, the microstructure and current–voltage properties of (Co, Ta)-doped SnO2 ceramics were found to depend on Cr2O3 additions. SnO2–Co3O4–Ta2O5 ceramics with additions of 0, 0.05, 0.1, 1 and 2 mol% Cr2O3 were sintered at 1350 °C under an oxidizing atmosphere and characterized microstructurally and electrically. Characterization by XRD and SEM shows that for samples with 0–1.0 mol% Cr2O3, the microstructure consists of single-phase SnO2 grains, while for the sample with the highest Cr2O3 content, the CoCr2O4 spinel phase is present in SnO2 microstructure. Moreover, reduced grain size distribution breadth and average grain size are observed in the SnO2 microstructure with 2 mol% Cr2O3. Results suggest that nonlinearity coefficient (α) is not as sensitive as electric field at fixed current density (EB) to Cr2O3 concentration changes.

Effect of the carrier gas on morphological, optical and electrical properties of SnO2 nanostructures prepared by vapor transport

The aim of the study was to explore the effects of carrier gas on the properties of SnO2 nanostructures grown by vapor transport method for possible optoelectronic applications. Nanostructures of SnO2 were synthesized via vapor transport method using Ar plus O2 and N2 plus O2 gas mixtures. It was found that the carrier gas (Ar or N2) has great influences on the properties of the resulting SnO2 nanostructures. Tetragonal single phase SnO2 with nanowires (NWs) morphologies was obtained for Ar/O2. The diameters of the NWs ranged from 10 to 162 nm and the lengths exceed 5 µm. While tetragonal single phase SnO2 with nanoparticles morphologies (diameters of 42–173 nm) was obtained for N2/O2. The calculated optical band gap values were 3.81 and 2.95 eV for samples prepared with Ar/O2 and N2/O2, respectively. The conduction mechanism in the samples was found to be thermally activated. Single activation energy of 0.49 eV was evaluated for the sample prepared in Ar/O2, while two activation energies (EAL = 1.48 eV and EAh = 0.83 eV) were obtained for the sample prepared with N2/O2. The photoluminescence emission (intensity and shape) depended on the carrier gas. The observed emission peaks were assigned to the oxygen vacancies and the oxygen related defects. The obtained results may find applications in optoelectronics such as light emitting diodes.

The control of abnormal grain growth in low-voltage SnO2 varistors by microseed addition

In this research, the addition effects of three different quantities of micron-sized seeds (microseeds) to a SnO2 varistor prepared from nanomaterials on the microstructure and electrical properties were studied. Moreover, surge-withstanding capability of low-voltage SnO2 varistors was investigated. The X-ray diffraction pattern disclosed a single phase SnO2 for microseed grains. The morphological features of samples were characterized using scanning electron microscopy. The abnormal distribution of grain size with elongated grains of SnO2 in fine grains matrix was observed in sintered samples without microseeds. The low content of microseed addition (0.3wt%) had not controlled abnormal grain growth, however, it increased mean grain size to 37µm. Although the high content of microseeds (7.5wt%) stopped abnormal grain growth, it had a negative effect on relative density and mean grain size. The normal grain size distribution with maximum mean grain size (45µm) was obtained in samples containing 1.5wt% microseeds. These samples showed the lowest breakdown field (240V/cm) and the highest surge-withstanding capability (1.5kA/cm2). Furthermore, the standard deviation of the electrical parameters of these samples was improved due to normal grain-size distribution.

Influence of single and binary transition metal dopants (Mn, Fe, or Co) on the structure, optical, and magnetic properties of SnO2 nanoparticles

Nanoparticles samples of pure SnO2, Sn0.99Mn0.01O2, Sn0.98Mn0.02O2, Sn0.98Mn0.01Fe0.01O2, Sn0.96Mn0.02Fe0.02O2, Sn0.98Mn0.01Co0.01O2 and Sn0.96Mn0.02Co0.02O2 were synthesized by sol-gel method. X-ray diffraction analysis and Fourier transform infrared spectra of all prepared samples confirmed the formation of single phase SnO2 with tetragonal rutile structure. The average crystallite sizes of the prepared samples were estimated to be in the range of 7–12 nm. Energy-dispersive X-ray spectroscopy analysis of Sn0.98Mn0.02O2, Sn0.96Mn0.02Fe0.02O2, and Sn0.96Mn0.02Co0.02O2 samples evidently proved the existence of Mn, Fe, Co, Sn, and O elements only without any impurity, indicating the high purity of the prepared samples. Transmission electron microscopy images showed the formation of ultra-fine spherical nanoparticles in all samples with average particles sizes of 8.5–15 nm. From the UV–Vis absorption spectra results, the band gap energy value of the pure SnO2 nanoparticles was estimated to be 3.90 eV and it varied with dopant type and its concentration. Room temperature magnetic hysteresis loops of all samples exhibited ferromagnetic behavior. Clear enhancement in the room temperature ferromagnetism was achieved in pure SnO2 nanoparticles after doping with Mn and codoping with (Mn, Fe) or (Mn, Co) dopants. The maximum value of the saturation magnetization was found in Sn0.96Mn0.02Fe0.02O sample, while Sn0.96Mn0.02Co0.02O sample displayed the higher values of coercivity and retentivity.

X-ray peak broadening and optical properties analysis of SnO2 nanosheets prepared by sol-gel method

In the present study, SnO2 nanosheets were synthesized via a sol-gel method, where gelatin was employed as the natural polymerization agent. The calcination temperature variables such as 650, 700, and 750°C were found to influence the resultant optical and structural properties. The structural properties of the SnO2 nanosheets were investigated, using Raman spectroscopy and X-ray diffraction (XRD) and were analyzed by Williamson-Hall and size strain plot methods. The Raman studies proved the formation of single-phase SnO2 structure, while there were no SnO or Sn2O3 secondary phases. The XRD results revealed that the samples were crystallized in a tetragonal structure. The morphology of the prepared samples was observed by scanning electron microscope (SEM). Furthermore, the SEM investigations demonstrated that wide-area SnO2 nanosheets were successfully obtained by using gelatin at the chosen calcination temperatures. The synthesized samples were also characterized by photoluminescence spectrometers (PL), indicating only green emission from the samples. Being a conductive semiconductor, this unique structure will have prospective applications as a conductive transparent substrate.

Carbon Encapsulated Tin Oxide Nanocomposites: An Efficient Anode for High Performance Sodium-Ion Batteries.

The major obstacle in realizing sodium (Na)-ion batteries (NIBs) is the absence of suitable negative electrodes. This is because graphite, a commercially well known anode material for lithium-ion batteries, cannot be utilized as an insertion host for Na ions due to its large ionic size. In this study, a simple and cost-effective hydrothermal method to prepare carbon coated tin oxide (SnO2) nanostructures as an efficient anode material for NIBs was reported as a function of the solvent used. A single phase SnO2 resulted for the ethanol solvent, while a blend of SnO and SnO2 resulted for the DI water and ethylene glycol solvents. The elemental mapping in the transmission electron microscopy confirmed the presence of carbon coating on the SnO2 nanoparticles. In cell tests, the anodes of carbon coated SnO2 prepared in ethanol solvent exhibited stable cycling performance and attained a capacity of about 514 mAh g(-1) on the first charge. With the help of the conductive carbon coating, the SnO2 delivers more capacity at high rates: 304 mAh g(-1) at the 1 C rate, 213 mAh g(-1) at the 2 C rate and 133 mAh g(-1) at the 5 C rate. The excellent cyclability and high rate capability are the result of the formation of a mixed conducting network and uniform carbon coating on the SnO2 nanoparticles.

Annealed SnO2 thin films: Structural, electrical and their magnetic properties

SnO2 thin films of ~150nm thicknesses were deposited on quartz substrate by pulse laser deposition technique and annealed at 600–900°C for 1h with a variation of 100°C per sample. The X-ray diffraction patterns show that as deposited SnO2 thin film was completely amorphous while annealed SnO2 thin films were randomly oriented, polycrystalline in nature and correspond to the rutile phase. The average crystallite size estimated using Scherrer and Williamson–Hall equations was found to increase with annealing temperature. In addition to the three fundamental Raman peaks at 473cm−1, 627cm−1 and 766cm−1 corresponding to the tetragonal rutile phase of SnO2, two IR active Raman bands and one Raman forbidden mode were also observed at 500cm−1, 690cm−1 and 544cm−1 respectively. The dc resistivity measurements in the temperature range of 297–400K show semiconducting behavior of all the annealed thin films. Room temperature dielectric properties of all the samples show dispersion which is explained in the light of Koop's theory based on Maxwell–Wagner two layer models. The dielectric parameters: real part of dielectric constant, dielectric loss and ac conductivity show their maximum value for SnO2 film sample annealed at 600°C. The dielectric loss shows anomalous behavior and exhibits relaxation peaks (Debye peaks) at lower and middle frequencies. Complex impedance plots (Nyquist plots) for annealed SnO2 thin films show two well-resolved semicircles corresponding to two different electrical transport mechanisms which stand for grain and grain boundary. It is observed that the contribution of grains in the conduction process starts dominating over the grain boundary with the increase in annealing temperature. From a magnetic hysteresis loop, it is clear that all the single phase SnO2 thin films annealed at different temperatures are ferromagnetic at room temperature and the value of saturation magnetization shows its maximum for the film annealed at 600°C.

SnOx/Carbon Core Shell Structure: An Efficient Anode for Rechargeable Sodium Ion Batteries

Lithium-ion batteries have been widely used as energy storage media in portable electronic devices, electrical vehicles, hybrid electrical vehicles, etc. In particular, they have become indispensable energy storage devices for intermittent energy conversion applications such as solar cells and wind power. However, the low abundance and uneven distribution of lithium resources show the potential difficulties of the long-term and large-scale applications of lithium-ion batteries in aspects of their availability and cost. Accordingly, the development of new types of batteries, such as sodium-ion and magnesium-ion batteries, is necessary. Among them, sodium (Na)-ion batteries (NIBs) possess electrochemical working principles that are similar to LIBs. In addition, sodium is inexpensive and abundant. Therefore, NIBs could substitute LIBs in applications such as smart grids and large-scale energy storage for renewable solar power and wind power. The major obstacle in realizing NIBs has been the absence of suitable anodes. Most of all, graphite which has been a commercially well-known anode material for LIBs cannot be used as an insertion host for Na ions due to their large ionic size. Moreover, only few noticeable studies on negative electrode materials, e.g., lead and hard carbon have been reported thus far. Metal oxides are considered to be important electrode materials, as they follow a conversion reaction mechanism. However, metal oxides suffer from several problems when used as anode materials which limit their use, such as swelling and shrinking of active material particles upon the insertion and extraction of Li+ or Na+ ions, which can induce poor contact between the active materials and the electron conducting agents, leading to low electric and ionic conductivity. In this study, we report the electrochemical activity of carbon coated SnOx nanostructures for NIBs. The nanostructured SnOx were synthesized by a hydrothermal method and their surfaces were coated by carbon to improve the electric conductivity. The effect of solvent used for hydrothermal process and annealing temperature on the structure, morphology and Na storage capacity was investigated. The single phase SnO2 was obtained using ethanol solvent, while the blend of SnO and SnO2 was obtained using DI water and ethylene glycol solvents. The transmission electron microscopic images conform the presence of carbon coating on the SnOx nanoparticles. Further, the anodes made of carbon coated SnOx prepared in ethanol solvent exhibited stable cycling performance and attained the capacity of about 443 mAh/g in the first charge. With the help of the conductive carbon, the carbon coated SnO2 delivered more capacity at high rates; 257 mAh/g at the 1 C-rate, 156 mAh/g at the 5 C-rate and 70 mAh/g at the 10 C-rate. The excellent cyclability and high-rate capability are attributed to the formation of a mixed conducting network and the uniform carbon coating formed on the SnO2 nanoparticles.

Magnetic and structural investigations on as-grown and oxygen annealed PLD SnO2 : Co thin films

Detailed structural and magnetic characterization has been performed on dilute magnetic oxide SnO2 : Co thin films deposited on R-cut sapphire substrates via pulsed laser deposition from a doped target of 5 at.% nominal Co concentration. These studies demonstrate that the films are highly crystalline, composed of single phase SnO2 : Co grains, with no formation of Co nanoclusters in the oxide matrix, and are ferromagnetic at room temperature. It was found that ferromagnetism and electrical conduction are strongly dependent on the growth rate, film thickness and post deposition annealing protocols and suggest that the magnetic properties are related to the number of defects, and thus the crystallinity of the films. For thicknesses above 70 nm, films are electrically conducting and ferromagnetic, with a relatively constant MS of about 20 emu cm−3 at room temperature. Moreover, the moment per unit area varies linearly with the film thickness, showing that the ferromagnetism of the studied materials is a volume property. Samples annealed in conditions similar to their growth display a dramatic increase of MS in the first 5 min of annealing. Temperature dependent magnetization measurements reveal that approximately one third of the cobalt couples ferromagnetically with the remaining two thirds existing in the form of paramagnetic isolated cobalt spins. Experimental evidence supports the conclusion that films are formed of single crystal grains of SnO2 doped with Co, held together by defect-rich grain boundaries.

Microwave-assisted synthesis of SnO2 nanorods for oxygen gas sensing at room temperature

High-quality single-crystalline SnO2 nanorods were synthesized using a microwave-assisted solution method. The nanorods were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), ultraviolet-visible and Raman spectroscopy, Brunauer–Emmett–Teller (BET), and electrical resistance measurements. The XRD pattern indicated the formation of single-phase SnO2 nanorods with rutile structure. FE-SEM and TEM images revealed tetragonal nanorods of about 450–500 nm in length and 60–80 nm in diameter. The nanorods showed a higher BET surface area of 288 m2/g, much higher than that of previously reported work. The Raman scattering spectra indicated a typical rutile phase of the SnO2. The absorption spectrum showed an absorption peak centered at 340 nm, and the band-gap value was found to be 3.64 eV. The gas-sensing properties of the SnO2 nanorods for oxygen gas with different concentrations were measured at room temperature. It was found that the value of resistance increased with the increase in oxygen gas concentration in the test chamber. The SnO2 nanorods exhibited high sensitivity and rapid response-recovery characteristics to oxygen gas, and could detect oxygen concentration as low as 1, 3, 5, and 10 ppm.

Facile Synthesis of Characteristic Tin Oxide Particulate Films in Aqueous Solution

Characteristic tin oxide films were formed on transparent conductive substrates in aqueous solutions. Surface of the films consisted of ellipse‐shaped particles. Particle size in longer or shorter direction was about 300–400 or 200 nm, respectively. In contrast, middle and bottom area of the films were dense structures. Thickness was about 1150 nm. The film was single phase SnO2 with a‐axis orientation. The films had chemical ratio of O/Sn = 1.20–1.37 and F/Sn = 0.088–0.124, suggesting fluorine doping. Facile synthesis of tin oxide particulate films had advantages in ordinary temperature synthesis, water solvent process, and low‐environmental load.

Characterization of SnO<sub>2 </sub>Nanoparticles Prepared by Two Different Wet Chemistry Methods

Effects of synthesis techniques, namely sol gel method and direct growth method on the nanostructural and optical properties of SnO2 have been investigated. The XRD results confirmed that both samples are single phase SnO2. The crystallite size of SnO2 prepared by sol-gel and direct growth method were approximately 10 nm and 15 nm respectively. The FE-SEM micrographs displayed that SnO2 nanoparticles prepared by sol gel method exhibited a round shape with approximate particle size of 10 nm while the direct growth method produced SnO2 nanorod with length and width of 570 nm and 55 nm respectively. The direct Eg for both SnO2 nanospheres and nanorods are 3.98 eV and 3.94 eV respectively, Due to quantum confinement effect, both nanomaterials exhibited strong blue shift compared to bulk material with Eg of 3.6 eV.

A stable, low turn-on field of SnO2 : Sb–SiO2 core–shell nanocable emitters

Nanocables have been formed with Sb-doped SnO2 (SnO2 : Sb) cores and SiO2 shells. First, SnO2 : Sb nanowires were synthesized by a vapour–liquid–solid process at 900 °C. Subsequently, thin SiO2 shells were deposited onto the surfaces of these SnO2 : Sb nanowires. Thin-film x-ray diffraction showed that all the as-synthesized core–shell nanocables had a single-phase SnO2 rutile structure. Field emission scanning electron microscopy revealed that the nanocables had diameters of 80–140 nm and lengths of up to several hundred micrometres. As-synthesized SnO2 : Sb–SiO2 core–shell nanocables revealed an extremely low turn-on field, ∼0.35 V µm−1, which was seven times lower than the ∼2.3 V µm−1 field of SnO2 : Sb nanowires.

The Crystal Structure and Gas Sensing Property of Tin Oxide Films Sputtered in N<sub>2</sub>/O<sub>2</sub> Atmosphere

The usage of mixed N2/O2 gas in the preparation of tin oxide thin films by sputtering was examined in order to clarify the relationship between the resulting crystal structure and the H2 gas sensing properties. The formation of single-phase SnO2 and the degree of preferential orientation of the (110) plane were improved by increasing the oxygen concentration in the sputtering gas. A higher gas sensitivity was observed in films having higher degrees of the orientation of the (110) plane, and the maximum sensitivity was increased by about 1.5 times of that for the film prepared in Ar/O2 atmosphere.

Deposition of tin oxide films by pulsed laser evaporation

Thin films of SnO2−x (0<x<1) were deposited on Corning glass and alumina substrates by employing a pulsed laser evaporation (PLE) technique. The microstructural features of the films were probed with Sn119 conversion electron Mössbaucr spectroscopy (CEMS) whereas the structural characteristics were identified by using low-angle x-ray diffraction measurements. The electrical and optical properties have also been studied. It is shown that films with conductivity of 3 × 102 (ohm·cm)−1 and transmission of 90% can be obtained by appropriate postannealing of the as-deposited films in air and vacuum. The energy gap of this nearly stoichiometric single-phase SnO2 film was found to be 3.5 eV and spectroscopic ellipsometry measurements indicated the refractive index lobe typically between 1.8–1.9 over the wavelength range of 400–800 nm.