SnO2 Samples Research Articles

Stable high dielectric properties in (Cr, Nb) co-doped SnO2 ceramics

In this research, the microstructure, dielectric, and non-Ohmic properties of (Cr, Nb) co-doped SnO2 ceramics, (Cr0.5, Nb0.5)xSn1-xO2 with x% = 0, 0.5, 1.0, 2.0, 5.0, and 10.0, as a colossal dielectric material and a prospective alternative to co-doped TiO2 ceramics were studied. The X-ray diffraction results indicated that in all compositions, the cassiterite phase was achieved without any secondary phases. Moreover, field-emission secondary electron microscopy showed that the microstructure of samples has different morphologies including typical grains, enlarged grains and prism-like grains microstructure for various sintered samples. The maximum dielectric constant (2737) accompanied by the lowest dielectric loss (0.04) at the frequency of 1 kHz was obtained for (Cr0.5, Nb0.5)0.02Sn0.98O2. The all co-doped SnO2 samples except for x = 10.0 showed non-Ohmic properties. Based on the observed non-Ohmic properties, the mechanism of dielectric properties of (Cr, Nb)-doped SnO2 ceramics was attributed to the internal barrier layer capacitor (IBLC) model. According to this model, samples with higher breakdown electric field demonstrate the better stability of dielectric properties, when DC bias voltage is applied.

Visible light active heterostructured photocatalyst system based on CuO plate‐like particles and SnO2 nanofibers

AbstractIn this study, CuO–SnO2 p‐n type heterostructures were produced and tested for the degradation of methylene blue and 4‐nitrophenol under visible light irradiation. CuO particles were produced in plate‐like morphology using hydrothermal synthesis. SnO2 nanofibers were obtained by electrospinning. Structural, morphological, optical and semiconducting property characterization of heterostructured CuO–SnO2 and individual phases were performed. The photocatalytic activity was found to change depending on the amount of CuO particles in heterostructured samples. Among others, the sample with 0.35 wt.% CuO–SnO2 showed the highest photocatalytic efficiency with a degradation rate constant ~2 h−1. Active specie scavenger tests revealed that the decomposition reaction occurs through direct oxidation mechanism by the holes in the valence band of SnO2 in pure samples whereas in CuO–SnO2 samples and radicals also form and involve in the reactions. Further, the photocatalytic degradation mechanism was revealed using relative band potentials and p‐n junctions of the heterostructured photocatalyst.

Porous SnO2 nanostructure with a high specific surface area for improved electrochemical performance.

Tin oxide (SnO2) has been attractive as an alternative to carbon-based anode materials because of its fairly high theoretical capacity during cycling. However, SnO2 has critical drawbacks, such as poor cycle stability caused by a large volumetric variation during the alloying/de-alloying reaction and low capacity at a high current density due to its low electrical conductivity. In this study, we synthesized a porous SnO2 nanostructure (n-SnO2) that has a high specific surface area as an anode active material using the Adams fusion method. From the Brunauer–Emmett–Teller analysis and transmission electron microscopy, the as-prepared SnO2 sample was found to have a mesoporous structure with a fairly high surface area of 122 m2 g−1 consisting of highly-crystalline nanoparticles with an average particle size of 5.5 nm. Compared to a commercial SnO2, n-SnO2 showed significantly improved electrochemical performance because of its increased specific surface area and short Li+ ion pathway. Furthermore, during 50 cycles at a high current density of 800 mA g−1, n-SnO2 exhibited a high initial capacity of 1024 mA h g−1 and enhanced retention of 53.6% compared to c-SnO2 (496 mA h g−1 and 23.5%).

A Simple Dip-Coating Method of SnO2-NiO Composite Thin Film on a Ceramic Tube Substrate for Methanol Sensing

In this work, SnO2-NiO composite thin film was successfully grown on a ceramic tube substrate directly by a simple dip-coating method combined with annealing. Characterization analysis demonstrates that uniform SnO2 film consists of a great number of nanospheres and NiO grows on SnO2 as an agglomerated block. In comparison to the pure SnO2 sample, the SnO2-NiO composite thin films gas sensor exhibits superior methanol sensing properties at 225 °C. The gas response to 10 ppm methanol reached 15.12 and the response and recovery times were 8 s and 7 s, respectively. The excellent selectivity and recovery rate are explained by the unique properties of the NiO semiconductor and the higher sensor response is attributed to the pivotal heterojunction effect.

Influence of Cd substitution and temperature on dielectric properties of SnO2

The temperature dependence of dielectric properties of Cd-doped SnO2 nanoparticles has been carried out successfully in the temperature range 30 to 300 °C at specific frequencies. The dielectric constant of pure and Cd-doped SnO2 sample at selected frequency increases with increasing temperature. The loss tangent of pure and doped materials has also been examined. Ac conductivity of Cd incorporated SnO2 samples increases with increasing temperature. Further, the activation energies at different frequencies for all samples have been estimated.

Pr doped SnO2 nanostructures: Morphology evolution, efficient photocatalysts and fluorescent sensors for the detection of Cd2+ ions in water

We report the effect of Pr doping on structural, morphological, optical, photocatalytic properties and heavy-metal ion sensing behavior of 3D flower-like SnO2 nanostructures synthesized using hydrothermal method by varying Pr concentration from 0 to 10 mol%. The synthesized samples have been characterized by various analytical techniques. The results indicate that the morphology of SnO2 nanostructures can be tailored by changing the Pr-dopant concentration in a reasonable range. Crystallographic studies reveal the lattice distortion with an increase in Pr doping concentration in SnO2 host lattice. Moreover, the photocatalytic activity of SnO2 studied by the degradation of Rhodamine-B (RhB) dye in aqueous media shows excellent performance on 10 mol% praseodymium doping, which may be attributed to its specific morphology, smaller size and larger surface area as seen from BET measurements. Further, the sensors based on 10 mol% Pr-doped SnO2 nanostructures shows highest fluorescence quenching efficiency (0.22) as compared to pure SnO2 and other doped samples at lowest concentration of Cd2+ (0.01 μg/ml) in drinking water with Limit of Detection (LOD) as low as 0.008 μg/ml. The possible formation mechanism of Pr-doped SnO2 nanostructures and the heavy metal-ion sensing mechanism of sensors has been proposed and discussed in detail.

Identifying Surface Active Sites of SnO2: Roles of Surface O2–, O22– Anions and Acidic Species Played for Toluene Deep Oxidation

To elucidate the nature and states of the surface oxygen sites on SnO2 and the relationship between the surface vacancies and the active oxygen sites, a series of SnO2 samples have been fabricated ...

High-pressure structural change in the ferroelectric layered perovskite Sr2Nb2O7

The structural changes of sintered powder samples of perovskite-slab layered polycrystalline ${\mathrm{Sr}}_{2}{\mathrm{Nb}}_{2}{\mathrm{O}}_{7}$ (SNO) ferroelectric compound subjected to high pressures are here investigated. The samples were prepared using a solid-state reaction in the presence (SNOE) or absence (SNO) of an applied electric field. Density functional theory (DFT) calculations including hydrostatic pressure indicate that SNO's ferroelectricity remains up to 25 GPa in the structure of space group $Cmc{2}_{1}$ derived from the condensation of one zone-center soft phonon. The predicted DFT theoretical structural changes are discussed and compared with the results of the experimental Raman spectra as a function of pressure. The pressure-dependent spectra were recorded from atmospheric pressure up to 11.5 and 13.5 GPa for SNOE and SNO, respectively. Both samples underwent a pressure induced phase transition from an incommensurate to a commensurate state at room temperature, SNO at ${P}_{i\ensuremath{-}c}=6.5\ifmmode\pm\else\textpm\fi{}0.2$ GPa, and SNOE at ${P}_{i\ensuremath{-}c}=6.9\ifmmode\pm\else\textpm\fi{}0.3$ GPa. The DFT calculations enable the identification of the change in phase to the orthorhombic structure with the space group $Cmc{2}_{1}$. The experimental values for ${P}_{i\ensuremath{-}c}$ are in reasonably good agreement with the theoretical predicted value of \ensuremath{\sim}7.3 GPa. After the critical pressures, the number of observable phonons decreases, that is, when the compound adopts a higher symmetry structure, several phonons vanish abruptly in both the SNO and SNOE samples, as expected. The Raman spectra for both samples show hysteresis effects, that is, after the pressure is removed, a few extra lines remain visible, as well as many relative intensity changes and broadenings for some phonon bands. The bulk moduli of the $\mathrm{S}{\mathrm{r}}_{2}\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{7}$ before and after ${P}_{i\ensuremath{-}c}$ are calculated resulting in 117.0 and 147.8 GPa, respectively. The Gr\uneisen parameters of the phonons observed are finally calculated and discussed.

Inclusion of cobalt reinforced Ag doped SnO2 properties: electrical, dielectric constant, magnetic and photocatalytic insights

Cobalt as a second dopant played remarkable roles in enhancing the electrical conductivity, dielectric constant, ferromagnetic and photocatalytic properties of Ag doped SnO2 nanoparticles. Pure, Ag doped and Ag/Co codoped SnO2 nanoparticles were synthesized by co-precipitation method. Rietveld refinement analysis for XRD data confirmed the single phase nature in all SnO2 compositions with tetragonal rutile structure. The noticeable changes in the unit cell volume of SnO2 established for the successful incorporation of Ag and Co ions into its host lattice. SEM and TEM images clearly showed the formation of very fine spherical nanoparticles with uniform distribution. The binary dopants of Ag/Co ions induced blue shifts in SnO2 band gap due to Burstein-Moss effect. Notable increases in the electrical conductivity of (Ag, Co) codoped SnO2 samples compared to pure one were detected. The adsorption and desorption of the oxygen species on SnO2 surface have showed significant influences on the conductivity-temperature behavior. The dielectric constant as function of frequency was discussed based on the Maxwell–Wagner model. Sn0.97Ag0.01Co0.02O2 structure exhibited the highest dielectric constant of 3129 at low frequency (42 Hz). Also, insertion of Co plus Ag ions stimulated perfect ferromagnetic loops and enriched the magnetic parameters of SnO2. The enhanced ferromagnetism was discussed based on F-center exchange interaction between Co2+ ions via oxygen vacancies (↑Co2+–↓Vo–↑Co2+). Besides that, the load of Co ions made a high jump in the photocatalytic activity of Ag doped SnO2. High activity, 97%, for methylene blue (MB) degradation was realized through Sn0.95Ag0.01Co0.04O2 catalyst with practical efficiency stability for three cycles within 97–88%. Cobalt played a main role in the separation of the photogenerated electron–hole pairs plus oxygen vacancies formation which improved the photocatalytic activity.

ZnO-modified SnO flower-like microstructures with enhanced photocatalytic performance

AbstractA flower-like SnO/ZnO heterojunction photocatalyst with high catalytic activity was synthesized by a simple ultrasonic reaction method. Results show that the SnO/ZnO composites consist of SnO, SnO2, and ZnO. The flower-like structure is made of many SnO nanosheets with a thickness of approximately 20 nm and length of 1–2 μm. A tight interface combination of SnO, SnO2, and ZnO clearly improves the photoactivity of SnO. The photocatalytic performance of the SnO/ZnO composite is much higher than that of ZnO raw materials and SnO sample. The degradation rate of the methyl orange of the SnO/ZnO composite is 99% within 60 min under visible-light irradiation.

Facile Synthesis of Nano-Diced SnO2–ZnO Composite by Chemical Route for Gas Sensor Application

The simple chemical bath deposition (CBD) method is used to synthesize SnO2–ZnO nanocomposite at room temperature. Formation of SnO2–ZnO nancomposite is confirmed by the x-ray diffraction (XRD) pattern of annealed films. Scanning electron microscopy (SEM) micrographs of nanocomposite SnO2–ZnO depict that morphological change from nanocubes to manifold hexagonal nanorods with an increase in ZnO content in a composite sample. Also, pure SnO2 sample exhibits interconnected nanospheres. Electron dispersive spectroscopy (EDS) is employed to confirm elemental compositions in composite films. SnO2–ZnO samples were applied as a sensor for different test gases, namely liquified petroleum gas (LPG), ethanol, ammonia (NH3), and hydrogen sulfide (H2S). The maximum response of 59.67% is observed for ethanol at an operating temperature of 275°C and 24 ppm gas concentration. Also, a composite sensor shows a quick response in comparison with a bare sensor. This superior performance of composite over pure sensor may be attributed to a n–n heterojunction at intergrain boundaries. The SnO2–ZnO sensor is found to be selective towards ethanol even at lower gas concentrations.

Preparation of rare-earth thulium doped tin-oxide thin films and their applications in thin film transistors

Tm3+ doped SnO2 semiconductor thin films were prepared by RF magnetron sputtering method. The doping effects of rare-earth thulium on the crystal structures, optical properties, chemical compositions, surface morphologies of tin-oxide thin films, together with the electrical properties of the corresponding SnTmO thin film transistors (TFTs), were investigated. SnTmO semiconductor thin films with polycrystalline structures feature a wide bandgap of over 3.8 eV. XPS results reveal the typical photoelectron signals of Sn4+ and Tm3+. Smaller crystallite size and more grain boundaries can be formed in doped SnO2 samples which may be responsible for the degradation of device mobility. It was found that the electrical properties of SnO2 TFTs can be modulated by Tm3+ incorporation. The appropriate Tm3+ doping concentration is around 1.6 at.% within our experimental conditions. The optimized field-effect mobility, subthreshold swing, threshold voltage, on-off current ratio and the interface trap density are 5.5 cm2 V−1 s−1, 0.618 Vdec−1, −2.3 V, 5 × 107 and 6.7 × 1011 cm−2, respectively. Stability measurements show threshold voltage shifts of 12.3 V and −11.7 V in PBS and NBS process respectively. This study may provide useful understandings on rare-earth doped SnO2 semiconductors.

Effect of the dopant on the structural and hyperfine parameters of Sn0.95M0.05O2 nanoparticles (M: V, Mn, Fe, Co)

In this work, we present a comparative study of the structural and hyperfine parameters on tin dioxide nanoparticles doped with different transition metal elements. The nanopowders with the stoichiometry Sn0.95M0.05O2 (M: V, Mn, Fe, Co) were synthesized by simple co-precipitation method. The characterization was carried out by conventional x-ray diffraction technique, transmission 119Sn Mössbauer spectroscopy and x-ray photoelectron spectroscopy (XPS). The effect of dopant element on structural parameters of tin dioxide and, particularly, on hyperfine parameters of Sn was analysed. It was found that dopants, except for Fe, were in two valence states. For the Mn-doped SnO2 sample, it was found the strongest influence of M cation on Sn hyperfine parameters, whereas Co-doped sample resulted in the least altered one as compared to doped and un-doped SnO2. We propose an explanation of the changes of the hyperfine parameters observed over the modification of the structural changes, based on the size of the dopant elements, whose oxidation states were identified by XPS. Additionally, it should not be discarded the relevant role of oxygen vacancies whose presence on the surface was indirectly witnessed by XPS.

Effect of doping and annealing on the electronic structure and magnetic properties of nanoscale Co and Zn co-doped SnO2: An experimental study and first-principles modeling

The influence of Co and Zn co-doping and annealing on the structure and magnetic properties of SnO2 nanoparticles were investigated in relation to electronic structure. The powder X-ray diffraction patterns revealed single phase tetragonal rutile structure for both as-synthesized and annealed Co and Zn co-doped SnO2 samples. The results of XPS and first-principles modeling emphasized that both the co-doped metals incorporated to SnO2 host lattice with an oxidation state of 2 + inducing the formation of oxygen vacancies under cation substitution of tetravalent Sn. Moreover, XPS spectra showed the O/(Sn + Co + Zn) ratio which has been strongly reduced under annealing for creating additional oxygen vacancies. Field dependent magnetization studies demonstrated the existence of room temperature ferromagnetism (RTFM) for the as-synthesized co-doped (Co, Zn: SnO2) and all the annealed samples. The origin of observed RTFM was correlated to the oxygen vacancies. The results of first-principles modeling demonstrated that the increase in the concentration of Co/Zn dopant offers not just an increase of total magnetic moment of the system but also control the magnetic interactions between magnetic moments on metal ions and oxygen atoms. The combination of experimental and theoretical techniques unveiled a correlation between observed RTFM and dopant atom interactions within a host lattice. Our findings provide new insight into the interaction of transition metals (Co/Zn) within co-doped systems and new evidence for the oxygen vacancy-mediated room temperature ferromagnetism.

Zn doping effect on the properties of SnO2 nanostructure by co-precipitation technique

Nanocrystalline tin dioxide (SnO2) doped with Zn (1, 2, 3, and 4% molar ratio) was synthesized via co-precipitation method. The influences of replacing tetravalent Sn4+ ions of SnO2 by divalent Zn2+ ions on their structural, optical and morphological properties were studied. The XRD pattern showed the rutile tetragonal phase for all doped and undoped SnO2 samples. The XRD studies further confirmed that the average crystallite sizes of the doped samples decreased with the increasing of dopant concentrations. The SEM images verified that the grain size and surface morphology changed with the concentration of Zn2+ doping. The EDX analyses confirmed that the prepared nanomaterials were composed of the expected elements tin, oxygen and zinc. The optical properties of the nanomaterials were investigated by means of UV–Vis spectroscopy technique. The band gap energies were calculated using Tauc’s method and it was found to decrease when Zn2+ concentration increased. Room temperature photoluminescence study at the excitation wavelength of 280 nm showed strong and weak emission peaks between 340 and 420 nm.

Structural, optical, magnetic and dielectric studies of SnO2 nano particles in real time applications

Pure and Aluminium doped (x = 0.01, 0.02, 0.03, 0.04) SnO2 nano particles have been prepared by Sol Gel method. XRD studies confirm tetragonal structure of SnO2 and second phase peaks are absent. The obtained crystallite size of undoped SnO2 is 17.5 nm and with Al insertion Crystallite size reduced to 10 nm for Sn0.96Al0.04O2. FTIR data in the range of 550 cm−1–630 cm−1 confirms the vibration modes of SnOSn and SnO in SnO2 molecules. UV spectrum shows red shift due to the trapping of exitons by oxygen vacancies. In contrast to quantum confinement energy gap decreases from 3.7 eV for undoped SnO2 and to 2.91 eV for Sn0.97Al0.03O2 due to the band bending, which is the result of particle size reduction and then increases to 3.19 eV. This variation has been explained based on Burstein-Moss effect for Sn0.96Al0.04O2. Impedance studies of undoped and Al doped SnO2 samples have been investigated at room temperature and found that Sn0.97Al0.03O2 exhibits peculiar behaviour of having high dielectric constant, high A.C. conductivity, low dielectric loss and high theoretically calculated mobility among Al doped SnO2 samples. The data obtained from Vibration Sample Magnetometer shows typical conversion of magnetic nature of undoped SnO2 which is diamagnetic to paramagnetic in the case of Sn0.99Al0.01O2 and Sn0.98Al0.02O2 samples and to superparamagnetic nature for Sn0.97Al0.03O2 and Sn0.96Al0.04O2.

Synthesis, Characterization and Gas Sensing Properties of Ga-Doped SnO2 Nanostructures

In this work influence of Ga-doping on the sensor response and selectivity of SnO2 based sensors has been investigated in detail. The effect of in-plane and bridging oxygen vacancies on the gas sensing properties of SnO2 has also been investigated. Raman and photoluminescence results revealed that defect concentration increases with increase in Ga concentration. A Brunauer–Emmett–Teller (BET) study disclosed that specific surface area increases with increase in Ga content. It has been observed that Ga-doped SnO2 nanostructures exhibited temperature dependent selectivity towards acetone and hydrogen. It is found that a 3% Ga-doped SnO2 based sensor is selective to acetone at 200°C while it is selective to hydrogen at 300°C. The observed temperature dependent selectivity of 3% Ga-doped SnO2 might be due to its different catalytic properties towards acetone and hydrogen. The increased surface area and abundant in-plane oxygen vacancies of Ga-doped SnO2 samples provided an enhanced sensor response towards 100 ppm of acetone and hydrogen, respectively. The influence of particle size on the intergranular activation energy has been investigated as well.

Effect of process parameters on the visible light photocatalytic performance of SnO by microwave synthesis

The effects of synthesis parameters, including pH, solvent, and output energy mode, on the synthesis and photocatalytic activity of SnO were investigated. The results exhibited that Cl-doped SnO samples with a particle size of approximately 50 nm were successfully obtained, with a BET surface area of approximately 7 m2/g. These parameters showed weak effects on phase composition, morphology, and particle size; however, they affected the degradation efficiency of SnO samples to MO. The optimum degradation efficiency of SnO samples to MO can be obtained by using an appropriate proportion of water and alcohol, acid condition, and three modes of output.

Oxygen vacancy modulation of commercial SnO2 by an organometallic chemistry-assisted strategy for boosting acetone sensing performances

Oxygen vacancies play a critical role in the sensing performances for metal oxides-based chemiresistor-type sensors. Developing facile and effective strategies for fabricating metal oxides with controllable oxygen vacancies is in great demand but remains paramount challenge. Herein, a novel organometallic chemistry-assisted method is reported to prepare SnO2 samples containing controllable surface oxygen vacancies. This new approach combines modification of SnO2 with dimethyltin dichloride, and subsequently thermal treatment in air atmosphere. Taking commercial SnO2 as an example, it is found that the optimized SnO2 sample possesses highest surface oxygen vacancy concentration of 37.13%. Owing to increased oxygen vacancy concentration, the resulting SnO2 sample (SnO2-Sn-0.5) presents excellent sensing performances for detection of acetone, including high response, fast response and recovery rate, good selectivity, compared with pristine SnO2 with low oxygen vacancy concentration (28.66%). This work paves a new avenue for fabricating metal oxides with controllable oxygen vacancies for various applications of sensing, energy storage, and so on.

Preparation of Cl doped SnO powder with excellent photocatalytic property by mechanical alloying

Cl-doped SnO photocatalysts were synthesized by mechanical alloying (MA) from SnCl2 and NH4HCO3. The effects of MA time on the structural characterization and photocatalytic activity of SnO powders were studied. Cl-doped SnO nanoparticles can be obtained by MA treatment after 1 h, but MA time considerably affected the crystalline size, microstrain, and photocatalytic properties of the samples. The crystalline size and specific surface area of the SnO samples gradually decreased and their microstrain increased with prolonged MA time. The peak intensity of the photoluminescence spectra of the Cl-doped SnO samples remarkably increased with prolonged MA time. Moreover, the MA samples had good photocatalytic properties. The photodegradation rate of methyl orange dye in 30 min over Cl-doped SnO nanoparticles obtained by MA for 2, 4, and 8 h was approximately 99%. Aging treatment of the SnO samples remarkably affected their phase composition, which can enhance the transformation of SnO to SnO2. The SnO2 transformation degree significantly increased with prolonged MA time through aging treatment, which also slightly deteriorated the degradation efficiency of the samples.