Sb-doped Samples Research Articles

Investigation on Sb-doped SnO2 as an efficient sensor for the detection of formaldehyde

The applicability of antimony-doped tin dioxide (Sb-doped SnO2) as a very precise sensor for detecting formaldehyde (HCHO) gas is investigated in this study. The sol-gel method was used to prepare pure SnO2 and Sb-doped SnO2 nanostructures, which resulted in better structural and morphological properties. The prepared samples were analyzed using several characterization techniques, including X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). A structural investigation indicated the presence of a tetragonal SnO2 phase with a clear preference for the (110) orientation. Furthermore, the crystallite size reduced as the quantity of Sb doping rose. According to FE-SEM analysis, both the undoped (SnO2) and Sb-doped SnO2 samples had polyhedral structures. FTIR analysis verified the presence of organic functional groups in the prepared powder samples. The optical band gap (Eg) values decreased with an increasing concentration of Sb doping in the SnO2 nanostructures. XPS was used to determine the chemical elements of the prepared powder samples. In the gas sensing study, those based on 8 wt% Sb-doped SnO2 (referred to as ATO-8) outperformed the others. At room temperature, the ATO-8 sample demonstrated stronger sensor response, faster response and recovery durations (98 s/74 s), and linear behavior. These enhancements can be attributable to an increase in adsorbed oxygen species caused by Sb doping, highlighting ATO-8's potential as a substance for detecting HCHO. This study emphasizes the potential of ATO-8 as a significant resource for practical use in the detection of HCHO, with benefits such as improved indoor air quality, increased industrial safety, and advancements in environmental monitoring.

Effects of Ta, Nb, Ba, and Sb concentration on structural, electrical, and optical properties of SnO2 thin films prepared by metal organic decomposition using spin coating

Ta-, Nb-, Ba-, and Sb-doped SnO2 thin films were prepared by the metal organic decomposition (MOD) method using spin coating. The effects of dopant concentration on the structural, electrical, and optical properties were investigated. The growth of polycrystalline films with the tetragonal rutile structure was confirmed by X-ray diffraction and atomic force microscopy measurements. The resistivity of Ta-, Nb- and Sb-doped SnO2 samples decreased to ∼10−3 Ωcm for dopant concentrations of around 1.5–3.0 at.%. The lowest resistivities were obtained for Ta- and Sb-doped SnO2 samples. On the other hand, no decrease in resistivity was observed for Ba-doped SnO2 samples. The band gap energy of Ta-, Nb-, Ba-, and Sb-doped SnO2 samples appeared to be larger than for those prepared by other methods. It was suggested that the structural deterioration may be related to the increase in the band gap energy for MOD prepared samples in addition to the Burstein-Moss effect.

Room temperature ferromagnetism in Sb doped ZnO

Using first-principle calculations, the magnetic properties of the monovacancies and the Sb-related defects including VZn, VO, SbZn, SbO, SbZn-VZn and SbZn-2VZn are studied. It is found that the isolated VZn with the charge state of 0 and −1 can contribute to ferromagnetism in ZnO material. The substitution of Sb on O sites (SbO0) also results in magnetic property. Moreover, the SbZn-2VZn complex is another defect having non-zero magnetic moment and energetically favors for the ferromagnetic state. The resultant density of states (DOS) and spin density distribution clearly show that the ferromagnetic interaction is majorly due to the O-p Zn-d and Sb-p states. To check this calculation, Sb-doped ZnO samples were grown by pulsed laser deposition with different Sb composition under P(O2) = 1.3 Pa. SQUID study showed that all of these samples are ferromagnetic at room temperature. The variation of the saturation magnetization against the Sb composition is discussed.

Enhanced electric field induced strain in B-site Sb doped BiFeO3-BaTiO3 lead free ceramics

Antimony modified 0.67BiFeO3-0.33BaTiO3 based ceramics with pure perovskite structure have been fabricated by conventional solid-state reaction method. The effects of single Sb ion doping on the microstructure, permittivity, electric field induced strain (S) and ferroelectric performance are investigated systematically. The XRD and permittivity analysis results indicate a mixed phase of pseudo-cubic and rhombohedral at morphotropic phase boundary (MPB). Compared with other single ion doped BF-BT systems, Sb doped samples show a large strain under relatively small electric field. The highest unipolar strain (0.168%) and converse piezoelectric coefficient d33* (336 pm/V) at 50 kV/cm are obtained in 0.67BiFe99.75%Sb0.25%O3-0.33BaTiO3 ceramic, Which may be attributed to the domains wall movement facilitated by the soft effect of donor doping Sb. This work suggests simple single B-site ion doping can also effectively improve the electromechanical performance of BiFeO3-BaTiO3 based ceramics under low electric field.

Promoting effect of Sb on the selective catalytic reduction of NO with NH3 over CeVO4 catalyst

A series of Sb-doped CeVO4 samples were synthetized by hydrothermal method and used in selective catalytic reduction of NO with NH3. Contrasted with other catalysts, Sb2CeVO4 possessed superior NH3-SCR activity and excellent SO2 tolerance. Besides, the characterization results testified that Sb species in Sb2CeVO4 could reduce the crystallization of CeVO4, and improve the surface acidity and reducibility. Moreover, the existence of Sb3+ was beneficial to generate more surface adsorbed oxygen species. Based on the in situ DRIFT spectra, more ad-NH3 and ad-NOx species with higher reactivity were obtainable on Sb2CeVO4 catalyst compared with that on CeVO4 catalyst, which also contributed to enhancing the SCR activity by Langmuir-Hinshelwood (L-H) mechanism effectively.

Vacancy engineering in rock-salt type (IV-VI)x(V-VI) materials for high thermoelectric performance

This study proposes a rational approach for controlling vacancy and carrier concentrations simultaneously by introducing V-VI chalcogenide into rock-salt structured IV-VI, where V, IV, and vacancy occupy the cationic sites, and VI occupies the anionic sites. For proof-of-concept experiments, Sb2Te3 is introduced in SnTe matrix, leading to the formation of vacancies (□SnxSb2Tex+3, where □ is vacancy) and dense dislocations in grains, along with an optimization of p-type carrier concentrations. Unlike simple Sb-doped Sn1-xSbxTe samples, the □SnxSb2Tex+3 samples in this study show a much lower lattice thermal conductivity and an enhanced power factor at a similar carrier concentration level. Specifically, the lattice thermal conductivity of □Sn10Sb2Te13 sample approaches the theoretical value of SnTe (amorphous limit) due to the strong phonon scattering caused by the large difference in mass and local strain near the dense dislocations formed from the clustering of vacancies and partly from the scattering from Sb. Such simple approach leads to boosting the thermoelectric performance of SnTe without any complex manipulations by using high-cost, harmful dopants.

The origin of additional modes in Raman spectra of ZnO:Sb films

Systematic Raman spectroscopic study was conducted on the wurtzite (002) Sb-doped ZnO films grown by pulsed laser deposition with different Sb doping levels and annealed at different temperatures, with the undoped, Cu-doped and Ga-doped ZnO films for comparison. Three additional Raman modes 235 cm−1, 510 cm−1 and 534 cm−1 were observed only in the Sb-doped ZnO samples but not in the other controls. The vibration mode 235 cm−1was associated with the SbZn-related shallow donor, which was the origin of the n+-conductivity. The 510 cm−1 vibrational mode has been associated with HO in previous literature. However in the current study, the correlation between its intensity and the H abundance was not observed. The 534 cm−1 Raman mode was associated with a Sb-related defect. The variation of the intensities of the Raman modes 235 cm−1 and 510 cm−1 upon annealing and change of Sb composition were discussed.

Annealing of the Sb-vacancy and a closely related radiation induced defect in n-type germanium

Deep level transient spectroscopy was used to study the defects induced by alpha-particle irradiation from an Am241 source in antimony doped n-type germanium. Previous investigations of the well know Sb-vacancy defect have led to the discovery of a second defect with very similar emission properties, referred to as the E′. Although both defects have similar emission rates, they have very different annealing properties. In this study we further investigated these properties of the E′ in Sb doped samples irradiated at 270K with alpha particles from an Am241 source. Laplace deep level transient spectroscopy was used to determine the concentration of each defect. An isothermal annealing study of the E′ was carried out in the temperature range 300K to 325K in 5K increments, while the Sb-vacancy was annealed out completely at 410K onwards, long after the E′ was completely annealed out. The annealing activation energy was determined through isothermal annealing profiles for both the Sb-Vacancy and the E′ as 1.05eV and 0.73eV respectively with a prefactor of 2.05 × 109s−1 and 2.7 × 108s−1.

Thermoelectric properties of dense Sb-doped SnO2 ceramics

In the present study thermoelectric properties of spark plasma sintered and subsequently air-annealed Sn1-xSbxO2 (x = 0, 0.01, 0.03, 0.05) ceramic samples were characterized. It was observed that addition of Sb greatly affects density, microstructure and thermoelectric properties of SnO2. Grain size decreases and the microstructure becomes more homogeneous with increasing Sb content in the Sn1-xSbxO2 samples from x = 0.01 to 0.05. The thermal conductivity and Seebeck coefficient of the Sb doped samples decreases with an increase in Sb concentration, while electrical conductivity increases up to a maximum at Sb doping level of x = 0.03 and then decreases at x = 0.05. The highest thermoelectric figure of merit of ZT ≈ 0.06 at 1073 K was exhibited by the sample of composition Sn0.99Sb0.01O2.

Influence of Sb incorporation on optical, electrical and gas sensing properties of transparent ZnO thin films

Polycrystalline nanostructured thin films of n-type ZnO and Sb doped ZnO with doping at 1%, 3% &5% possessing tailored electrical and optical properties are prepared by vacuum evaporation followed by air annealing and their application as gas sensor is evaluated. Doped films show substantial improvement in response time and sensitivity to Liquid Petroleum Gas, with fastest response ∼20 s for 5% Sb doped samples. Doping enhances optical bandgap, transmittance, photoresponse and electrical conductivity. Carrier concentration and mobility are maximum for 5% doped, which corroborates the electrical conductivity variations for the doped samples which is also maximum for 5% doped.

Niobium- and antimony-doped tin dioxide aerogels as new catalyst supports for PEM fuel cells

In order to tackle the problem of low durability, tin dioxide was studied to replace carbon black as a catalyst support in proton exchange membrane fuel cells (PEMFCs). SnO2 is a well-known n-type semi-conductor whose electronic conductivity can be improved by doping with hypervalent cations such as Nb5+ or Sb5+. In addition, as a catalyst support, this material has to develop a high specific surface area with an adequate mesoporous morphology to allow both good dispersion and activity of the catalyst (Pt). To this end, our objective was to develop doped SnO2 aerogels in order to gather in a same material both a high electronic conductivity and an adapted morphology. In this study, SnO2 xerogels and aerogels were successfully synthesized following an acid-catalyzed sol–gel route starting with metal alkoxides as precursors. Dried gels were calcined for 5 h at 600 °C in flowing air. The effect on both the structure and the morphology of the material resulting from doping with niobium or antimony was investigated by XRD, SEM, and nitrogen sorption. The electronic conductivity of pure and doped SnO2 materials was obtained from impedance spectroscopy and resistance measurements. Our materials showed a very interesting airy morphology adapted for the foreseen application: a reasonable specific surface area (80–90 m2/g) with a bimodal pore size distribution centered on around 25 and 45 nm. Moreover, all Sb-doped samples exhibited significant improvement in electronic conductivity. 5 at.% Sb-doped SnO2 even showed an electronic conductivity of 1 S/cm, very similar to that of Vulcan XC-72 (4 S/cm) and representing a 5 orders of magnitude increase compared to that of pure SnO2.

Phase Segregation and Superior Thermoelectric Properties of Mg2Si(1-x)Sb(x) (0 ≤ x ≤ 0.025) Prepared by Ultrafast Self-Propagating High-Temperature Synthesis.

A series of Sb-doped Mg2Si(1-x)Sb(x) compounds with the Sb content x within 0 ≤ x ≤ 0.025 were prepared by self-propagating high-temperature synthesis (SHS) combined with plasma activated sintering (PAS) method in less than 20 min. Thermodynamic parameters of the SHS process, such as adiabatic temperature, ignition temperature, combustion temperature, and propagation speed of the combustion wave, were determined for the first time. Nanoprecipitates were observed for the samples doped with Sb. Thermoelectric properties were characterized in the temperature range of 300-875 K. With the increasing content of Sb, the electrical conductivity σ rises markedly while the Seebeck coefficient α decreases, which is attributed to the increase in carrier concentration. The carrier mobility μ(H) decreases slightly with the increasing carrier concentration but remains larger than the Sb-doped samples prepared by other methods, which is ascribed to the self-purification process associated with the SHS synthesis. In spite of the increasing electrical conductivity with the increasing Sb content x, the overall thermal conductivity κ decreases on account of a significantly falled lattice thermal conductivity κ(L) due to the strong point defect scattering on Sb impurities and possibly enhanced interface scattering on nanoprecipitates. As a result, the sample with x = 0.02 achieves the thermoelectric figure of merit ZT ∼ 0.65 at 873 K, one of the highest values for the Sb-doped binary Mg2Si compounds investigated so far. A subsequent annealing treatment on the sample with x = 0.02 at 773 K for 7 days has resulted in no noticeble changes in the thermoelectric transport properties, indicating an excellent thermal stability of the compounds prepared by the SHS method. Therefore, SHS method can serve as an effective alternative fabrication route to synthesize Mg-Si based themoelectrics and some other functional materials due to the resulting high performance, perfect thermal stability, and feasible production in large scale for commercial application.

Sn02 Aerogels: Towards Performant and Stable PEFC Catalyst Supports

Keywords: Fuel Cells, Catalysts support, Metal oxides, Sol-gel, Aerogels. Carbon blacks supported Pt, currently widely used as electrocatalysts in Polymer Electrolyte Fuel Cells (PEFC) are thermochemically unstable in PEFC operating conditions. This is especially true at the cathode side where, on top of relatively elevated temperature (80°C) and acidic conditions, both the potential and the relative humidity may be high. The resulting carbon oxidation is partially responsible for the PEFC performance decrease observed over time. Hence, long term durability still needs to be improved in order to consider PEFC as credible alternatives to conventional power sources for automotive, stationary or portable applications. Tin dioxide has already been studied as an alternative catalyst support to replace carbon (1, 2). We will show how SnO2 aerogels may even be more promising candidates. Due to their remarkable nanotexturation, aerogels have indeed already proven their ability to efficiently support catalyst for PEMFC application (3). Our SnO2 aerogels were obtained from supercritical CO2 drying of gels synthetized following an acid catalyzed sol-gel route, starting from metal alkoxides precursors. Nb or Sb doping were realized adding the corresponding dopant alkoxide to the sol. The nanoscale morphology can be controlled during the sol-gel synthesis route and is retained after drying. The effect of doping with Nb5+ or Sb5+ on the structure and the morphology of the material was investigated by XRD, SEM and nitrogen sorption. Our materials showed reasonable specific surface areas (80-90 m²/g). The bimodal narrow pore size distribution, centered on around 25 and 45 nm after calcination at 600 °C, is particularly well adapted to the foreseen application. Such morphology (see Figure 1) was directed to i) favor both good dispersion and high activity of the catalyst (Pt) and ii) efficiently manage the water produced at the cathode during the oxygen reduction reaction (ORR). All Sb doped samples exhibited an impressive improvement of electronic conductivity, reaching 1 S/cm for 5 at.% Sb. This is representing a 5 orders of magnitude increase compared to pure SnO2. This level of conductivity is almost equivalent to that of carbon Vulcan XC-72R measured in the same conditions (4 S/cm). These properties make SnO2: Sb a very promising material as catalyst support for PEFC cathode. Our latest results, including platinum deposition and electrochemical activity, will be discussed with respect to the foreseen application. This work is funded by the FP7 NANOCAT European program (SP1-JTI-FCH.2012.1.5). REFERENCES 1. A. Masao, S. Noda, F. Takasaki, K. Ito, K. Sasaki, Carbon-Free Pt Electrocatalysts Supported on SnO2 for Polymer Electrolyte Fuel Cells. Electrochemical and Solid State Letters 12, B119-B122 (2009). 2. K. Kakinuma, M. Uchida, T. Kamino, H. Uchida, M. Watanabe, Synthesis and electrochemical characterization of Pt catalyst supported on Sn0.96Sb0.04O2-delta with a network structure. Electrochimica Acta 56, 2881-2887 (2011). 3. M. Ouattara-Brigaudet, C. Beauger, S. Berthon-Fabry, P. Achard, Carbon Aerogels as Catalyst Supports and First Insights on Their Durability in Proton Exchange Membrane Fuel Cells. Fuel Cells 11, 726-734 (2011). Figure 1

Numeral description of grain size effects of tin oxide gas-sensitive elements and evaluation of depletion layer width

The grain size effects on tin oxide gas-sensitive elements are numerically described by the model of gradient-distributed oxygen vacancies, which extends the receptor function of semiconductors to the condition of inhomogeneous donor density in grains. The sensor resistance and the response to the reducing gas are formulated as functions of the grain size and the depletion layer width. The simulations show good agreement with the experimental results. The depletion layer width is estimated as 4 nm for the undoped SnO2 element, whereas the values are 2 and 7 nm for Sb-doped and Al-doped samples, respectively. The results are experimentally verified by the donor-doped SnO2 thin films, the depletion layer widths of which are evaluated on the basis of the correlation between the electrical resistance and the Sb-doping amount. The location of the Fermi level is found to be a crucial factor that dominates the evaluation results. Open image in new window

Effects of Sb oxidation state on the densification and electrical properties of antimony-doped tin oxide ceramics

For antimony-doped tin oxide (ATO), Sb content and oxidation state remarkably influence the densification, microstructure and electrical properties of ATO ceramics. In this work, ATO powders doped with Sb(III) or Sb(V) are prepared via chemical precipitation method and are then consolidated by spark plasma sintering (SPS). Results demonstrate that ATO ceramics with a small content of nanoscaled antimony oxides, either Sb(III) or Sb(V), can be densified through the rapid SPS process. The relative density of 1.5 mol% Sb-doped samples is greater than 96.5 %. However, increased Sb doping concentration, especially for Sb(V), restrains both the densification and grain growth in SPS-consolidated ATO. In contrast, Sb(V)-doped material exhibits improved electrical conductivity. The resistivity of 1.5 mol% Sb(V)-doped sample is only 0.01699 Ω cm, far lower than that of the 1.5 mol% Sb(III)-doped sample (0.1338 Ω cm). XPS results indicate a higher Sb5+/Sb3+ ratio in Sb(V)-doped ATO powder and ceramic than in Sb(III)-doped samples. The higher Sb5+/Sb3+ ratio contributes to the increase of carrier concentration and the decrease of resistivity of ATO ceramics.

Multiscale microstructures and improved thermoelectric performance of Mg2(Si0.4Sn0.6)Sbx solid solutions

A series of Sb -doped Mg 2( Si 0.4 Sn 0.6) Sb x (0 ≤ x ≤ 0.025) solid solutions were prepared by an induction melting, Melt Spinning (MS) and Spark Plasma Sintering (SPS) method, namely the non-equilibrium technique MS–SPS, using bulks of Magnesium, Silicon, Tin, and Antimony as raw materials. The non-equilibrium technique generates the unique multiscale microstructures of samples containing micronscale grains and nanoscale precipitates, the multiscale microstructures remarkably make the lattice thermal conductivities decreased, particularly for samples with the nanoscale precipitates having the size of 10–20 nm. Meanwhile, Sb -doping greatly increased the electrical performance of samples. Consequently, the Sb -doping combined with the multiscale microstructures strategy remarkably improves the overall thermoelectric (TE) performance of Sb doped samples, and a high dimensionless figure of merit (ZT) value of up to 1.25 at 723 K is obtained with Mg 2( Si 0.4 Sn 0.6) Sb 0.02 sample in a relatively wide temperature range.

Microstructure and Ionic Conductivity of Sb-doped Li7La3Zr2O12 Ceramics

The garnet-related oxides Li7-xLa3Zr2-xSbxO12 (x = 0, 0.075) were prepared by solid-state reaction method. Crystal structure, microstructure, conductivity, and element distribution were characterized for the pure and Sb-doped Li7La3Zr2O12. Ionic conductivity of the Li7La3Zr2O12 is enhanced by Sb doping. An amorphous Li-La-Zr-Al-O thin film which is formed on the grain boundary of Sb-doped samples not only suppresses the abnormal grain growth but also eliminates the pores on the grain boundary. The ionic conductivity of Sb doped Li7-xLa3Zr2-xSbxO12 ceramic with x = 0.075 sintered at 1160°C reaches about 3.40×10 S/cm.

Tunable microstructures and improved thermoelectric performance of Mg2(Si0.4−xSbxSn0.6) solid solutions

The single-phase n-type Mg2(Si0.4−xSbxSn0.6) (0≤x≤0.025) solid solutions were prepared by an induction melting and Spark Plasma Sintering method using buck of Magnesium, Silicon, Tin and Antimony. The unique multiple nanostructures of samples containing nanoscale precipitates and mesoscale grains are formed by the non-equilibrium preparing technique, resulting in remarkably decreasing of lattice thermal conductivities, particularly for samples with the nanoscale precipitates having the size of 20–30nm. Meanwhile, the electrical properties were increased by Sb-doping. The thermoelectric performance of Sb doped samples with the nanostructures are remarkably improved, and the dimensionless figure of ZT for Mg2(Si0.38Sb0.02Sn0.6) sample shows highest value of 1.30 at 773K, which is very much higher than that of the non-doped sample.

Fabrication parameters for optimized thermoelectric Mg2Si

Here, we report on the effect of sintering temperature, particle size, and sintering pressure on the thermoelectric properties of Sb-doped Mg2Si samples. We find a strong dependence of thermoelectric performance on sintering temperature with the best properties achieved at 900 °C. We furthermore show a strong influence of the particle size of the employed powder, with coarser powder giving better properties. The difference stems mainly from the electrical conductivity; Seebeck coefficient and thermal conductivity are affected to a lesser extent. With respect to sintering pressure, a small positive influence of increasing pressure is found. We obtain a peak thermoelectric figure of merit of 0.75 ± 0.18 at 820 K employing optimized fabrication parameters.

A Comparison Between the Effects of Sb and Bi Doping on the Thermoelectric Properties of the Ti0.3Zr0.35Hf0.35NiSn Half-Heusler Alloy

We deal here with Sb and Bi doping effects of the n-type half-Heusler (HH) Ti0.3Zr0.35Hf0.35NiSn alloy on the measured thermoelectric properties. To date, the thermoelectric effects upon Bi doping on the Sn site of HH alloys have rarely been reported, while Sb has been widely used as a donor dopant. A comparison between the measured transport properties following arc melting and spark plasma sintering of both Bi- and Sb-doped samples indicates a much stronger doping effect upon Sb doping, an effect which was explained thermodynamically. Due to similar lattice thermal conductivity values obtained for the various doped samples, synthesized in a similar experimental route, no practical variations in the thermoelectric figure of merit values were observed between the various investigated samples, an effect which was attributed to compensation between the power factor and electrical thermal conductivity values regardless of the various investigated dopants and doping levels.