• Korean Journal of Materials Research
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• v.22 no.7
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• pp.358-361
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• 2012

Co and Ni as catalysts in $SnO_2$ sensors to improve the sensitivity for $CH_4$ gas and $CH_3CH_2CH_3$ gas were coated by a solution reduction method. $SnO_2$ thick films were prepared by a screen-printing method onto $Al_2O_3$ substrates with an electrode. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a chamber. The structural properties of $SnO_2$ with a rutile structure investigated by XRD showed a (110) dominant $SnO_2$ peak. The particle size of the $SnO_2$:Ni powders with Ni at 6 wt% was about 0.1 ${\mu}m$. The $SnO_2$ particles were found to contain many pores according to a SEM analysis. The sensitivity of $SnO_2$-based sensors was measured for 5 ppm of $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air to that in the target gases. The results showed that the best sensitivity of $SnO_2$:Ni and $SnO_2$:Co sensors for $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature was observed in $SnO_2$:Ni sensors coated with 6 wt% Ni. The $SnO_2$:Ni gas sensors showed good selectivity to $CH_4$ gas. The response time and recovery time of the $SnO_2$:Ni gas sensors for the $CH_4$ and $CH_3CH_2CH_3$ gases were 20 seconds and 9 seconds, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.245-250
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• 2019

We investigated the post-annealing effect of Sn-incorporated β-Ga₂O₃ (β-Ga₂O₃ : Sn) nanowires (NWs) grown on sapphire (0001) substrates using radio-frequency powder sputtering. The β-Ga₂O₃ : Sn NWs were converted to a porous structure during the vacuum annealing process at 800℃. Host non-stoichiometric Ga₂O_3-x, is transformed into stoichiometric Ga₂O₃, where Sn atoms separate and form Sn nano-clusters that gradually evaporate in a vacuum atmosphere. As a result, the amount of Sn atoms was reduced from 1.31 to 0.27 at%. Pores formed on the sides of β-Ga₂O₃ : Sn NWs were observed. This increases the ratio of the surface to the volume of β-Ga₂O₃ : Sn NWs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.276-283
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• 1997

A dry impregnation method was used for preparing pellet type Pt/$SnO_2$ gas sensor. The crystal structure, direction of the crystal, crystal size and microstructure between the catalyst and the support ($SnO_2$) were characterized with electron diffraction analysis, transmission electron microscopy, scanning electron microscopy. The characterization indicates that when Pt/$SnO_2$ sample is calcined at $400^{\circ}C$, the Cl content associated with the Pt phase diminishes and the part of Pt is moved into $SnO_2$ support. This results in the enhancement of gas sensitivity. After the reactor with a Pt/$SnO_2$ sample was run with a flow rate of 30 sccm (a mixture of 0.5% $H_2$ in $_N2$) for a while, the resistance of $SnO_2$ was saturated, but the $SnO_2$ kept absorbing $H_2$ gas. This indicates that the surface state was saturated. For the 14 ppm $H_2$ gas, the sensitivity of Pt/$SnO_2$ devices was about 81% at an operating temperature of $300^{\circ}C$.

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.408-411
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• 2010

Indium doped $SnO_2$ thick films for gas sensors were fabricated by a screen printing method on alumina substrates. The effects of indium concentration on the structural and morphological properties of the $SnO_2$ were investigated by X-ray diffraction and Scanning Electron Microscope. The structural properties of the $SnO_2$:In by X-ray diffraction showed a (110) dominant $SnO_2$ peak. The size of $SnO_2$ particles ranged from 0.05 to $0.1\;{\mu}m$, and $SnO_2$ particles were found to contain many pores, according to the SEM analysis. The thickness of the indium-doped $SnO_2$ thick films for gas sensors was about $20\;{\mu}m$, as confirmed by cross sectional SEM image. Sensitivity of the $SnO_2$:In gas sensor to 2000 ppm of $CO_2$ gas and 50 ppm of H2S gas was investigated for various indium concentrations. The highest sensitivity to $CO_2$ gas and H2S gas of the indium-doped $SnO_2$ thick films was observed at the 8 wt% and 4 wt% indium concentration, respectively. The good sensing performances of indium-doped $SnO_2$ gas sensors to $CO_2$ gas were attributed to the increase of oxygen vacancies and surface area in the $SnO_2$:In. The $SnO_2$:In gas sensors showed good selectivity to $CO_2$ gas.

• Journal of Sensor Science and Technology
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• v.11 no.3
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• pp.155-162
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• 2002

The sensing properties of carbon monooxide were investigated as a function of mixing ratio and the lamination structure of 3mol% ZnO-doped $SnO_2$ and 3mol% $SnO_2$-doped ZnO. The lamination structures were fabricared monolayer, double layer, and hetero layer of $SnO_2$, Zno, and theirs mixture composition using thick film process. There was no second phase by the reaction of $SnO_2$ and ZnO. The conductance was decreased by the addition of ZnO in $SnO_2$, but it was increased with the addition of $SnO_2$ in ZnO. The conductance was increased with temperature and the inlet of CO. There was no improvement of sensitivity in the structure of mono- and double-layer. The hetero-layer structure, however, of $SnO_2$ 3ZnO-ZnO $3SnO_2$ showed the higher resistivity and the highest sensitivity. Ohmic characteristics was confirmed by the linear properties for I-V measurements.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1084-1089
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• 2010

This study elucidates the formation mechanism of SnO plate observed during the precipitation reaction of a $SnCl_2$ aqueous solution. $Sn_{21}Cl_{16}(OH)_{14}O_6$ and $Sn_6O_4(OH)_4$ precipitates was formed at pH=3~5 and at pH=11, respectively. When the pH was in the range of 11.5~12.5, the $Sn_6O_4(OH)_4$ precipitates dissolved into $HSnO_2{^-}[Sn_6O_4(OH)_4+4OH^-={6HSnO_2{^-}+2H^+]$ and dissolved $HSnO_2{^-}$ ions reprecipitated to SnO plate $[HSnO_2{^-}+H^+=SnO+H_2O]$. The $Sn_6O_4(OH)_4$ precipitates completely transformed into SnO plate through a repeated process of dissolution-precipitation in the range of pH=11.5~12.5.

• Industry Promotion Research
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• v.3 no.1
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• pp.1-5
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• 2018

$SnO_2$ films were annealed in a vaccum atmosphere conditions to research the temperature dependency of current-voltage characteristics in according to the bonding structures. The $SnO_2$ film annealed in a vacuum became an amorphous structure but films annealed in an atmosphere condition had a crystal structure. The defects or depletion layer were formed by the electron-hole combination after annealing processes, and the electrical properties were changed depending on the crystal structure, binding energy and the variation of carriers. $SnO_2$ became more crystal-structural with increasing the annealing temperature, and the current increased at $SnO_2$ film annealed at $150^{\circ}C$ with Schottky current.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.1 s.34
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• pp.35-40
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• 2005

The oxidation of pure Sn and Sn-0.7Cu, Sn-3.5Ag, Sn-lZn, and Sn-9Zn alloys at $150^{\circ}C$ was investigated. Both the chemical nature and the amount of oxides were characterized using electrochemical reduction analysis by measuring the electrolytic reduction potential and total transferred electrical charges. X-ray photoelectron spectroscopy (XPS) was also conducted to support the results of reduction analysis. The effect of Cu, Ag and Zn addition on surface oxidation of Sn alloys is reported. For Sn, Sn-0.7Cu and Sn-3.5Ag, SnO grew first and then the mixture of SnO and $SnO_2$ was found. $SnO_2$ grew predominantly for a long-time aging. For Zn containing Sn alloys, both ZnO and $SnO_2$ were formed. Zn promotes the formation of $SnO_2$. Sn oxide growth rate of Pb-free solder alloys was also discussed in terms of alloying elements.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1912-1920
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• 2011

The $SnO_2$ with a particle size of about 300 nm instead of Ni is used in this study to overcome rapid catalytic deactivation by the formation of a $NiAl_2O_4$ spinal structure on the conventional Ni/${\gamma}$-$Al_2O_3$ catalyst and simultaneously impregnated the catalyst with potassium (K). The $SnO_2-K_2O$ impregnated Zeolite Y catalyst ($SnO_2-K_2O$/ZY) exhibited significantly higher ethanol reforming reactivity that that achieved with $SnO_2$ 100 and $SnO_2$ 30 wt %/ZY catalysts. The main products from ethanol steam reforming (ESR) over the $SnO_2$-$K_2O$/ZY catalyst were $H_2$, $CO_2$, and $CH_4$, with no evidence of any CO molecule formation. The $H_2$ production and ethanol conversion were maximized at 89% and 100%, respectively, over $SnO_2$ 30 wt %-$K_2O$ 3.0 wt %/ZY at 600 $^{\circ}C$ for 1 h at a $CH_3CH_2OH:H_2O$ ratio of 1:1 and a gas hourly space velocity (GHSV) of 12,700 $h^{-1}$. No catalytic deactivation occurred for up to 73 h. This result is attributable to the easier and weaker of reduction of Sn components and acidities over $SnO_2-K_2O$/ZY catalyst, respectively, than those of Ni/${\gamma}$-$Al_2O_3$ catalysts.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.865-868
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• 2002

$SnO_2$ powders were prepare by precipitating $Sn(OH)_4$ from an aqueous solution of $SnCl_4{\cdot}5H_2O$, pH 9.5. The effects of stability and sensitivity of $SnO_2$ thick film sensors added with various amounts, $SiO_2$, $Al_2O_3$, $ZrO_2$, $TiO_2$ have been investigated. It is shown that the 3wt% $Al_2O_3$ or $SiO_2$ can improve the stability of $SnO_2$ gas sensor at an operating temperature of $350^{\circ}C$.