Journal of Nanomaterials
Volume 2015 (2015), Article ID 979543, 8 pages
http://dx.doi.org/10.1155/2015/979543

Research Article

CO and C₃H₈ Sensitivity Behavior of Zinc Antimonate Prepared by a Microwave-Assisted Solution Method

Héctor Guillen-Bonilla,¹ Verónica-M. Rodríguez-Betancourtt,¹ José-Trinidad Guillén-Bonilla,² Juan Reyes-Gómez,³ Lorenzo Gildo-Ortiz,³ Martín Flores-Martínez,¹ M. de la L. Olvera-Amador,⁴ and Jaime Santoyo-Salazar⁵

¹Departamento de Ingeniería de Proyectos, CUCEI, Universidad de Guadalajara, 44410 Guadalajara, JAL, Mexico
²Departamento de Electrónica y Computación, CUCEI, Universidad de Guadalajara, 44410 Guadalajara, JAL, Mexico
³Facultad de Ciencias, Universidad de Colima, 28045 Colima, COL, Mexico
⁴Departamento de Ingeniería Eléctrica-SEES, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, 07360 México, DF, Mexico
⁵Departamento de Física, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, 07360 México, DF, Mexico

Received 21 September 2015; Accepted 1 December 2015

Academic Editor: Hassan Karimi-Maleh

Copyright © 2015 Héctor Guillen-Bonilla et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

ZnSb₂O₆ has been synthesized by a microwave-assisted solution method in order to test its possible application as a gas sensor. Zinc nitrate, antimony trichloride, and ethylenediamine were used as precursors and deionized water as solvent. Microwave radiation, with a power of ~350 W, was applied for solvent evaporation. The thermal decomposition of the precursors leads to the formation of ZnSb₂O₆ at 600°C. This oxide crystallized in a tetragonal structure with cell parameters  Å,  Å and space group P4₂/mnm. Microwires and microrods formed by nanocrystals were observed by means of scanning and transmission electron microscopies (SEM and TEM, resp.). Pellets of the oxide were tested as gas sensors in flowing atmospheres of carbon monoxide (CO) and propane (C₃H₈). Sensitivity increased with the gas concentration (0–300 ppm) and working temperatures (ambient, 150 and 250°C) increase. The results indicate high sensitivity of ZnSb₂O₆ in both gases at different concentrations and operating temperatures.

1. Introduction

The need of reliable detection devices for dangerous atmospheres has promoted a huge research since past decades on the development of semiconductor materials suitable as gas sensors. In general, the gas sensors are used in domestic applications and industrial processes like monitoring of automobile exhaust gases, flue-gases in incinerators, the possible toxicity in the air, and so forth [1–5]. Important criteria for the fabrication of these sensors are low price, chemical stability, selectivity, and very good sensitivity [6, 7]. Among all semiconductors that can be used as sensors, the binary oxide SnO₂ is regarded as one of the most promising materials for such purpose [8–11], because it possesses some of the above desired features, like high sensitivity and chemical stability [12–14]. However, some other semiconductor types, with more complex crystal structures, are currently investigated, like the ones with perovskite structure: , SmFeO₃, and SrFeO₃ [15–17]; spinel structure: MgAl₂O₄, CdCr₂O₄, and ZnFe₂O₄ [18–20]; and oxides with trirutile-type structure: CoTa₂O₆, NiTa₂O₆, and CoSb₂O₆ [21–23]. Among the latter, the type-n semiconductor zinc antimonate ZnSb₂O₆ has been extensively studied for gas sensing applications due to its high response to several toxic gases [24]. Our work presented here is devoted to such material.

Michel et al. [25] synthesized ZnSb₂O₆ through a colloidal method and probed its sensing capabilities in O₂, CO, and CO₂ atmospheres by means of dynamic tests using frequencies from 0.1 to 100 kHz at a temperature of 400°C. Their results showed good selectivity, reproducibility, and chemical stability. Tamaki et al. [26] prepared thick films of ZnSb₂O₆ through a dip-coating method, obtaining good selectivity and stability in H₂S atmospheres, attributing this to the film’s porous structure.

Generally speaking, the zinc antimonate adopts a formula ASb₂O₆, where A can be substituted by the divalent Zn ion or the ions Ni, Co, Mg, and Cu, among others [27]. This oxide belongs to the family of trirutile-type materials and crystallizes in a tetragonal structure with a space group P4₂/mnm [28]. In general, the trirutile-type materials are synthesized by a ceramic-method [29] but ZnSb₂O₆ has been better prepared by a colloidal-route [25]. In our work, we synthesized the oxide through a microwave-assisted solution-method and prepared pellets with it in order to test its sensing capabilities in CO and C₃H₈ atmospheres at relative low temperatures.

2. Experimental Procedures

2.1. Synthesis of ZnSb₂O₆

We synthesized ZnSb₂O₆ preparing three solutions: 1.48 g (0.005 mol) of Zn(NO₃)₂·6H₂O (J. T. Baker), 2.28 g (0.01 mol) of SbCl₃ (Sigma-Aldrich), and 0.5 mL of ethylenediamine (Sigma), dissolving each separately in 5 mL of distilled water. The solutions were magnetically stirred at 350 rpm during 20 min. After that, the antimony chloride and ethylenediamine solutions were mixed under stirring. The zinc nitrate solution was next slowly poured to the mixed solution under stirring at 350 rpm during 24 h. After this, the solvent was evaporated by means of fourteen 180 s-microwave-exposures at ~350 W (General Electric microwave oven, model JES769WK; the absorbed energy was estimated to 863 kJ), recording a temperature of ~92°C after each exposure. Temperature and exposure time were controlled in order to avoid material loss by splashing. After the evaporation, the product was heated at 200°C during 8 h and afterward calcined in air at 600°C during 5 h with a heat rate of 100°C/h using a temperature-controlled oven (Vulcan 3-550).

2.2. Physical Characterization of ZnSb₂O₆ Powders

The synthesized zinc antimonate (ZnSb₂O₆) powders were analyzed by means of X-ray diffraction (Siemens D 500 XRD-system, CuKα radiation, 2θ scanning-angle from 10 to 70° and 1-second steps of 0.02°). The powders were analyzed by Raman spectroscopy using a 1000B microRaman Renishaw system, calibrated with a silicon semiconductor with its characteristic Raman peak at 520 cm⁻¹. The laser (excitation wavelength of 830 nm) was focused on the surface of the powders (spot size of approximately 20 μm) by means of a Leica optical microscope (DMLM) integrated to the microRaman system. The radiation energy on the sample was 4.5 mW during 60 s. The microstructure was analyzed by means of scanning electron microscopy (JEOL JSM-6390LV SEM-system, in high-vacuum mode, using secondary-electron-emission) and a dispersion in isopropyl alcohol of the powders was put in a copper grid and analyzed by means of transmission electron microscopy (JEOL JEM-2010 TEM-system, at a 200 kV accelerating voltage).

2.3. Pellets Preparation for Gas Sensitivity Analysis

For the sensitivity studies, pellets from the calcined powders were prepared using 0.353 g of them and compressed by means of a 25-ton manual-pressing-equipment (SIMPLEX ITAL EQUIP). The best pressing parameters were 20 tons during 120 min, obtaining pellets with a diameter of 12 mm, and a thickness of 500 μm.

The pellets of ZnSb₂O₆, with a thickness of 500 μm, were exposed to carbon monoxide (CO) and propane (C₃H₈) flows at concentrations 5, 50, 100, 200, and 300 ppm of both gases. Working temperatures were 23°C (ambient), 150°C, and 250°C. The sensitivity changes () were evaluated using [30–32]

where and are electrical conductance of the ZnSb₂O₆ pellets measured in gas (CO or C₃H₈) and air, respectively.

For this analysis, a measuring vacuum chamber with a vacuum capacity of 10⁻³ Torr was used. Gas concentration and partial pressure were controlled using a TM20 Leybold detector. Electric resistance measures were carried out by means of a digital multimeter (model Keithley 2001). See Figure 1.

Figure 1: Experimental array for the sensitivity testing of ZnSb₂O₆.

3. Results and Discussion

3.1. XRD Analysis

Figure 2 shows a diffractogram depicting the zinc antimonate (ZnSb₂O₆) oxide’s peaks corresponding to the different crystal planes, which were identified by means of the JCPDF file 38-0453. It was found that the oxide exhibits a tetragonal crystal structure with cell parameters  Å,  Å and a P4₂/mnm spatial group. That means the oxide is a trirutile phase type [24, 26, 33, 34], which agrees with the results in [35, 36]. Furthermore, the small peaks at 2θ = 29.62°, 42.54°, and 60.61° belong to the secondary phase ZnSb₂O₄ [25], which were identified through the JCPDF file 15-0802.

Figure 2: Diffractogram of the zinc antimonate (ZnSb₂O₆) powders calcined at 600°C in air.

In previous works, the ZnSb₂O₆ oxide has been prepared through different synthesis routes, obtaining the oxide generally above a temperature of 600°C. For example, Wu et al. [37] prepared the oxide by means of a solid-state-reaction, mixing ZnO and Sb₂O₃ at 700–1000°C, and Zhu et al. [38] used the vapor-phase-oxidation method in a Ar + O₂ atmosphere at a temperature between 500 and 900°C. In the present work, the synthesis of the oxide by means of a microwave-assisted solution method was done at a temperature of 600°C, which brings some advantages against the previously cited works.

3.2. Raman Spectroscopy Analysis

The Raman spectrum of the oxide is depicted in Figure 3, where the main bands to , in the range 500–800 cm⁻¹, correspond to the vibration of the Sb₂O₁₀ units of the oxide’s crystals, and the weaker bands to , which are below 400 cm⁻¹, are due to the influence of Zn²⁺. In more detail, in the range 600–800 cm⁻¹, the stretching modes of the Sb– bonds predominate, while in the range 400–500 cm⁻¹, the deformation modes of the Sb– bonds, coupled to the vibrations of the Zn–O bonds, are dominant. The 500–600 cm⁻¹ bands are due to the elongation modes of the Sb– bonds [39, 40]. This analysis supports the results obtained by XRD, shown above.

Figure 3: Raman spectrum of the ZnSb₂O₆ powders calcined at 600°C in air.

3.3. Scanning Electron Microscopy Analysis

Figure 4 shows three typical SEM photomicrographs of trirutile-type zinc antimonate (ZnSb₂O₆) powders after calcination at 600°C. These images present three different magnifications: 100x, 500x, and 1500x.

(a)

(b)

(c)

Figure 4: SEM images of trirutile-type zinc antimonate (ZnSb₂O₆) powders calcined at 600°C at different magnifications: (a) 100x, (b) 500x, and (c) 1500x.

A dendrite-like formation of microwires and microrods is depicted in Figure 4(a), at 100x (see the inserted zoom), which can be due to the rise of the temperature during the calcinations, the lasted time by the material in the muffle, and the ethylenediamine concentration [41]. About the latter, the ethylenediamine incorporates into the organic frame and then escapes as a result of the thermal treatment, giving rise to the desired morphologies, like those obtained in this work. The importance of ethylenediamine in the formation of nano- and microstructures has been discussed in previous works [42, 43]. In our case, the microrod’s length was estimated in the range 10–100 μm with a standard deviation of 21.3 μm and an average of 59.5 μm. The averaged diameter was of 1.5 μm (see Figure 4(b)). As can be observed, tiny crystals (average size of 1.1 μm) agglomerate to give shape to the microrods. At 1500x (Figure 4(c)), more details of the microstructure can be seen, where a porous surface and the strong agglomeration of individual particles, with irregular shape, are clearly discernible. The agglomeration is due to the formation of necks caused by the elimination of organic material after the thermal treatment. The porosity is attributed to the release of gases during the thermal decomposition, mainly water vapor, , and CO₂ [31, 44].

3.4. Transmission Electron Microscopy Analysis

Figure 5 shows typical images obtained by transmission electron microscopy. In Figures 5(a) and 5(b) photomicrographs of the microrods formed by the tiny cubic-shaped crystals can be observed. The analyzed microrod in Figure 5(a) had a length of 6.6 μm and a diameter of 0.857 μm, while the tiny crystal’s size was around 50–250 nm (Figure 5(b)). High resolution transmission electron microscopy (HRTEM) was performed in a selected zone of the sample (Figures 5(b) and 5(c)). The HRTEM image reveals that the interplanar distance is around 0.46 nm, which corresponds to (002) planes. In order to verify the local crystallinity of the sample, selected area electron diffraction (SAED) was made on several rods. The inset in Figure 5(b) shows a typical pattern; these results confirmed the crystallinity of the sample previously registered in XRD analysis.

Figure 5: TEM analysis of trirutile-type zinc antimonate (ZnSb₂O₆) powders (600°C): ((a), (b)) microrods formed by crystals, (c) HRTEM image showing the lattice fringes.

3.5. Sensing Properties

The variations of the sensitivity’s magnitude are shown in Figures 6(a)–6(c) in carbon monoxide (CO) atmospheres.

(a)

(b)

(c)

Figure 6: Sensitivity of ZnSb₂O₆ pellets as a function of (a) CO concentration and (b) CO operating temperature; (c) maximum values of at 250°C for every CO concentration.

These results show that ZnSb₂O₆ is highly sensitive to the employed CO concentrations and to operation temperatures above 150°C. No significant variations below such temperature were found. The maximum value of the sensitivity was of ~6.66 for a concentration of 300 ppm at 250°C. The increase of the sensitivities with the concentration is due to the raise of the number of gas molecules, which react with the adsorbed oxygen, donating electrons to the material’s surface [31, 45]. The most accepted mechanism to explain this is a model based on the depletion layer’s modulation due to the oxygen adsorption [8, 11, 14]. In this model [14], the adsorbed oxygen on the semiconductor’s surface ionizes to O⁻ and O²⁻, diminishing consequently the carriers concentration and the electrons’ mobility, because these species are more reactive than others (like , which is not produced or is detected because the thermal energy is not enough for that) at temperatures above 150°C [46]. ZnSb₂O₆ strongly reacts above such temperature with CO [31, 32] of the atmosphere yielding CO₂ and releasing electrons back into the conduction band [25, 47], especially at the temperature of 250°C, producing a high sensitivity.

A similar trend was found for different propane concentrations and operation temperatures (Figures 7(a)–7(c)). As expected, at ambient temperature (23°C) no variation of the sensitivity was detected, but when the temperature was increased, sensitivity variations were observed. The maximum was at 250°C for a propane concentration of 300 ppm. A mechanism to explain the propane detection at relative low temperatures, like 250°C or 350°C, has not been yet reported. Other investigations, using similar semiconductor oxides (like SnO₂ and ZnO) to detect propane, report a maximum sensitivity of ~0.7 and ~0.6 for a propane concentration of 500 ppm at 300°C [48, 49]. Comparatively, we obtained better results here. In addition, we have found in previous works, using a cobalt oxide in the same atmospheres, that a trirutile-type structure, like that of the oxide of this work, is highly responsible for a great performance and excellent stability [32].

(a)

(b)

(c)

Figure 7: Sensitivity of ZnSb₂O₆ pellets as a function of (a) propane (C₃H₈) concentration and (b) operating temperature; (c) maximum values of at 250°C at different propane concentrations.

4. Conclusions

Zinc antimonate (ZnSb₂O₆), with a trirutile-type structure, forming microstructures like microrods and microwires and intended to be used for gas sensing applications, was successfully synthesized employing a microwave-assisted solution-method at relative low temperatures. Tested pellets of ZnSb₂O₆ were clearly sensitive and uniform in response to the operating temperatures and gas concentrations in carbon monoxide (CO) and propane (C₃H₈) atmospheres. A good sensitivity was obtained at 250°C, with a maximum (CO) and (C₃H₈) at 300 ppm. It has been found that ZnSb₂O₆ is a strong candidate for being applied as an environmental gas sensor.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgments

Héctor Guillen-Bonilla acknowledges Mexico’s Consejo Nacional de Ciencia y Tecnología (CONACyT) for the received financial support. The technical support received from Darío Pozas Zepeda and Miguel Ángel Luna Arias is also appreciated. This work was partially supported by Project no. 263656 from CONACyT, Project no. 254790 from CONACyT, and Project no. 784-12 FRABA.

References

M. Fleischer and H. Meixner, “Fast gas sensors based on metal oxides which are stable at high temperatures,” Sensors and Actuators B: Chemical, vol. 43, no. 1–3, pp. 1–10, 1997.

N. D. Hoa, N. V. Duy, S. A. El-Safty, and N. V. Hieu, “Meso-/nanoporous semiconducting metal oxides for gas sensor applications,” Journal of Nanomaterials, vol. 2015, Article ID 972025, 14 pages, 2015.

C. J. Belle, A. Bonamin, U. Simon et al., “Size dependent gas sensing properties of spinel iron oxide nanoparticles,” Sensors and Actuators, B, vol. 160, no. 1, pp. 942–950, 2011.

K. Arshak and I. Gaidan, “Development of a novel gas sensor based on oxide thick films,” Materials Science and Engineering: B, vol. 118, no. 1–3, pp. 44–49, 2005.

W. Chen, H. Gan, W. Zhang, and Z. Mao, “Hydrothermal synthesis and hydrogen sensing properties of nanostructured SnO₂ with different morphologies,” Journal of Nanomaterials, vol. 2014, Article ID 291273, 7 pages, 2014.

M.-I. Baraton and L. Merhari, “Electrical behavior of semiconducting nanopowders versus environment,” Reviews on Advanced Materials Science, vol. 4, no. 1, pp. 15–24, 2003.

N. Yamazoe, “Toward innovations of gas sensor technology,” Sensors and Actuators B: Chemical, vol. 108, no. 1-2, pp. 2–14, 2005.

G. Sberveglieri, “Recent developments in semiconducting thin-film gas sensors,” Sensors and Actuators B: Chemical, vol. 23, no. 2-3, pp. 103–109, 1995.

A. Licciulli, S. Mazzarelli, G. De, P. Siciliano, L. Vasanelli, and R. Rella, “Os and Pd modified tin oxide films for sensors by the sol gel process,” Journal of Sol-Gel Science and Technology, vol. 21, no. 3, pp. 195–201, 2001.

S. Nicoletti, L. Dori, F. Corticelli, M. Leoni, and P. Scardi, “Tin oxide thin-film sensors for aromatic hydrocarbons detection: effect of aging time on film microstructure,” Journal of the American Ceramic Society, vol. 82, no. 5, pp. 1201–1206, 1999.

M. Hübner, C. E. Simion, A. Haensch, N. Barsan, and U. Weimar, “CO sensing mechanism with WO₃ based gas sensors,” Sensors and Actuators, B: Chemical, vol. 151, no. 1, pp. 103–106, 2010.

G. Martinelli and M. C. Carotta, “Thick-film gas sensors,” Sensors and Actuators B: Chemical, vol. 23, no. 2-3, pp. 157–161, 1995.

M. Yuasa, T. Masaki, T. Kida, K. Shimanoe, and N. Yamazoe, “Nano-sized PdO loaded SnO₂ nanoparticles by reverse micelle method for highly sensitive CO gas sensor,” Sensors and Actuators B: Chemical, vol. 136, no. 1, pp. 99–104, 2009.

T. Zhang, L. Liu, Q. Qi, S. Li, and G. Lu, “Development of microstructure In/Pd-doped SnO₂ sensor for low-level CO detection,” Sensors and Actuators B: Chemical, vol. 139, no. 2, pp. 287–291, 2009.

L. Jingbo, L. Wenchao, Z. Yanxi, and W. Zhimin, “Preparation and characterization of Li⁺-modified film for humidity sensor,” Sensors and Actuators B: Chemical, vol. 75, no. 1-2, pp. 11–17, 2001.

M. C. Carotta, G. Martinelli, Y. Sadaoka, P. Nunziante, and E. Traversa, “Gas-sensitive electrical properties of perovskite-type SmFeO₃ thick films,” Sensors and Actuators B: Chemical, vol. 48, no. 1-3, pp. 270–276, 1998.

Y. Wang, J. Chen, and X. Wu, “Preparation and gas-sensing properties of perovskite-type SrFeO₃ oxide,” Materials Letters, vol. 49, no. 6, pp. 361–364, 2001.

V. Coillard, H. Debéda, C. Lucat, and F. Ménil, “Nitrogen monoxide detection with a planar spinel coated amperometric sensor,” Sensors and Actuators B, vol. 78, no. 1–3, pp. 113–118, 2001.

G. Lu, N. Miura, and N. Yamazoe, “A high temperature amperometric NO sensor based on stabilized zirconia and CdCr₂O₄ electrode,” Journal of Applied Electrochemistry, vol. 28, no. 9, pp. 1009–1011, 1998.

Y. Shimizu, S. Kusano, H. Kuwayama, K. Tanaka, and M. Egashira, “Oxygen-sensing properties of spinel-type oxides for stoichiometric air/fuel combustion control,” Journal of the American Ceramic Society, vol. 73, no. 4, pp. 818–824, 1990.

P. T. Moseley, D. E. Williams, J. O. W. Norris, and B. C. Tofield, “Electrical conductivity and gas sensitivity of some transition metal tantalates,” Sensors and Actuators, vol. 14, no. 1, pp. 79–91, 1988.

C. R. Michel, H. Guillén-Bonilla, A. H. Martínez-Preciado, and J. P. Morán-Lázaro, “Synthesis and gas sensing properties of nanostructured CoSb₂O₆ microspheres,” Sensors and Actuators B: Chemical, vol. 143, no. 1, pp. 278–285, 2009.

A. Guillén-Bonilla, V.-M. Rodríguez-Betancourtt, M. Flores-Martínez et al., “Dynamic response of CoSb₂O₆ trirutile-type oxides in a CO₂ atmosphere at low-temperatures,” Sensors, vol. 14, no. 9, pp. 15802–15814, 2014.

N. Kikuchi, H. Hosono, H. Kawazoe, O. Tanegashima, I. Ota, and Y. Kimura, “Carrier generation in wide-gap conductor, zinc antimonate,” Journal of the American Ceramic Society, vol. 88, no. 10, pp. 2793–2797, 2005.

C. R. Michel, N. L. López Contreras, M. A. López-Alvarez, and A. H. Martínez-Preciado, “Gas selectivity of nanostructured ZnSb₂O₆ synthesized by a colloidal method,” Sensors and Actuators B: Chemical, vol. 171-172, pp. 686–690, 2012.

J. Tamaki, Y. Yamada, Y. Yamamoto, M. Matsuoka, and I. Ota, “Sensing properties to dilute hydrogen sulfide of ZnSb₂O₆ thick-film prepared by dip-coating method,” Sensors and Actuators B: Chemical, vol. 66, no. 1, pp. 70–73, 2000.

E. Husson, Y. Repelin, and H. Brusset, “Comparaison des champs de force des niobates, tantalates et antimoniates de structure columbite et trirutile,” Journal of Solid State Chemistry, vol. 33, no. 3, pp. 375–384, 1980.

E. Filipek and G. Dąbrowska, “Unknown thermal properties of ZnSb₂O₆ and Zn₇Sb₂O₁₂ compounds: reactivity of α-Sb₂O₄ with ZnO on heating in air,” Journal of Thermal Analysis and Calorimetry, vol. 94, no. 1, pp. 195–201, 2008.

D. Larcher, A. S. Prakash, L. Laffont et al., “Reactivity of antimony oxides and MSb₂O₆ (M = Cu, Ni, Co), trirutile-type phases with metallic lithium,” Journal of the Electrochemical Society, vol. 153, no. 9, pp. A1778–A1787, 2006.

G. Carbajal-Franco, A. Tiburcio-Silver, J. M. Domínguez, and A. Sánchez-Juárez, “Thin film tin oxide-based propane gas sensors,” Thin Solid Films, vol. 373, no. 1-2, pp. 141–144, 2000.

L. Gildo-Ortiz, H. Guillén-Bonilla, J. Santoyo-Salazar et al., “Low-temperature synthesis and gas sensitivity of perovskite-type LaCoO₃ nanoparticles,” Journal of Nanomaterials, vol. 2014, Article ID 164380, 8 pages, 2014.

H. Guillén-Bonilla, L. Gildo-Ortiz, M. L. Olvera-Amador et al., “Sensitivity of mesoporous CoSb₂O₆ nanoparticles to gaseous CO and C₃H₈ at low temperatures,” Journal of Nanomaterials, vol. 2015, Article ID 308465, 9 pages, 2015.

M. L. Arefin, F. Raether, D. Dolejš, and A. Klimera, “Phase formation during liquid phase sintering of ZnO ceramics,” Ceramics International, vol. 35, no. 8, pp. 3313–3320, 2009.

E.-O. Giere, A. Brahimi, H. J. Deiseroth, and D. Reinen, “The geometry and electronic structure of the Cu²⁺ polyhedra in trirutile-type compounds Zn(Mg)1−xCuxSb₂O₆ and the dimorphism of CuSb₂O₆: a solid state and EPR study,” Journal of Solid State Chemistry, vol. 131, no. 2, pp. 263–274, 1997.

H. Mizoguchi and P. M. Woodward, “Electronic structure studies of main group oxides possessing edge-sharing octahedra: implications for the design of transparent conducting oxides,” Chemistry of Materials, vol. 16, no. 25, pp. 5233–5248, 2004.

J. Singh, N. Bhardwaj, and S. Uma, “Single step hydrothermal based synthesis of M(II)Sb₂O₆ ( and Zn) type antimonates and their photocatalytic properties,” Bulletin of Materials Science, vol. 36, no. 2, pp. 287–291, 2013.

S. Wu, G. Li, Y. Zhang, and W. Zhang, “Surface photoelectric and visible light driven photocatalytic properties of zinc antimonate-based photocatalysts,” Materials Research Bulletin, vol. 48, no. 3, pp. 1117–1121, 2013.

B. L. Zhu, C. S. Xie, A. H. Wang, D. W. Zeng, M. L. Hu, and W. Y. Wang, “Electrical conductivity and gas sensitivity of Zn–Sb–O thick films,” Materials Research Bulletin, vol. 39, no. 3, pp. 409–415, 2004.

H. Haeuseler, “Infrared and Raman spectra and normal coordinate calculations on trirutile-type compounds,” Spectrochimica Acta Part A: Molecular Spectroscopy, vol. 37, no. 7, pp. 487–495, 1981.

E. Husson, Y. Repelin, H. Brusset, and A. Cerez, “Spectres de vibration et calcul du champ de force des antimoniates et des tantalates de structure trirutile,” Spectrochimica Acta Part A, vol. 35, no. 10, pp. 1177–1187, 1979 (French).

H. Guillén-Bonilla, J. Reyes-Gomez, A. Guillén-Bonilla et al., “Synthesis and characterization of MgSb₂O₆ trirutile-type in low presence concentrations of ethylenediamine,” Journal of Chemistry and Chemical Engineering, vol. 7, pp. 395–401, 2013.

Z.-X. Deng, C. Wang, X.-M. Sun, and Y.-D. Li, “Structure-directing coordination template effect of ethylenediamine in formations of ZnS and ZnSe nanocrystallites via solvothermal route,” Inorganic Chemistry, vol. 41, no. 4, pp. 869–873, 2002.

X. Wang and Y. Li, “Solution-based synthetic strategies for 1-D nanostructures,” Inorganic Chemistry, vol. 45, no. 19, pp. 7522–7534, 2006.

C. R. Michel, A. H. Martínez, F. Huerta-Villalpando, and J. P. Morán-Lázaro, “Carbon dioxide gas sensing behavior of nanostructured GdCoO₃ prepared by a solution-polymerization method,” Journal of Alloys and Compounds, vol. 484, no. 1-2, pp. 605–611, 2009.

N. J. Dayan, S. R. Sainkar, R. N. Karekar, and R. C. Aiyer, “Formulation and characterization of ZnO:Sb thick-film gas sensors,” Thin Solid Films, vol. 325, no. 1-2, pp. 254–258, 1998.

C.-C. Hsiao and L.-S. Luo, “A rapid process for fabricating gas sensors,” Sensors, vol. 14, no. 7, pp. 12219–12232, 2014.

S. C. Chang, “Oxygen chemisorption on tin oxide: correlation between electrical conductivity and EPR measurements,” Journal of Vacuum Science and Technology, vol. 17, no. 1, pp. 366–369, 1979.

H. Gómez-Pozos, J. L. González-Vidal, G. A. Torres, M. de la Luz Olvera, and L. Castañeda, “Physical characterization and effect of effective surface area on the sensing properties of tin dioxide thin solid films in a propane atmosphere,” Sensors, vol. 14, no. 1, pp. 403–415, 2013.

H. Gómez-Pozos, J. L. González-Vidal, G. A. Torres et al., “Chromium and ruthenium-doped zinc oxide thin films for propane sensing applications,” Sensors, vol. 13, no. 3, pp. 3432–3444, 2013.