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Sensors & Transducers Journal, Vol. 134, Issue 11, November 2011, pp. 107-119Sensors & TransducersISSN 1726-5479© 2011 by IFSAhttp://www.sensorsportal.comNanostructured Spinel ZnFe 2 O 4 for the Detectionof Chlorine Gas1S. V. Bangale, 2 D. R. Patil and 1 S. R. Bamane1Metal Oxide Research, Laboratory, Department of Chemistry, Dr. Patangrao KadamMahavidyalaya, Sangli 416416 (M.S.) India2Bulk and Nano Materials Research Lab, Dept. of Physics, Rani Laxmibai CollegeParola, Dist – Jalgaon, 425111Tel.: 0233-2535993, fax: No.0233-2535993E-mail: bangale_sv@rediffmail.co, sambhajibamane@yahoo.comReceived: 1 July 2011 /Accepted: 21 November 2011 /Published: 29 November 2011Abstract: Semiconductive nanometer-size material ZnFe 2 O 4 was synthesized by a solutioncombustion reaction of inorganic reagents of Zn(NO 3 ) 3 . 6H 2 O, Fe(NO 3 ) 3 .9H 2 O and Urea as a fuel. Theprocess was a convenient, environment friendly, inexpensive and efficient preparation method for theZnFe 2 O 4 nanomaterial. Effects of the calcining temperature on the phase constituents characterized byTG-DTA, X-ray diffraction (XRD) was used to confirm the material structure, The as-preparedsamples were further characterized by scanning electron microscopy (SEM) equipped with energydispersiveX-ray spectroscopy (EDX), transmission electron microscopy (TEM). To depict thecrystallite microstructure. Conductance responses of the nanocrystalline ZnFe 2 O 4 thick film weremeasured by exposing the film to reducing gases like Acetone, Ethanol, Ammonia (NH 3 ), Hydrogen(H 2 ), Hydrogen sulphide (H 2 S), Chlorine (Cl 2 ) and Liquefied petroleum gas (LPG). It was found thatthe sensors exhibited various sensing responses to these gases at different operating temperature.Furthermore, the sensor exhibited a fast response and a good recovery. The results demonstrated thatZnFe 2 O 4 can be used as a new type of gas-sensing material which has a high sensitivity and goodselectivity to Chlorine (CL 2 ). Copyright © 2011 IFSA.Keyword: Solution combustion reaction, Synthesis, ZnFe 2 O 4 nanoparticles, Gas sensor.1. IntroductionThe need for a novel gas sensor material capable of providing reliable operation in harsh environmentsis now greater than ever. Such sensors find a range of applications, including the monitoring of traffic107
Sensors & Transducers Journal, Vol. 134, Issue 11, November 2011, pp. 107-119pollutants or food quality in specially designed electronic noses [1- 2]. Semiconductor metal oxidesensors are alternatives for non expensive and robust detection system. Spinel-type oxidesemiconductors with formula MFe 2 O 4 have been reported to be sensitive materials to both oxidizingand reducing gases [3]. Liu et al [4] reported the high sensitivity of CdFe 2 O 4 to ethanol vapour; Reddyet al [5] investigated NiFe 2 O 4 as sensor to detect Cl 2 in air. A few Cl 2 gas sensors have already beendeveloped, Transparent conducting oxide (TCO) thin film sensors operate at higher temperature(~300 0 C). However it is inconvenient to operate. It is, therefore, essential to develop a sensor, whichcould detect CL 2 gas at Room temperature. Zirconia tubes, MgO-In 2 O 3 , Zn 2 O 5 -MgIn 2 O 4 (TCO),ZnO-CaO etc., are materials utilized in Cl 2 sensing applications. [6-10]. Chen et al [11] revealed thatMgFe 2 O 4 and CdFe 2 O 4 are sensitive and selective to LPG and C 2 H 2 . Other earlier report about theapplication study of zinc ferrite as a gas sensing material include ZnFe 2 O 4 particles to H 2 S [12], adirectly deposited film to Co [13], ultrafine powder to Cl 2 [14] CdO-doped ZnFe 2 O 4 to ethanol [15], aZnO/ZnFe 2 O 4 thick film to propanol [16], ZnFe 2 O 4 tubes synthesis and application to gas sensors [17].Our latest work about MCo 2 O 4 (M = Ni, Cu, Zn) nanotubes, which possess combined characteristics ofhallow-inside and 1D structure, has displayed excellent selectivity and high sensitivity [18]. In theseregards, zinc ferrite tubes, which not only hold the above mentioned 1D tubular structure but also haveadvantages of low cost and environmental friendliness, are expected to be a good candidate as sensormaterials.Herein, we prepared ZnFe 2 O 4 nanopowder by this simple solution combustion reaction. One of ouraims is to develop a general synthesis method and explore the gas sensing properties of the ZnFe 2 O 4nanopowder obtained. We found that the process is a convenient, environment friendly, inexpensiveand efficient for preparation of ZnFe 2 O 4 nanomaterial with the grain size of about 15-35 nm.Furthermore, the ZnFe 2 O 4 obtained possesses excellent gas-sensing responses to reducing gas. In thepresent paper we report the development of thick film zinc iron oxide Cl 2 sensors.2. Experimental2.1. Sample Preparation and CharacterizationIn this study polycrystalline ZnFe 2 O 4 powder was prepared using urea as fuel. By combustion Rout.The materials used as precursors were Zinc nitrate hexahydrate Zn (NO 3 ) 2 6H 2 O, Fe (NO 3 ) 2 6H 2 O Ironnitrate hexahydrate (all these were procured from A. I. Grade of Qualligen) and (3) urea (Nuclearband). Urea possesses a high heat of combustion. It is an organic fuel and provides a platform forredox reactions during the course of combustion. Initially the Zinc nitrates, Iron nitrates and urea aretaken in the 1:1 :4 stoichiometric amount and dissolved in a 250 ml beaker then slowly string by usingglass rod then clear solution was obtained. Solution formed was evaporated on hot plate in temperaturerange 70 0 C to 80 0 C gives thick gel. The gel was kept on a hot plate for auto combustion and heated inthe temperature range 170 0 C to 180 0 C. The nanocrystalline ZnFe 2 O 4 powder was formed within40-50 minute. And then sintered at about 300, 500, 800 and 1000 0 C for about 4 hours then we getbrown colour shining powder of nanocrystalline ZnFe 2 O 4.Zinc iron oxide powder was ground in an agate pastel-moter to ensure sufficiently fine particle size.The fine powder was calcined at 800 0 C for 24 h in air and re-ground. The thixotropic paste [19-20]was formulated by mixing the resulting ZnFe 2 O 4 fine powder with a soluction of ethyl cellulose (atemporary binder) in a mixture of organic solvents such as butyl carbitol acetate and turpineol. Theratio of inorganic and organic path was kept as 75:25 in formulating the paste. The paste was then usedto prepare thick films. The thixotropic paste was screen printed on a glass substrate in desired patterns.The films prepared were fired at 500 0 C for 24 h.108
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