In this paper, the effects of Di ethylene glycol (DEG) embedded Zirconium dioxide (ZrO2) microstructure and Liquid Petroleum Gas (LPG) Sensing characteristics of ZrO2 thin films prepared by spray pyrolysis method were investigated. The films are prepared at X wt. % concentrations (X= 1, 2, 3, 4 and 5) of Di ethylene Glycol. Microstructure of ZrO2 thin film was drastically changed by the addition of DEG, indicating that the addition of DEG was effective to prevent the agglomeration of ZrO2 particles. The high material and phase purities are found from the characterization studies in all as-prepared films. The better sensitivity factor (SF) values SF ~102 (at T = 450C) and SF = 100 (at T = 37oC) are obtained at 1 wt. % and 5 wt. % of Di ethylene Glycol respectively. It is observed that the gas sensing characteristics of these films are strongly influenced by the optimum concentration of DEG due to the high surface area of nano-sized ZrO2 particles

Gawande, S. G.

Khollam, Y. B.

More, Pravin Sadashiv

English

In this paper, the effect of Di ethylene glycol (DEG) embedded zirconium dioxide (ZrO2) on microstructure and liquid petroleum gas (LPG) sensing characteristics of ZrO2 thin films prepared by spray pyrolysis method were investigated. The films are prepared at X wt. % concentrations (X = 1, 2, 3, 4 and 5) of DEG. Microstructure of ZrO2 thin film was drastically changed by the addition of DEG, indicating that the addition of DEG was effective to prevent the agglomeration of ZrO2 particles. The high material and phase purities are found from the characterization studies in all as-prepared films. The better sensitivity factor (SF) values SF ~102 (at T = 450C) and SF = 100 (at T = 37oC) are obtained at 1 wt. % and 5 wt. % of DEG respectively. It is observed that the gas sensing characteristics of these films are strongly influenced by the optimum concentration of DEG due to the high surface area of nano-sized ZrO2 particles

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72 Journal of Research Updates in Polymer Science, 2012, 1, 72-74    E-ISSN: 1929-5995/12  © 2012 Lifescience Global Synthesis and Study of Electrical Properties of Di Ethylene Glycol Embedded ZrO2 Films as a Gas Sensor  P.S. More*, Y.B. Khollam and S.G. Gawande Department of Physics, Novel Material Characterization Laboratory, Government Institute of Science, Mumbai 400 032 (MS), India Abstract: In this paper, the effects of Di ethylene glycol (DEG) embedded Zirconium dioxide (ZrO2) microstructure and Liquid Petroleum Gas (LPG) Sensing characteristics of ZrO2 thin films prepared by spray pyrolysis method were investigated. The films are prepared at X wt. % concentrations (X= 1, 2, 3, 4 and 5) of Di ethylene Glycol. Microstructure of ZrO2 thin film was drastically changed by the addition of DEG, indicating that the addition of DEG was effective to prevent the agglomeration of ZrO2 particles. The high material and phase purities are found from the characterization studies in all as-prepared films. The better sensitivity factor (SF) values SF ~102 (at T = 450C) and SF = 100 (at T = 37oC) are obtained at 1 wt. % and 5 wt. % of Di ethylene Glycol respectively. It is observed that the gas sensing characteristics of these films are strongly influenced by the optimum concentration of DEG due to the high surface area of nano-sized ZrO2 particles Keywords: DEG, Spray pyrolysis, LPG, Gas sensor, thin film. INTRODUCTION Now a days, the increase in ecological perception, fitness, and safety are involving the greenhouse, inflammable and poisonous gases. As a result, there is an urge of reliable and contemptible gas sensors [1-12] to control the emission of gases. Polymer embedded Metal oxide semiconductor is the most widely used to detect oxidizing gases and it also prevents from atmospheric wetness. Moreover, there are new approaches to improve the Metal Oxide semiconductor sensors by modifying the surface morphology with the help of polymer [10-13]. In this present work, we have synthesized the DEG embedded ZrO2 film using the spray technique. An organic structure-directing agent is used in this synthesis process. The samples obtained from above mentioned process were heated up-to a particular temperature 100oC. In this study, effect of DEG addition on the microstructure and sensor characteristics of ZrO2 thin film was investigated. 2. EXPERIMENTATION Standard commercially available Zirconium oxy chloride (99.8 % pure, SISCO RESARCH PVT LTD) and pure Di ethylene Glycol (DEG) (S.D. Fine chime Ltd) were used to prepare the thin films. Initially, 1 molar solution of Di ethylene Glycol and Zirconium Oxichloride was prepared. PEG content was varied    *Address corresponding to this author at the Department of Physics, Novel Material Characterization Laboratory, Government Institute of Science, Mumbai 400 032 (MS), India; Tel: +91 09422759961;  E-mail: p_smore@yahoo.co.in from 0 to 5 wt. % of precursor solution. Then the thin films of each of concentration were prepared by spray pyrolysis method on glass slides which is used as substrate. ZrO2 thin films were deposited on glass substrate by spray pyrolysis method, followed by baking at 100 oC in air ambient immediately. Sensing properties were studied for all the films for LPG by recording the change in the voltage across the sample by half bridge method. The sensor characteristic was evaluated by the electrical conductivity of thin films between electrodes in the temperature range of 30-100 oC. The sensitivity factor (SF) of the sensor was defined as (Rg /Ra)*100, where Ra is resistance in air, and Rg resistance in LPG gas at 1000 ppm concentration.  3. RESULTS AND DISCUSSION Sensor study: As already reported, the gas sensitivity was almost linear to the concentration of LPG at 1000 ppm from Room Temperature to 100°C for the ZrO2 based device. The gas sensitivity is defined as the ratio of resistance of sample in gas (|R|gas) surroundings and its resistance in air i.e. (|R|air). The sensor study is optimized for following condition (i) Temperature Selectivity (ii) optimization of weight concentration. 3.1. Temperature Selectivity Figure 1 shows the variation of sensitivity factor with respective optimum operating temperature for different weight concentration of DEG. It can be seen that for 1 wt. % sample, the sensitivity up to 37°C is almost constant and increase rapidly at 45°C and further Synthesis and Study of Electrical Properties of Di Ethylene Glycol Journal of Research Updates in Polymer Science, 2012 Vol. 1, No. 2      73 decrease up to 57°C and then again remains constant. The flat response is obtained for the samples of 2, 3, and 4 wt. % of DEG modified samples at all the temperatures range from 30-100° C.   Figure 1: Variation of SF (sensitivity factor) with temperature for LPG gas (1000 ppm) at (a) 1, (b) 2, (c) 3, (d) 4, and (e) 5, wt.% of DEG for DEG /ZrO2 system. However, it has shown that the sensitivity to 5 wt. % sample (SF~102) increase continuously up to 37°C and decrease further to 100oC, even sensitivity noticeable at low temperature, but the temperature window for 1 wt. % samples is less as compared 5wt% sample are summarized in Table 1. The response and recovery responses were rather quick.  3.2. Optimization of Weight Concentration From Figure 2a it reveals that 1 Wt. % Di ethylene Glycol modified sample gives more sensitivity (SF = 101. 20) at 47oC as compared to 2, 3, 4 wt. % Di ethylene Glycol modified samples. While, 5 Wt. % Di ethylene Glycol modified sample (Figure 2b) gives less sensitivity (SF= 101.18) at 37°C. Further investigation like XRD, SEM and activity of LPG on the sensor study is now in progress. It seems that both adsorption and combustion of the reducing gases occurs on the surface of the sensors. The depletion of the lattice oxygen might be responsible for the sensitivity of the sensor to the gases. The ZrO2 is a lower temperature semiconductor than other oxides and exchanges lattice oxygen with surface and gas-phase oxygen more easily [5, 11]. We speculate that at 35°C, the LPG can easily extract more oxygen from the lattice of the sensor. Thus, in ZrO2 sensor the lattice oxygen is easily replaced from the gas and causes the change in resistance/conductivity of sample.  Yamazoe and Miura [7] reported that the sensitivity was drastically developed by decrease in the crystalline size to a few nano-meters (crystallite size effect). In addition, it was reported that the thin film thickness under a micron-meter and addition that the improvement of sensitivity of ZrO2 thin film was brought by high surface area of nanosized ZrO2 particles and high oxygen defect concentration caused by the combustion of organic chemical modifier reagent (DEG) was effective to enhance the sensitivity of the sensors [12,13]. In our results, the addition of PEG was so effective to decrease the particle size of the SnO2 thin films that sensitivity of the SnO2 thin film could drastically be enhanced.The atmospheric oxygen adsorbs on the surface by extracting an electron from conduction band, in the form of super oxides or peroxides, which are mainly responsible for detection of the test gases. At higher temperature it captures the electrons from conduction bands as  O2 (air) + 4 e- (conduction band)  2O2- (film surface) It would result in decrease in conductivity of the samples. When LPG reacts with the adsorbed oxygen on the surface of the samples it get oxidizes to CO2 and H2O, liberate free electrons in the conduction bands. The reaction that takes place is as  C4H10 (gas) + 13O2- (film surface)  4CO2 (gas) + 5H2O (gas) + 26 e- (conduction band)  This shows the n-type conduction mechanism. Thus generated electron contributes to sudden increase in Table 1: Variation of Weight Concentration with Respective Optimum Operating Temperature °C. additive Weight % Maximum sensitivity Optimum operating Temp. Temperature window in °C 1 101.20 45°C 4 2 97 - NIL 3 10 - NIL 4 99 - NIL 5 101.18 37°C 10 74     Journal of Research Updates in Polymer Science, 2012 Vol. 1, No. 2 More et al. conduction of the samples. As the temperature is increased, the ZrO2 can exchange lattice oxygen with surface and the gas. The dramatic effect of Zirconium on LPG selectivity needs further investigation.  3. CONCLUSION The DEG embedded ZrO2-based materials used in gas sensors have received great attention. The high and selective absorption properties of DEG embedded ZrO2 towards a specific gas greatly enhances the sensing selectivity for the gas. The compound or cluster sensing towards a gas assembled into the cages or channels of DEG embedded ZrO2 results in its high stability, and maximally elevate the sensing property of the materials. The application of composite materials partially composed of a DEG, opens novel ways for choosing gas sensor materials as well. However, much more work remains to be done. Overall, we foresee that DEG embedded ZrO2 will become widely available material for gas sensing in the next few years. REFERENCES [1] Fuller MJ, Warwick ME. The catalytic oxidation of carbon monoxide on tin (iv) oxide. J Catal 1973; 29: 441-50. http://dx.doi.org/10.1016/0021-9517(73)90251-0 [2] Tatsuyama CH. Ichimuraand SH. Iwakuro H. Observation of GaSe–SnO2 heterostructure by XPS and AES. Jpn J Appl Phys 1982; 21: L25-L27.  http://dx.doi.org/10.1143/JJAP.21.L25 [3] Chaudhary VA, Mulla IS, Sainkar SR, Belhekar AA, Vijayamohanan K. Surface ruthenated tin oxide as a novel hydrocarbon sensor. Sensors Actuators A 1988; 65: 197-202. http://dx.doi.org/10.1016/S0924-4247(97)01688-9 [4] Duh JG, Jou JW, Chiou BS. Catalytic and gas sensing characteristics in Pd doped SnO2. J Electrochem Soc 1989; 136: 2740-47. http://dx.doi.org/10.1149/1.2097581 [5] Ippommatsu M, Sasaki H, Yanagida H. Sensing mechanism of SnO2 gas sensors. J Mater Sci 1990; 25: 259-62.  http://dx.doi.org/10.1007/BF00544217 [6] Yamazoe N. New approaches for improving semiconductor gas sensors Sensors Actuators B 1991; 5: 57-19. http://dx.doi.org/10.1016/0925-4005(91)80213-4 [7] Yamazoe N, Miura N. In: Yamauchi S, Ed. Chemical Sensor Technology, Kodansha/Elsevier, New York 1992; vol. 4: pp. 19-42. [8] Ruu AR, Seshdrj K, Rao CNR.  Investigations of V2O5 Based LPG Sensors Talonto 1992; Vol. 39/11: pp. 1543-1547. [9] Orlik DR, Ivanovskaya MI, Kol KD. Characterization of semiconducting tin oxide films sensors prepared by sol–gel method. J Anal Chem 1995; 50: 1073-77. [10] Schweizer B, Berberich M, Zheng JG, Weimar U, Goepel W, Barsan N, et al. The effect of Pt and Pd doping on the response of nanocrystalline SnO2 gas sensors to CO, Sensors Actuators B 1996; 31: 71-75. http://dx.doi.org/10.1016/0925-4005(96)80018-9 [11] Chaudhary VA, Mulla IS, Vijayamohanan K. Synergistic sensitivity effects in surface modified tin oxide using Ru–Pd oxides. J Mater Sci Lett 1997; 16: 1819-21. http://dx.doi.org/10.1023/A:1018568702315 [12] Shimizu Y. Development of high performance semiconductor gas sensors by micro- and macro-structural design. Chem Sensors 2002; 18: 42-54. [13] Shoyama M, Hashimoto N. Effect of poly ethylene glycol addition on the microstructure and sensor characteristics of SnO2 thin films prepared by sol–gel method. Sensors Actuators B 2003; 93: 585-89. http://dx.doi.org/10.1016/S0925-4005(03)00215-6   Received on 16-10-2012 Accepted on 02-12-2012 Published on 31-12-2012  DOI: http://dx.doi.org/10.6000/1929-5995.2012.01.02.2       (a)       (b) Figure 2: Variation of SF with temperature for LPG gas (1000 ppm) at (a) 1, and (b) 5 wt.% of Cu for Di ethylene Glycol/ZrO2 system. 

Synthesis and Study of Electrical Properties of Di Ethylene Glycol Embedded ZrO2 Films as a Gas Sensor

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Synthesis and Study of Electrical Properties of Di Ethylene Glycol Embedded ZrO2 Films as a Gas Sensor

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