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Vol. 101, Issue 2, February 2009, pp.31-41





Electrical Conduction and Humidity Sensing Properties of NiCr2O4-ZnO-CeO2 Composites


L. Regina Mary, 1K. S. Nagaraja

Department of Chemistry, Loyola Institute of Frontier Energy, Loyola College

Chennai-600 035, Tamil Nadu, India

1Tel.: +91-44-28178200, fax: +91-44-28175566

E-mail: dr.ksnagaraja@gmail.com



Received: 31 December 2008   /Accepted: 20 February 2009   /Published: 28 February 2009


Abstract: Nickel chromite spinels NiCr2O4 was prepared by mixing nitrates of Cr(III) and Ni(II) solutions with urea as fuel at 350oC by combustion method. NiCr2O4-ZnO-CeO2 (NiCZCe) composites with mole ratios 1:1:1, 2:1:1, 1:2:1, 1:1:2, 1:0:1, 0:1:1 and 1:1:0 were prepared and their humidity sensitivity measurements were studied. The samples were sintered at 950oC for 6h and were subjected to DC resistance measurements as a function of relative humidity in the range of 5-98%. The NiCr2O4-ZnO-CeO2 112 composite showed a resistance of 9.6x109 Ω at RH 5% and 7.5x106 Ω at RH 98% with a humidity sensitivity factor of 1273. The 2 mol% Li+ doped NiCr2O4-ZnO-CeO2 112 composite showed an enhanced humidity sensitivity factor of 8471 with a resistance of 3.6x109 Ω at RH 5% and 4.2x105 Ω at RH 98%. The response and recovery time of the highest humidity sensing composites were studied. X-ray diffraction, FT-IR spectroscopy, scanning electron microscopic studies, nitrogen adsorption/desorption isotherm at 77 K and thermoelectric power measurements were employed to the composites to study the structural phases, vibrational frequencies, surface morphology, SBET surface area of the composites and to find the semiconducting nature of the highest humidity sensing composite.


Keywords: Ceramics, Composites, X-ray diffraction, Microporous materials, Electrical, Properties


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