Vol. 91, Issue 4, April 2008, pp.100-108

Role of Cu²⁺ Concentration on the Microstructure and Gas Sensing Properties of   Ni_1-xCu_xFe₂O₄ (0 ≤ x ≤ 0.8) Ferrite

Elena Rezlescu, Florin Tudorache, Paul Dorin Popa and Nicolae Rezlescu

National Institute of Research and Development for Technical Physics, 700050 Iasi, Romania

reznic@phys-iasi.ro

Received: 19 March 2008   /Accepted: 21 April 2008   /Published: 30 April 2008

Abstract: The microstructure and gas sensor properties of some nanostructured soft ferrites (Ni_1-xCu_xFe₂O₄, x = 0.2, 0.4, 0.6, 0.8) are studied. Using sol-gel self-combustion technology and subsequent heat treatment were prepared ferrite powders, having molecular scale homogeneity and nanosized granulation. The scanning electron microscopy (SEM) was used to investigate morphology and pore structure. The effect of operating temperature and copper content on the fundamental features of a sensor element such as sensitivity and response time towards acetone, ethanol and LPG vapour has been studied. All samples are sensitive to ethanol and acetone and have a poor sensitivity to LPG. For a large copper content (x > 0.4) the electrical response to ethanol is larger than that to acetone, at the same working temperature, of 280^oC. Among the investigated ferrites, Ni_0,2Cu_0,8Fe₂O₄ composition shows the best sensitivity to ethanol (about 70 %) at operating temperature of 280^ºC. The gas sensitivity increases with increasing gas concentration from 25 to 150 ppm, whereas the response time decreases.

Keywords: NiCu ferrite; Microstructure; Sensing properties; Response time; Reducing gas

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