Ethanol-sensing characteristics of cadmium ferrite prepared by chemical coprecipitation

Shanghai University, Shanghai, Shanghai Shi, China
Materials Chemistry and Physics (Impact Factor: 2.26). 11/1999; 61(3):192-198. DOI: 10.1016/S0254-0584(99)00133-9

ABSTRACT The microstructure, electrical property and gas-sensing characteristics of complex compounds in the CdO–Fe2O3 system have been investigated. Raw powder with Cd/Fe = 1 : 2 was prepared by chemical coprecipitation method. The results from thermal gravimetric-differential thermal analysis and X-ray diffraction measurement indicate that decomposition of CdCO3 takes place from 350 to 500°C, and the solid reaction in CdO–Fe2O3 system starts at 570°C; the completion of this reaction is up to 800°C. Single phase of CdFe2O4 is composed of spheroidic grains with narrow size distribution between 50 and 150 nm. Sample calcined at 650°C consists of smaller grains with different shape and sizes due to the presence of three phases, i.e., CdFe2O4, CdO and α-Fe2O3. The sensors based on Cd–Fe complex oxides show a high sensitivity and selectivity to C2H5OH gas over CO, H2 and i-C4H10. The sensor made of 650°C sample operates at 380°C, and its sensitivity to 200 ppm C2H5OH gas is up to 90, but its sensitivity to 1000 ppm H2, CO or i-C4H10 are only 7.5, 4 and 5, respectively.

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    • "Desorption leads to an increase in the resistance of p-type nickel ferrite due to the reduction of Ni 3+ to Ni 2+ . With increasing temperature, chemisorbed water desorbs and promotes oxygen adsorption [31] [32]. Overall, a chemisorbed layer of OH groups gives rise to an additional Ni 3+ photoelectron peak and an increased height of the shoulder in O 1s XPS spectra . "
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    ABSTRACT: Pure and cobalt–ion-containing nickel ferrite samples Ni1–xCoxFe2O4 (x = 0, x = 0.01, x = 0.05 and x = 0.1) were prepared by using the sol–gel auto-combustion method. To form the desired structure after the auto-combustion process, the samples were annealed in air at 800 °C for 1 h, followed by slow cooling in air (2.5 °C/min) or rapid cooling by quenching in water. The influences of cobalt ion addition and the cooling rate on the electronic structure, morphology and electrical properties of Ni–Co ferrite were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The gas-sensing properties of pure and cobalt–ion-containing nickel ferrites were studied by using acetone as a test gas. The gas-response of nickel ferrite samples was strongly influenced by the cooling rate and cobalt addition. The effect was attributed to a change in the Ni3+ concentration and a restriction of the transduction of the chemical signal into an output electrical signal. It was demonstrated that the gas response of Ni1–xCoxFe2O4 tends to increase with decreasing cobalt ion content and with decreasing concentration of the point defects such as cation vacancies and Ni3+ ions.
    Sensors and Actuators B Chemical 03/2014; 192:173–180. DOI:10.1016/j.snb.2013.10.077 · 4.10 Impact Factor
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    • "Nowadays , semiconductor metal oxide sensors are extensively studied for their gas response property. Among these materials, the spinel type oxide semiconductors with formula AB 2 O 4 like NiFe 2 O 4 , CdFe 2 O 4 and ZnFe 2 O 4 have been reported to be sensitive materials to both reducing and oxidizing gases [1] [2] [3]. CuFe 2 O 4 is one of the most important ferrites and has a cubic close-packed arrangement of oxygen ions with Cu 2 þ and Fe 3 þ ions at two different crystallographic sites [4]. "
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    ABSTRACT: Undoped and cerium (Ce) doped nanocrystalline copper ferrite (CuFe2O4) materials were synthesized via the molten-salt (M-S) method. Effects of Ce doping on the structural, morphological and gas sensing properties of the CuFe2O4 ferrite have been investigated. X-ray diffraction (XRD) analysis revealed the formation of spinel CuFe2O4. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations showed that the synthesized ferrite is made up of very fine spherical nanoparticles. Moreover, the gas sensing properties of sintered samples were studied towards different reducing gases such as liquefied petroleum gas (LPG), acetone, ethanol and ammonia. The sample with 4% cerium doped CuFe2O4 (Ce4) showed the maximum gas sensitivity (86%) towards LPG with fast response time of 5 s and good recovery time of 68 s.
    Ceramics International 07/2013; 39(5). DOI:10.1016/j.ceramint.2013.01.010 · 2.61 Impact Factor
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    • "ECENTLY, the spinel ferrites (AB O ) have attracted much interest in gas sensors because of their stability in thermal and chemical atmospheres, fast response and recovery time, low cost and simple electronic structure. For example, ZnFe O , MnFe O , NiFe O , and CoFe O have shown good sensitivity for variety of gases [1]–[4]. Among them, cobalt ferrite (CoFe O ) is especially interesting owing to its magnetic properties such as strong anisotropy, high coercive force, moderate saturation magnetization, chemical stability, and mechanical hardness [5], [6]. "
    IEEE Sensors Journal 05/2012; · 1.76 Impact Factor
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