Preparation and gas sensing properties of ZnM2O4 (M = Fe, Co, Cr)

Ultrafine ZnM2O4 (M = Fe, Co, Cr) powders have been successfully fabricated by using a novel polyoxyethylene lauryl ether + n-hexanol/n-heptance/water (zinc nitrate + ferrum nitrate or cobalt nitrate or chromium nitrate) W/O microemulsion method. The composition and the structure of the powers have been investigated by means of XRD and TEM. The results show the as-received ZnM2O4 have spinel-type structure and the every size of the spherical particles are below 60 nm with good dispersity. The influence of temperature on the sensitivities, selectivities, and the response and recovery characteristics are tested. The results of gas sensing measurement show the ZnFe2O4 sensors have a high sensitivity, excellent selectivity and quick response behavior to Cl-2 gas compared with ZnCo2O4 and ZnCr2O4 sensors. The response of ZnFe2O4 to Cl-2 gas shows the resistance increase that indicates an n-type semiconductor behavior while ZnCo2O4 and ZnCr2O4 have p-type semiconductor characteristic. (C) 2003 Elsevier B.V. All rights reserved.