Gas sensing characteristics of magnesium ferrite and its doped variants

Abstract

Spinel structured magnesium ferrite and its nickel, zinc, and copper doped variants were synthesized by the glyoxylate precursor method. The lattice constant and distribution of cations in the tetrahedral ‘A' and octahedral ‘B' sites were obtained by X-ray diffraction (XRD) analysis. Transfer of more Fe3+ into octahedral sites was found due to doping of magnesium ferrite with nickel, zinc, and copper ions. The cation distribution formula agrees with the distribution of Fe3+in A and B sites obtained from the XPS. The photoelectron peak at ≈529.5 eV corresponds to the lattice oxygen, and the adjacent peak at 530.5 eV characterizes the adsorbed oxygen. Evidence of the interplay between electrical conductivity, Fe3+ abundance in the ‘B' site and the lattice oxygen vacancy in the samples was detected. The performance of ferrite as a sensor was investigated using carbon monoxide and methane as analyte gas. We were able to achieve an excellent gas response of 91%with response time (τResp)=133S, against 72 ppm of CO at 300°C, which is far superior to the reported similar studies. The observed response against 32 ppm of methane gas is 56% at 350°C, against the declared values of 45−75% achieved by a higher concentration level (500−2000 ppm) and operating temperature (350−380°C).