Evaluation of structural and dielectric properties of Mn2+-substituted Zn-spinel ferrite nanoparticles for gas sensor applications

Abstract

Polycrystalline MnxZn1–xFe2O4 (x = 0.5, 0.6, 0.7) were prepared by sol-gel auto-combustion and co-precipitation techniques. The microstructural, dielectric and gas sensing properties of obtained ferrite powders were investigated. The FE-SEM pictures revealed the polycrystalline nature of synthesized ferrite samples. The usual dielectric dispersion of spinel ferrites was observed in the ferrite samples. The ferrite sample Mn0.5Zn0.5Fe2O4 prepared by the two methods possessed high dielectric constant at low frequencies. The surface charge polarization is showing predominant influence on the variation of dielectric constant with the composition. The hopping mechanism in differently prepared ferrite systems is interesting and is aroused from the different metal ions located at B–site in the spinel structure. The optimum temperature (OT) of the samples prepared by sol-gel auto-combustion method is 300 °C and co-precipitation technique is 250 °C. The sensor response is exceptionally high for Mn0.7Zn0.3Fe2O4. It is 1.74 and 1.88 in case of sol-gel auto combustion method and co-precipitation method. The ferrite sample Mn0.7Zn0.3Fe2O4 prepared by co-precipitation method is more suitable for the fabrication of gas sensor.