Structural modifications in Co–Zn nanoferrites by Gd substitution triggering to dielectric and gas sensing applications

Abstract

The structural modifications in Co–Zn ferrites due to the substitution of Gd3+ ions and their credible use as low loss dielectrics and H2S gas sensors are reported in the present study. The structural modifications lead to the enhancement in physical properties of the ferrites making it suitable for the applications. The nanocrystals of Co0·7Zn0·3Fe2-xGdxO4 (0 ≤ x ≤ 0.1, Δx = 0.025) were obtained using self-ignited citrate sol-gel route of synthesis. The X-ray diffractograms of the ferrites were refined by Rietveld method using the full-proof pdf software. The refinement asserts the creation of mono phase spinel ferrite crystals. The morphology of ferrite crystals analyzed from scanning electron microscopy (SEM) profiles depict that the ferrites exhibit the porous nature. The transmission electron microscopy (TEM) images confirms the nanocrystalline nature of the ferrites with an average dimension of 25 nm and high resolution TEM (HRTEM) confirms the spinel phase created within the ferrites. The frequency variation of dielectric parameters was analyzed to study the relaxation phenomenon in ferrites. The values of dielectric constant, dielectric loss and loss tangent were reported to decline with frequency and the Gd3+composition (x). The a.c. electrical conductivity increases with frequency and decreases with composition ‘x’. The room temperature gas sensing response of the ferrite for the hazardous H2S gas was much higher than that for LPG, SO2, NO2 and H2 gases. The ferrite sample with x = 0.025 exhibits a better sensor performance for H2S gas with small recovery and response time. The nanocrystalline nature, porosity and morphology of the ferrites bear control over response and other parameters.