Enhanced humidity sensing and magnetic properties of bismuth doped copper ferrites for humidity sensor applications

Abstract

In present investigation, the CuFe(2-x)BixO4 (where, x = 0.00, 0.01, 0.02, 0.03) nanoparticles synthesized by solution combustion technique using mixture of fuels as glucose and carbamide. The refined XRD (X-ray diffraction) patterns of the samples confirms the spinel cubic structure having space group Fd3m. The average crystallite size was found to be in nanometer. The lattice parameter, volume, strain and hopping lengths were estimated. TEM (Transmission Electron Microscopy) micrographs confirm the particles are agglomeration. SAED (Selected Area Electron Diffraction) pattern reveals the polycrystalline nature of the material. The magnetic nature of spinel ferrite can be explained by Neel’s two sub-lattice model. In the present work, the observed decrease in magnetization can be ascribed to occupancy and migration of cations at/from B sites by the substitution of Bi3+ ions. The magnetic parameters such as saturation magnetization, remanent magnetization (Mr), coercivity field (Hc), remanence (S), uniaxial anisotropy (Ku) and cubic anisotropy (Kc) were estimated. The resistance and humidity sensing responses increases with increase of the Bi3+ concentration. The hysteresis curves reveal the desorption process is somewhat slower than the adsorption process. The sensing response time 73 s was recorded when sample was moved from 11% RH to 97% RH and the recovery time 36 s was recorded when sample was moved from 97% RH to 11% RH. The humidity sample shows exceptionally stable response at relative humidity 99% RH and 33% RH.