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In the present scenario, ferrites are widely used for humidity sensor applications. Aiming this, we have prepared Dy3+-doped Mn–Zn ferrites by solution combustion method combining urea and glucose as burning agent. And obtained powder was characterized by several physicochemical techniques. The phase purity was confirmed by using the techniques such as X-ray powder diffraction and infrared spectroscopy. FTIR spectra show 2 prominent absorption bands under 1000 cm−1 which confirms the formation of spinel ferrite. The dielectric studies with change in frequency exhibited remarkable changes with Dy3+ content in samples. All electrical responses were investigated as a function of frequency and Dy3+ content at room temperature. The dielectric constant and loss on the frequency of the alternating applied electric field is consistent with Maxwell–Wagner style interfacial polarization. Further Humidity sensing response were recorded for pellet samples. It is noteworthy that, as the composition of the Dysprosium (Dy3+) increases the resistance is enhanced and is maximum for the Mn0.5Zn0.5Dy0.03Fe2−0.03O4 composite. Hence our results are good enough for sensor applications.

The present study compiles with the physicochemical, magnetic, and photocatalytic evaluation of the mixed spinel Ni–Zn nanoferrites prepared by the auto-combustion sol–gel route. All the samples were characterized by XRD for the recognition of phase-pure cubic spinel structure. Spectral studies that were carried out by FT-IR clearly show two absorptions band revealing the characteristics of ferrite skeleton. The morphology of the prepared nanoparticles was visualized by SEM and TEM microscopy technique. BET analysis showed the enhancement in surface parameters. Hydrodynamic diameter and dispersion studies were evaluated by DLS and Zeta potential measurements. The DC resistivity measured by two-probe technique shows the semiconductor behavior for all the samples. M–H hysteresis loop of all the samples exhibited the superparamagnetic behavior. The energy bandgap values obtained by the UV–Vis spectroscopy technique show the increasing trend from 1.82 to 2.07 eV with increase in Ni2+ content. The photocatalytic activity of Rhodamine B was evaluated under sunlight irradiation. With increasing Ni2+ concentration, the degradation efficiency increased to 98%. Further, the present nanocatalyst shows active reusability and can be easily separable due to its magnetic nature. The obtained results show the enhanced photocatalytic of the Ni–Zn nanoferrites under the visible light in contrast with the available literature reports.

Magnetic nanofluids (commonly known as ferrofluids) have captured the great attention of the researchers due to their various kinds of applications such as heat transfer, hyperthermia treatments, targeted drug delivery etc. The present experimental investigations deal with the thermoacoustic behaviour of the water based nanofluids of nickel ferrites. The magnetic nickel ferrite nanoparticles were produced by the simple and inexpensive chemical co-precipitation route. The prepared nanoparticles were exposed to different characterization tools for structural, morphological, compositional and magnetic properties analysis. X-ray diffraction analysis with Rietveld refinement confirmed the single phasic nature with nanometric crystallite size of the prepared nanoparticles. Scanning electron microscope images revealed the spherical and nanocrystalline morphology of the prepared nanoparticles. The M-H plot recorded at room temperature revealed the superparamagnetic nature of the nanoparticles. Further, the co-precipitated nickel ferrite nanoparticles with different concentrations were utilized for the preparation of the water based magnetic nanofluids. Colloidal stability of the prepared nanofluids was analyzed by UV–Vis spectroscopy technique and it revealed the stability over 11 days without separation in phase. The temperature dependent thermoacoustic properties of the prepared nanofluids were analyzed through Ultrasonic Interferometer. The interaction between particle–particle and particle–fluid are explained on the basis of thermo-acoustic parameters.