Structural, dielectric and magnetic properties of particulate composites of relaxor (BaTi 0.85 Sn 0.15 O 3 ) and ferrite (NiFe 2 O 4 ) synthesized by gel-combustion method

Particulate composites of (1-x) BaTi0.85Sn0.15O3 – x NiFe2O4 (with x = 5, 10,15 and 20 wt%) were synthesized using the solid-state reaction method by sintering at 1350 °C for 4 h. Formation of the diphase composites was confirmed by X-ray diffraction (XRD) and Fourier Transform Infra-red (FTIR) techniques. Temperature (RT-200 °C) and frequency (20 Hz- 1 MHz) dependent of AC conductivity, dielectric constant and dissipation have been studied. The dielectric constant exhibits strong frequency dispersion in the range 20 Hz-1 kHz which is attributed to Maxwell-Wagner interfacial polarization occurring at grain-grain-boundaries interface/interface of grains of BTS-NF. The M-H curve of all the composites exhibited a hysteresis loops typical charcateistic of a ferromagnetic material. The ferromagnetic ordering in the composites on account of NiFe2O4 as a constituent is explained using bound magnetic polarons (BMPs) model. The experimental magnetic data have been fitted to BMP model. Value of Ms is smaller, whereas of Hc and Mr are higher of the composites compared to value for NiFe2O4. The temperature at which divergence in the M vs. T plot in ZFC and FC starts is higher for the composites than for NiFe2O4.