La3+-substituted β-ferrite: Investigation of structural, dielectric, FTIR and electrical polarization properties

This research article reports the exploration of structural, dielectric, optical and electrical polarization properties of β-type hexagonal ferrite KLaxFe11-xO17 upon the substitution of rare earth element La3+ with compositions (x = 0, 0.02, 0.06 and 0.1). The samples were synthesized by adopting the sol-gel auto-combustion technique and the sintering temperature was 950 °C. The XRD patterns revealed the single hexagonal phase for all the samples. The lattice parameters a (Å), c (Å), crystallite size (nm), X-ray density (g/cm3) and unit cell volume V (Å) 3 changed with La3+ substitution. The crystallite size was found to be varied in the range from 24 to 27 nm for all samples as calculated from Scherer formula. Fourier transform infrared spectroscopy (FTIR) spectra also confirmed the single phase for the synthesized samples. The dielectric constant exhibited the higher values than the pure sample with substitution. The dielectric constant results were fitted with the Debye function which indicated the participation of more than one ion in the increment of dielectric constant. The real (M′) and imaginary (M″) part of complex modulus graphs delineated the peaks shifting towards high and low frequency region which confirmed the occurrence of relaxation phenomenon in material. The polarization verses electric field loops corroborated the decrease in saturation and remnant polarization with La3+ contents. The P-E loops also showed the lossy behavior and the increment in lossy behavior with substitution pointed out the increase in resistivity of the samples. From aforementioned evidences, it is confirmed that the present synthesized beta ferrites are useful in the fabrication of humidity sensors and to reduce the eddy current losses. © 2020 Elsevier B.V.