Structural and physical properties of Ni–Tb–Fe–O system

A series of soft ferrites in the system Ni1 − xTbxFe2O4 (0 ≤ x ≤ 0.2), was prepared by a standard ceramic technique. The influence of terbium content was investigated by means of X-ray diffraction, Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy. The X-ray diffraction analysis reveals that the samples have a cubic spinel (single phase) structure for 0 ≤ x ≤ 0.08; for x > 0.08 a small peak of orthorhombic phase (TbFeO3) appears and becomes more conspicuous with increased terbium substitution. The lattice parameter changes in a non-linear way as a function of terbium content which may be attributed to differences in the ionic radii of the cations involved and the solubility limit of terbium ions. A gradual increase in the bulk density was observed with the increase of terbium concentration, from 5.13 g/cm3 to 5.69 g/cm3. FTIR absorption spectra of the Ni–Tb–Fe–O system were investigated in the wave number range 370–1500 cm− 1. Each spectrum exhibited two main absorption bands, thereby confirming the spinel structure.