Structural features and dielectric behavior of Al substituted Cu0.7Ni0.3Fe2O4 ferrites

Abstract Aluminum doped Cu–Ni based spinel nano-ferrites Cu0.7Ni0.3Fe2-xAlxO4 are synthesized via sol-gel route and characterized by XRD, FTIR, impedance analyzer, EDAX and SEM. Phase analysis reveals a cubic spinel structure having a single phase. SEM images confirms the uniform formation of materials and elemental stoichiometry is confirmed from EDAX spectra. The size of crystals is within the range of 28.38–30.04 nm. The lattice constant decreases from 8.614 to 8.604 A with the increase of Al3+ concentration. The metal-oxygen oscillations at octahedral and tetrahedral sites are confirmed by FTIR. Dielectric constant, tangent loss and quality factor are investigated using impedance analyzer within frequency range 1 MHz–3 GHz. Dielectric constant is significantly affected with Al3+ substitution and attained 16.1 value at 2.3 GHz for Cu0.7Ni0.3Fe1.7Al0.3O4. Furthermore, Cu0.7Ni0.3Fe1.7Al0.3O4 showed maximum dielectric loss of 0.4 at 2.5 GHz. The quality factor is enhanced up to 1500 with substitution of Al3+ at concentration of x ═ 0.3. Outstanding dielectric properties of nano-particles suggest that they are good candidates for high-frequency devices and super-capacitors.