Effects of Al substitution on the properties of NiZnCo ferrite nanopowders

Abstract

Al-substituted NiZnCo ferrite nanopowders, Ni0.4Zn0.5Co0.1AlxFe2−xO4 (0 ≤ x ≤ 0.20), were synthesized by sol–gel auto-combustion method. The influence of Al-substituted NiZnCo ferrite nanopowders on the structural and electromagnetic properties have been studied. The results of TG–DTA show that the precursor decomposition and ferrite formation occurs around 220 °C. The XRD data shows that the lattice constant, nanopowder size and X-ray theoretical density decrease with Al concentration increasing. Ms increases with Al concentration increasing when x ≤ 0.10, and then decreases when x > 0.10. At the same time, Hc decreases with Al concentration increasing when x ≤ 0.10, and then increases when x > 0.10. The Neel temperature decreases with Al substitution increasing. The temperature dependence of dc resistivity of the ferrite nanopowders shows the metal–semiconductor transition behavior. And the influence of Al substitution on the temperature dependence of dc resistivity is investigated.