Highly sinter-active (Mg–Cu)–Zn ferrite nanoparticles prepared by flame spray synthesis Original Research Article

Nanoscale ZnFe2O4, Mg0.5Zn0.5Fe2O4 and Mg0.2Cu0.2Zn0.62Fe1.98O3.99 powders were prepared for the first time by flame spray synthesis (FSS). Solutions of metal β-diketonates in organic solvents were used as precursor. Crystalline particles of spinel structure with 6–13 nm primary particle size resulted from the flame process. Particle and crystallite size depended on the flow rate of the atomizing gas, the precursor and its molarity. Compacts prepared from Mg–Cu–Zn ferrite nanoparticles revealed an extremely high sinter-activity. A sintered density of 5.05 g cm−3 was achieved after firing for 2 h at 900 °C without any sintering additives, while a maximum density of 4.91 g cm−3 was obtained with particles from the conventional ceramic route. The permeability of the sintered Mg–Cu–Zn ferrite nanopowder compacts reached μ = 600 at 1 MHz and the saturation magnetisation was 80 emu g−1. The outstanding sintering activity of the flame-made ferrite powders is attributed to their small primary particle size.