Composition‐Size Effects in Nickel–Zinc Ferrite Nanoparticles Prepared by Aqueous Coprecipitation

Nickel–zinc ferrite nanoparticles across the solid solution range, Ni 1− x Zn x Fe 2 O 4 , from nickel ferrite to zinc ferrite were prepared by aqueous precipitation of mixed nitrate solutions at the same pH of 12.3. There is a linear relationship between the nanoparticle diameter and composition, decreasing with increasing zinc concentration across the solid solution. The nanoparticles are highly resistant to coarsening and some of them are faceted, suggesting that they are close to thermodynamic equilibrium. Measurements of the surface charge density of the nanoparticles, based on simultaneous conductimetric and potentiometeric titration, are presented as a function of composition for the zinc‐rich compositions. A trend exists between the surface charge density and the zinc concentration, suggesting that they may be stabilized by charge.