Preparation Of MgFe₂O₄ Ferrite Film By Sintering Of Layered Double Hydroxide Precursor

The material of ferrite film has been well studied and widely used for magnetic micro-devices, pH electrode, sensor, catalyst, etc, because of its magnetic and electric properties, chemical stability and high mechanical intensity. Although the sol-gel/slurry process gives highly homogeneous films and allows easy control of composition and lower sintering temperatures, production costs of the films are still relatively high since organometallic precursors and organic additives are usually required. Development of a simple, economical and environmentally friendly fabrication process for ferrite films is essential if their potential applications are to be realized in practice. In this work, we show that MgFe(â…¡)Fe(â…¢) layered double hydroxides (LDHs) have been employed as a single-source precursor in the fabrication of MgFe₂O₄ films without the use of organic additive. The structure, morphology and magnetic properties of the resulting film have also been investigated. The details are as follows:1. The well dispersed and stable suspension precursors of MgFe(â…¡)Fe(â…¢)-CO₃-LDHs with initial molar ratio Mg²⁺/Fe²⁺/Fe³⁺ of 2/1/1, 4/5/3 and 1/2/1 were synthesized by separate nucleation and aging steps. The resulting slurrries were cast on theα-Al₂O₃ substrates, followed by drying and sintering at 900℃and 1100℃, forming homogeneous and MgFe₂O₄ granular films. The crystallographic structure, microstructure and chemical composition of the samples have been investigated by XRD, SEM, AFM and EDS. It is shown that the MgFe₂O₄ film sintered at 900℃derived from LDHs with initial molar ratio Mg²⁺/Fe²⁺/Fe³⁺ of 4/5/3 is a stoichiometric nano-granular film.2. The magnetic behaviors of MgFe₂O₄ films and the correlation of structure and magnetic properties of the as-prepared films have been investigated by Vibrating Sample Magnetometer (VSM) and Superconducting Quantum Interference Device Magnetometer (SQUID). The results showed that the MgFe₂O₄ film sintered at 900℃derived from LDHs with initial molar ratio Mg²⁺/Fe²⁺/Fe³⁺ of 4/5/3 has high saturation magnetization and nanosized superparamagnetic particles.