EFFECTS OF DOPING ON THE THERMAL-STABILITY OF SPINDLE-SHAPED GAMMA-FE2O3 PARTICLES

Spindle-shaped alpha-FeOOH particles were synthesized using the chemic al coprecipitation method in Fe(CO3)(x)(OH)(2(-x)) suspensions system by adding metallic ions. The spindle-shaped gamma-Fe2O3 particles were obtained by dehydration of alpha-FeOOH, and subsequent reduction and oxidation. its thermal stability was investigated by differential ther mal analysis (DTA). It was found that the transition temperature of ga mma-Fe2O3 --> alpha-Fe2O3 of samples doped with metallic ions is highe r than that of the pure gamma-Fe2O3 and increasing with increase of th e size of the metallic ions, and gamma-Fe2O3 by doping with two or mor e different metallic ions together has even higher thermal stability. The origin of the improved thermal stability was discussed. Additional ly, the magnetic properties of gamma-Fe2O3 were measured.