FORMATION OF NANOCRYSTALLINE NIFE2O4

Coprecipitates, Ni(OH)(2) + 2Fe(OH)(3), were milled in a planetary mil l, using an agate bowl and balls (99.9% SiO2), and then heated at a ma ximum temperature of 573 or 773 K. The Mossbauer spectra at 298 K of t he ball-milled samples (not healed) showed the superposition of two qu adrupole doublets. After heating at 573 K, the superposition of two do ublets was preserved at 298 K with a slight increase in the quadrupole splitting for the sample ball-milled for 64 h. After heating at 573 K , the ball-milled samples showed at 80 K a central quadrupole doublet and a sextet with very broad lines. All the samples heated to 573 K we re amorphous for according to X-ray diffraction while those heated to 773 K exhibited crystalline NiFe2O4 with broadened diffraction lines. At 298 K, superposition of two sextets in the Mossbauer spectra was ob served for the samples obtained after heating at 773 K, indicating the presence of nickel ferrite as a single phase. The average sizes of Ni Fe2O4 crystallites were in the nanosize range (8-12 nm). The Fourier t ransform infrared spectra of the samples heated at 773 K showed two ve ry strong bands with positions at 601-603 and 408-411 cm(-1), which ca n be ascribed to NiFe2O4.