Mechanochemistry of Spinel-Type Ferrite Powders

Abstract

Mechano-chemical reactions and.structural changes of some spinel-type ferrite powders by grinding have been investigated.It was observed that the mechano-chemical reaction occurred on the MgFe2O4 particle surface during wet grinding and a thin layer containing combined water was formed on the surface. The thickness of the layer was almost constant independently of the grinding duration. The calculated values of OH's/100A2 (the number of OH radical per unit surface area) for wet ground samples were in the range of 62 to 66. The Mg0.86Mn0.43Fe0.71O4 powder was subjected to various wet grinding treatments using the following three types of mill: 1) attritor, 2) ball mill, 3) vibratory mill. The thickness of the layer containing combined water was nearly constant independently of a variety of grinding treatments. The calculated values of OH's/100A2 were in the range of 79 to 92.The powder of ordered Li0.5Fe2.5O4, in the spinel structure of which the Li and Fe ions make 1:3 ordering at the octahedral sites, were wet ground in a ball mill. As a result, the long-range order parameter decreased with increasing the grinding time.In the case of the CuFe2O4 powder, the tetragonal structure was gradually transformed to the cubic one with grinding. The mechanism of this mechanochemical polymorphic transformation can be explained by the destruction of a cooperative Jahn-Teller effect by grinding.