STABILITY OF PHASES IN COPPER FERRITE

Phase stabilities in copper ferrite are studied with substitution of T i and Ge tetravalent ions. In Ti-substituted samples (Cu1+xTixFe2-2xO4 ) the parent tetragonal structure is retained up to x=0.15, and for hi gher content of Ti it changes to cubic. In the case of Ge-substituted samples (Cu1+xGexFe2-2xO4), the cubic structure is observed for 0.0<x less than or equal to 0.2, and the tetragonal structure reverts for hi gher contents of Ge. The origin of the distortion lies in square coval ent bond formation of copper ions at the octahedral site. The observed results are explained on the basis of cation distribution and covalen t bond formation of copper and germanium ions.