Lattice Parameters of the FeFe(2—x)CrxO4 Spinel System

Abstract

Spinels of the FeFe (2−x) Cr x O 4 ,0⩽x⩽2 , system have been made by reduction of the corresponding sesquioxide solid solution at 1180°C, 1100°C and 950°C and the lattice parameters determined at room temperature. The solutions of approximately stoichiometric composition have lattice parameters which vary with x in a nonlinear manner from 8.396±0.002A at x=0 to 8.376±0.002A at x=2. The four essentially linear segments comprising the total curve are interpreted as follows: from x=0 to x=0.3 the structure is completely inversed; from x=1.28 to x=2.0 it is completely normal; between these regions reversion from the inversed to the normal form occurs in two successive stages. Oxygen‐rich spinels crystallized at 950°C show the same general variations of parameter but the region of complete inversion extends to approximately x=0.6.