The constitution of CuFe5O8

Abstract

The physical properties of the system CuFe2O4-Fe 3O4 point to the existence of the compound CuFe 5O8. The activation energies Ea of quenched specimens exhibit an anomaly at the composition CuFe5O8. The log of the resistivities plotted as a function of composition changes slope, the Curie temperatures Tc display a minimum, and the lattice constants A0 show a maximum at or near this composition. As the iron concentration increases, the Seebeck coefficients θ change from positive to negative at the composition Cu0.55(CuFe)0.225Fe 2O4. This is interpreted as being due to the introduction of some ferrous iron at this composition. The equilibrium Cu +1+Fe+3↔Cu+2+Fe+2 lies to the left at least up to this composition. Since the changes in ρ, Ea, A0, and Tc occur at or near the composition CuFe 5O8, it is concluded that only a little ferrous iron exists even in the region of n-type conductivity, and that the copper within parentheses is predominantly monovalent in the series Cu1-2x+2(Cu+1Fe+3)xFe2O 4. © 1965 The American Institute of Physics.