CHARACTERISTICS OF K2NIF4-TYPE OXIDES (SR,SM)2FEO(SIMILAR-TO-4)

Sr1+xSm1-xFeO4-y solid solutions with a composition range 0.00 less th an or equal to x less than or equal to 1.00 have been prepared at 1200 degrees C in air under normal atmospheric pressure. All the solutions exhibit the K2NiF4-type structure of tetragonal system. Mohr salt ana lysis shows that the mole ratio of Fe4+ ion to Fe3+ ion or the tau val ue increases with the x value. Nonstoichiometric chemical formulas hav e been formulated from the x, tau, and y values. Electrical conductivi ty was measured in the temperature range of 173-373 K under atmospheri c air pressure. The conductivities of each sample are varied within th e semiconductivity range. The conductivity at constant temperature inc reases steadily with x value and activation energies are varied from 0 .14 to 0.32 eV. The conduction mechanism of the ferrite system may be proposed as a hopping model of conduction electrons between the mixed valence states. The Mossbauer spectrum for the composition of x=0.00 s hows a six line pattern by which the existence of Fe3+ (I.S.=0.32 mm/s ec) can only be identified. The spectra for the compositions of x=0.50 and 1.00 presents broad single line patterns showing a mixed valence state.