Electrical, thermoelectric, and structural properties of La(MxFe1-x)O-3 (M = Mn, Ni, Cu

Electrical, thermoelectric, and structural properties were studied in transition metal ion-substituted LaFeO3: La(MnxFe1-x)O-3, La(NixFe1-x)O-3, and La(CuxFe1-x)O-3. Structural analysis showed that a continuous series of solid solutions with no intermediate phases are forming over a wide range (0 < x < 1) with substitutions of Mn and Ni, whereas the maximum Cu content is 30% from this study. The Ni-substituted LaFeO3 specimens have substantially higher conductivity than those substituted with either Mn or Cu, measured in air from 100 to 1000 C. The Seebeck coefficient of La(MnxFe1-x)O-3 and La(CuxFe1-x)O-3 has a strong temperature dependence, indicating a thermally activated carrier formation. The activation energy for carrier formation in La(CuxFe1-x)O-3 is greater than that in La(MnxFe1-x)O-3. Thermoelectric and electrical properties evidence conduction through polaron hopping in both Mn- and Cu-substituted LaFeO3, whereas the Ni-substituted LaFeO3 shows metallic conductivity. (c) 2006 The Electrochemical Society.