B. J. Scarfino

Electrical, Thermoelectric, and Structural Properties of La ( M x Fe1 − x ) O3 ( M = Mn , Ni , Cu )

Electrical, thermoelectric, and structural properties were studied in transition metal ion-substituted LaFeO 3 : La(Mn x Fe 1-x )O 3 , La(Ni x Fe 1-x )O 3 , and La(Cu x Fe 1-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 LaFeO 3 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(Mn x Fe 1-x )O 3 and La(Cu x Fe 1-x )O 3 has a strong temperature dependence, indicating a thermally activated carrier formation. The activation energy for carrier formation in La(Cu x Fe 1-x )O 3 is greater than that in La(Mn x Fe 1-x )O 3 . Thermoelectric and electrical properties evidence conduction through polaron hopping in both Mn- and Cu-substituted LaFeO 3 , whereas the Ni-substituted LaFeO 3 shows metallic conductivity.

Structural and magnetic properties of LaMn1−xFexO3 (0<x<1.0)

Electronic, structural, and magnetic properties of Mn-doped lanthanum ferrites were studied by neutron diffraction, superconducting quantum interference device, and impedance spectroscopy. Neutron diffraction refinements were performed with the constraint of full La occupancy, which showed the presence of excess oxygen when x 0.7 are magnetically ordered at room temperature with orthorhombic symmetry (Pbnm). When x<0.3 the structure is rhombohedral and magnetically disordered above 16K. The majority carriers, electron holes, correspond to high oxidation states of Mn. The carrier concentration is determined from the Seebeck coefficients, and is a function of temperature and Fe concentration. The measurements of conductivity and Seebeck coefficients show polaron hopping at elevated temperatures.

Structural and Magnetic Properties of La Mn₁₋ₓFeₓO₃ (0

Electronic, structural, and magnetic properties of Mn-doped lanthanum ferrites were studied by neutron diffraction, superconducting quantum interference device, and impedance spectroscopy. Neutron diffraction refinements were performed with the constraint of full La occupancy, which showed the presence of excess oxygen when x 0.7 are magnetically ordered at room temperature with orthorhombic symmetry (Pbnm). When x<0.3 the structure is rhombohedral and magnetically disordered above 16K. The majority carriers, electron holes, correspond to high oxidation states of Mn. The carrier concentration is determined from the Seebeck coefficients, and is a function of temperature and Fe concentration. The measurements of conductivity and Seebeck coefficients show polaron hopping at elevated temperatures.

Structural and magnetic properties of la Mn1-x Fex O3 (0<x<1.0)

Electronic, structural, and magnetic properties of Mn-doped lanthanum ferrites were studied by neutron diffraction, superconducting quantum interference device, and impedance spectroscopy. Neutron diffraction refinements were performed with the constraint of full La occupancy, which showed the presence of excess oxygen when x 0.7 are magnetically ordered at room temperature with orthorhombic symmetry (Pbnm). When x<0.3 the structure is rhombohedral and magnetically disordered above 16K. The majority carriers, electron holes, correspond to high oxidation states of Mn. The carrier concentration is determined from the Seebeck coefficients, and is a function of temperature and Fe concentration. The measurements of conductivity and Seebeck coefficients show polaron hopping at elevated temperatures.