Electrical Conductivity Of La0 Research Articles

Effect of the Synthetic Method on the Structure and Electrical Conductivity of La0.5Ba0.5FeO3 as SOFC Cathode Materials

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Correlation of thermal properties and electrical conductivity of La0.7Sr0.3Cu0.2Fe0.8O3−δ material for solid oxide fuel cells

A copper-doped ferrite with the chemical composition La0.7Sr0.3Cu0.2Fe0.8O3−δ (LaSrCuFe) was prepared using the classical ceramics method starting from the oxides. The linear thermal expansion coefficient in air was measured in the temperature range between 550 and 1,250 K to be between 10 × 10−6 and 15 × 10−6 K−1. The electrical conductivity in air was found to be higher than 100 S cm−1 for temperatures lower than 1,100 K. A change of oxygen stoichiometry was found above 650 K in an atmosphere of 20 vol% oxygen with argon. This change can be correlated with the electrical conductivity.

Thermal expansion and electrical conductivity of La0.7Sr0.3Mn1 − y CryO3

The thermal expansion and electrical conductivity of La0.7Sr0.3Mn1 − yCryO3 (y = 0, 0.1, 0.3, 0.4) solid solutions have been studied at temperatures from 300 to 1270 K and oxygen partial pressures from 10−9 to 2.1 × 104 Pa. The solid solutions crystallize in rhombohedral symmetry (sp. gr. R3c). The lattice parameters of La0.7Sr0.3Mn1 − yCryO3 decrease with increasing chromium content. Doping with chromium reduces the conductivity of lanthanum manganite, without changing the conductivity type. The charge transport in the solid solutions is due to small-polaron hopping. Disproportionation of the 3d transition metals is shown to play a key role in determining the electrical properties of the solid solutions. Partial chromium substitution for manganese reduces the thermal expansion coefficient of the manganite, improving its compatibility with yttria-stabilized zirconia, which is of practical importance.

Metal–semiconductor transition in novel layered oxychalcogenides

Magnetic and electrical properties were characterized for newly synthesized La1–xSrxOCuSe (0<x<0.25) and La1–xBaxOCuTe (0<x<0.3). Magnetic measurement showed paramagnetic behavior, but it did not obey the Curie–Weiss law, and an ordered phase was not observed down to 1.8 K in the Se and Te systems. The electrical properties of La1–xSrxOCuSe indicated a metal–semiconductor transition at approximately x=0.05 and a metallic state of a higher concentration range x. The electrical conductivity of La0.8Sr0.2OCuSe was 209 S cm−1 at room temperature. In La1−xBaxOCuTe, electrical resistivity systematically decreased with increasing x and semiconductive behavior was observed for all x values. Metal–semiconductor transition is probably caused by the degree of orientation and difference of acceptor levels in this system.

Relative content of the Cr4+ ion and electrical conductivity of La0.75Ca0.25Cr0.75Fe0.25O3

Abstract La0.75Ca0.25Cr0.75Fe0.25O3 is synthesized by a wet chemical method and the electric conductivity of the compound in air is measured over a temperature range from 296 to 1083 K. Arrhenius plot for La0.75Ca0.25Cr0.75Fe0.25O3 is composed of two line segments and the discontinuity is at 532 K. The approximate calculation for the temperature dependence of the electrical conductivity of the compound has been performed in consideration of the thermodynamic equilibrium between the Cr3+ and Cr4+ ions in the compound. The electrical conductivity of lanthanum chromite is directly proportional to the relative content of the Cr4+ ion in the compound and the relative content of the Cr4+ ion in La0.75Ca0.25Cr0.75Fe0.25O3 increases with temperature. The activation energy and the electron hopping frequency may have more significant effect on the electric conductivity of the compound. The occurrence of the oxygen deficiency in the doping lanthanum chromite can be explained by the calculated results.

Sintering behavior and electrical property of la0.68ca0.32cr0.97o3

La0.68Ca0.32Cr0.97O3 separator films were prepared under various sintering conditions. Their bending strength, relative density, electrical conductivity and sintering behavior were investigated by a 4-point bending apparatus, X-ray diffraction (XRD), four terminal method, scanning electron microscooy (SEM) and energy dispersive X-ray spectroscopy (EDX). The bending strength of La0.68Ca0.32Cr0.97O3 at room temperature increased with the increase of sintering temperature and time. A relative density of more than 94% was obtained by sintering at 1673 K for 5 hours. Thus the present investigation revealed that the sintering of La0 68Ca0.32Cr0.97O3 at low temperatures was greatly assisted by the formation of Caa(CrO4)b. Caa(CrO4)b, and incongruently melts and reacts with La1-xCaxCrO3-δ, which enhanced mass transport and resulted in rapid grain growth and densification of the films. Also, the electrical conductivity of La0.68Ca0.32Cr0.97O3 at 1273 K was more than 100 S/cm after heating at 1673 K for 7 hrs.

Role of water vapour pressure on the electrical conductivity of La0.9Sr0.1GaO3

Role of water vapour pressure on the electrical conductivity of La0.9Sr0.1GaO3