High-Temperature Electrical Conductivity of LaCr1-xCoxO3 Ceramics

LaCr1-xCoxO3 solid-solution ceramics (x = 0.0-0.3) were prepared by pressureless sintering of a submicrometer powder. The powder was synthesized by a modified glycine nitrate process at 800 degrees C. The electrical conductivity of the material sintered at 1600 degrees C was measured by AC four-wire method from room temperature to 1200 degrees C. While undoped (x = 0) LaCrO3 revealed semiconductivity dominated by thermally activated mobility of small polarons over a vast temperature range, substitution of Co for Cr gave rise for a pronounced enhancement of conductivity at temperatures >200 degrees C. XPS analysis showed that the concentration of Cr4+ on the Cr-site and Co2+ at the Co-site increased with Co substitution suggesting a thermally activated redox reaction Cr3+ + Co3+Cr4+ + Co2+ to create additional charge carriers. Thus, Co doping offers a high potential for designing the electrical conductivity making LaCr1-xCoxO3 an interesting resistivity material for high temperature applications.