Defect Structure and Properties of Sr-Doped La Cr O_(3-delta)

摘要

A defect chemical model for the behavior of acceptor-doped LaCrO_3 as a function of oxygen pressure is proposed.This is considered within the regime that corresponds to oxygen deficit oxygen.The mathematical approach allows us to calculate the oxygen partial pressure dependant properties of La_(1-x)Sr_xCr O_(3-delta)in the range 0.10 < x < 0.30.The results show that the conductivity was independent of pO_2 and was proportional to the dopant concentration at high pO_2.Therefore,under reducing conditions,the conductivity decreased exponentially with decreasing pO_2 and asymptotically approached a pO_2~(1/4) relationship.Stability regimes and compensation mechanisms at various oxygen partial pressures and temperatures are proposed.This model also examines the charge compensation mechanisms that dominate under the different regimes and their implications for transport properties.From equilibrium constants,thermodynamic quantities such as standard enthalpy and entropy change for the defect formation reactions were calculated.