PHYSICOCHEMICAL AND ELECTROCHEMICAL PROPERTIES OF THE LA0.6SR0.4MN1-X(CO,NI)(X)O-3 ELECTRODE MATERIALS

The structural, thermal, electrical, and electrochemical properties of the electrode materials La0.6Sr0.4Mn1-x (Co, Ni)(x)O-3, where x = 0-0 .05, are studied, It is found that adding transition metals in cubic p erovskites raises the Mn4+ ion concentration from 49 to 57%. The manga nite conductivity rises at room temperature from 250 to 700 S cm(-1) a t x = 0 and x = 0.02 Ni, respectively. At 300-1100 K, all samples have metallic conduction; samples with x = 0.02 have the maximum conductiv ity. The coefficient of linear thermal expansion is virtually independ ent of the doping and varies in the region (13.9-14.6) x 10(-6) K-1. I n the temperature range 300 to 1100 K, changes in the resistance param eter of the interface between the electrode and solid electrolyte. are of a semiconductor nature. The activation energy for conduction varie s from 6.7 to 23.4 kJ mol(-1). The minimum magnitude of the resistance parameter is intrinsic to samples coated with manganite of the compos itions corresponding x = 0.05. Increasing the electrode layer thicknes s from 20 to 100 mg cm(-2) reduces the resistance parameter 2 to 20 ti mes. The surface resistance of samples of compositions studied remains almost invariable at P-O2 = 10(2)-10(5) Pa. Introducing additives of transition metals in La0.6Sr0.4MnO3 reduces the polarization resistanc e of the gas-electrode-solid electrolyte interface. At 773-1073 K and 10(2)-10(5) Pa, the minimum values of the polarization resistance are intrinsic to electrode layers 50 mg cm(-2) thick, containing 0.05 mol Co or Ni.