Solid State Ionics, Vol.117, No.3-4, 229-243, 1999
Electronic conductivity of Gd-doped ceria with additional Pr-doping
The electronic conductivity of ceria doped with 20 - x mole% Gd and x mole% Pr according to the composition Ce0.8Gd0.2-xPrxO1.9 (with 0.01 less than or equal to x less than or equal to 0.03) was measured as a function of oxygen activity in the range from a(O2) approximate to 10(2) to a(O2) approximate to 10(-15) (a(O2) = 1 corresponding to a gas with oxygen partial pressure p(O2) = 1.013 bar) for temperatures between 600 degrees C and 750 degrees C and compared with results for Pr-free Ce0.8Gd0.2O1.8. The Hebb-Wagner polarization technique was used with an encapsulated Pt-microcontact in an N-2 atmosphere and a Cu2O/CuO reference electrode. Addition of 1-3 mol% Pr leads to a slightly decreased electron conductivity in the n-type range, but to a large increase in the p-type range. Moreover, the minimum of the electronic conductivity is shifted to lower oxygen activities by doping with Pr (e.g. at 700 degrees C: from an oxygen activity of 5x10(-4) for Ce0.8Gd0.2O1.9 to 5x10(-6) for Ce0.8Gd0.17Pr0.03O1.9). The activity dependence of the electronic conductivity in the n-type and p-type range slightly deviates from the theoretically expected values (sigma(n,p)(proportional to)a(O2)(=1/m) with 4