Mixed ionic and electronic conductivity of [(ZrO2)(0.92)(Y2O3)(0.08)](1-y) center dot (MnO1.5)(y)

Abstract

Mn2O3 was added to YSZ (8 mol.% Y2O3 doped-stabilized zirconia) either to form a solid solution or two-phase (Mn2O3 and Mn2O3 doped-YSZ) mixed-conducting oxide. The total electrical conductivity was measured between 600 and 1000 degrees C in air using the 4-probe DC method in a wide composition range to determine the composition-dependent conductivity. The Hebb-Wagner polarization technique and the electromotive force measurement by the galvanic cell were used to determine the partial ionic and the electronic conductivity. The entire composition range was divided into three different regions depending upon the conduction mechanisms that were distinguished by the activation energy and the transference number. Within the solubility limit (12 mol.% MnO1.5), the total conductivity and the activation energy of YSZ decreased and increased, respectively, with increasing MnO1.5 content. Above the solubility limit, the total conductivity began to increase slowly due to the rapid increase of the partial hole conductivity which in turn was contributed to the presence of Mn-oxide at the grain boundaries. The total conductivity increased rapidly after 30 mol.% due to the interconnected, conductive Mn2O3 particles. Once percolated above 35 mol.% MnO1.5 content, the activation energies of the composites were nearly the same as that of Mn2O3. Hysteresis behavior shown in the conductivity also provided the evidence of percolation by MnO1.5. (C) 2000 Elsevier Science B.V. All rights reserved.