Alternating-current impedance measurements showed that some 1at%Al2O3 could cause an increase in the ionic conductivity of Y2O3-stabilized material, due to a decrease in the grain boundary impedance which was observable at low to medium temperatures. Small additions of α-Al2O3 also caused an overall decrease in the high-temperature impedance. It was found that 10wt%Al2O3 could be added without causing any significant decrease in the ionic conducting properties. Further additions of alumina caused a rapid decrease in conductivity, due to the large volume percentage of insulating alumina phases which were present and due to the cracking of pellets during firing. Hydrothermal ageing, in an autoclave at 180C, of material without Al2O3 additions could lead to a decrease of up to 40% in the conductivity at 1000C. The decrease in conductivity could be limited to only 10% by adding more than 5wt%Al2O3.

Effect of Alumina Additions upon the Electrical Properties of 8mol%Yttria-Stabilised Zirconia. A.J.Feighery, J.T.S.Irvine: Solid State Ionics, 1999, 121[1-4], 209-16