Electrical properties of yttria-stabilised hafnia ceramics

Cubic, yttria-stabilised hafnia, YSH, ceramics of general formula, YHf_1-O_2-: x = 0.15, 0.30 and 0.45 were sintered at 1650-1750 °C and characterised by impedance spectroscopy. All three compositions are primarily oxide ion conductors with a small amount of p-type conductivity that depends on atmospheric conditions and appears to increase with x. The electronic conductivity is attributed to hole location on under-bonded oxide ions and the absorption of oxygen molecules by oxygen vacancies, both of which occur on substitution of Hf⁴⁺ by Y³⁺. Composition x = 0.15 has the highest total conductivity and shows curvature in the Arrhenius plot at high temperatures, similar to that of the most conductive yttria-stabilised zirconia.