Protonic conductivity of nano-structured yttria-stabilized zirconia: dependence on grain size

The conductivity of dense ceramics of nanocrystalline yttria-stabilized zirconia (nano-YSZ), with average grain sizes ranging from 13 nm to 100 nm, was measured in wet and dry air as a function of temperature between 30 °C and 500 °C. Under wet conditions (pH2O = 2.3 × 10−2 atm) the measured conductivity at low temperatures (<150 °C) was found to increase strongly with decreasing grain size, displaying a highly non-linear dependence on grain size. This is interpreted as evidence of the protonic conductivity of grain boundaries increasing with decreasing grain size.