Origin of colossal ionic conductivity in YSZ/STO multilayers

A colossal eight order of magnitude increase in the ionic conductivity of yttria- stabilized zirconia (YSZ) near room temperature was recently reported in YSZ/strontium titanate (STO) epitaxial heterostructures [1]. We present density functional theory results that explain the enhancement in terms of strain- and interface-induced disorder of the YSZ O-sublattice [2]. We further present experimental confirmation of O disorder using a combination of scanning transmission electron microscopy and electron energy loss spectroscopy. The O K-edge fine structure shows blurred-out features indicative of disorder [3]. Atomic-resolution elemental mapping clearly resolves the O sublattice in the STO but is blurred out in the YSZ, indicating disorder. This work is supported by DOE grant DE-FG02-09ER46554 and DOE Materials Sciences and Engineering Div. 1 J. Garcia-Barriocanal et al. Science 321, 676 (2008); 2 T.J. Pennycook et al., Phys. Rev. Lett. 104, 115901 (2010); 3 T.J. Pennycook et al., European Phys. J.