The search for electrolyte materials with high oxygen conductivities is a key step toward reducing the operation temperature of fuel cells, which is currently above 700°C. We report a high lateral ionic conductivity, showing up to eight orders of magnitude enhancement near room temperature, in yttria-stabilized zirconia (YSZ)/strontium titanate epitaxial heterostructures. The enhancement of the conductivity is observed, along with a YSZ layer thickness–independent conductance, showing that it is an interface process. We propose that the atomic reconstruction at the interface between highly dissimilar structures (such as fluorite and perovskite) provides both a large number of carriers and a high-mobility plane, yielding colossal values of the ionic conductivity.

We have analyzed the constant loss contribution to the ac conductivity in the frequency range 10 Hz–1 MHz and temperatures down to 8 K, for two Li ionic conductors, one crystalline ( ${\mathrm{Li}}_{0.18}{\mathrm{La}}_{0.61}{\mathrm{TiO}}_3$) and the other glassy ( $61{\mathrm{SiO}}_2̇35{\mathrm{Li}}_2\mathrm{O}̇3{\mathrm{Al}}_2{\mathrm{O}}_3̇{\mathrm{P}}_2{\mathrm{O}}_5$). As temperature is increased a crossover is observed from a nearly constant loss to a fractional power law frequency dependence of the ac conductivity. At any fixed frequency $\omega$, this crossover occurs at a temperature $T$ such that $\omega \approx {\nu }_0\exp \left({-E}_m/k_{B}T\right)$, where ${\nu }_0$ is the attempt frequency and $E_m$ is identified with the barrier for ${\mathrm{Li}}^{+}$ ions to leave their wells.

We investigated the dynamics of a series of room temperature ionic liquids based on the same 1-butyl-3-methyl imidazolium cation and different anions by means of broadband dielectric spectroscopy covering 15 decades in frequency $\left({10}^{-6}\text{–}{10}^9\mathrm{Hz}\right)$, and in the temperature range from $400\mathrm{K}$ down to $35\mathrm{K}$. Ionic conductivity is observed above the glass transition temperature $T_g$, and below, two relaxation processes appear, with the same features as the secondary relaxations typically observed in molecular glasses. The activation energy of the secondary processes of these ionic systems, and their dependence on the anion, are different. The slower process shows the characteristics of an intrinsic Johari-Goldstein relaxation, in particular an activation energy $E_{\beta }=24k_B{T}_g$ is found, as observed in molecular glasses.

The authors investigate the dynamics of a series of room temperature ionic liquids, based on the same 1-butyl-3-methylimidazolium cation with different anions, by means of broadband (10−6–109Hz) dielectric spectroscopy and depolarized light scattering in the temperature range from 400K down to 35K. Typical ionic conductivity is observed above the glass transition temperature Tg. Below Tg the authors detect relaxation processes that exhibit characteristics of secondary relaxations, as typically observed in molecular glasses. At high temperatures, the characteristic times of cation reorientation, deduced from the light scattering data, are approximately equal to the electric modulus relaxation times related to ionic conductivity. In the supercooled regime and close to Tg, the authors observe decoupling of conductivity from structural relaxation. Overall, room temperature ionic liquids exhibit typical glass transition dynamics, apparently unaltered by Coulomb interactions.