Electrical conductivity and high dielectric constant are in principle self-excluding, which makes the terms insulator and dielectric usually synonymous. This is certainly true when the electrical carriers are electrons, but not necessarily in a material where ions are extremely mobile, electronic conduction is negligible and the charge transfer at the interface is immaterial. Here we demonstrate in a perovskite-derived structure containing five-coordinated Ti atoms, a colossal dielectric constant (up to \mbox109) together with very high ionic conduction \mbox10−3\mboxS.cm−1 at room temperature. Coupled investigations of I-V and dielectric constant behavior allow to demonstrate that, due to ion migration and accumulation, this material behaves like a giant dipole, exhibiting colossal electrical polarization (of the order of \mbox0.1C.cm−2). Therefore, it may be considered as a "ferro-ionet" and is extremely promising in terms of applications.
@article{arxiv.1703.01422,
title = {$\mbox{Rb}_{2}\mbox{Ti}_2\mbox{O}_{5-\delta}$: A superionic conductor with colossal dielectric constant},
author = {Rémi Federicci and Stéphane Holé and Aurelian Florin Popa and Luc Brohan and Benoît Baptiste and Alexis S. Borowiak and Silvana Mercone and Brigitte Leridon},
journal= {arXiv preprint arXiv:1703.01422},
year = {2017}
}