High stability and ac-conductivity of cubic fluorite-Bi2O3 films synthesized by magnetron sputtering

Abstract

The electrical properties of nanostructured δ-Bi2O3 and doped Bi2O3 thin films are studied using electrochemical impedance spectroscopy. Firstly, it is shown that films presenting the cubic fluorite Bi2O3 phase can be stabilized in a wide temperature range by adding dopants; from room temperature to 300°C for Al, 500°C for Ta and 600°C for W. An enhancement in the total mixed conductivity of about three orders of magnitude is obtained for the Al-doped films and only of two orders of magnitude for the other dopants in the low temperature range (100–250°C). Impedance analyses suggest that the conductivity is predominantly driven by delocalized ion conduction occurring through the abundant grain boundaries of the nanostructured thin films.