Absence of distinctively high grain-boundary impedance in polycrystalline cubic bismuth oxide

Abstract

In this work, we studied a fluorite structure oxides: Yttria stabilized zirconia, (YSZ); Gd doped CeO2 (GDC); erbia stabilized Bi2O3 (ESB); Zr doped erbia stabilized Bi2O3 (ZESB); Ca doped erbia stabilized Bi2O3 (CESB) in the temperature range of 250 to 600° using electrochemical impedance spectroscopy (EIS). As is well known, grain boundary blocking effect was observed in YSZ and GDC. However, there is no grain boundary effect on ESB, ZESB, and CESB. The Nyquist plots of these materials exhibit a single arc at low temperature. This means that there is no space charge effect on δ-Bi2O3. In addition, impedance data were analyzed by using the brick layer model. We indirectly demonstrate that grain boundary ionic conductivity is similar to or even higher than bulk ionic conductivity on cubic bismuth oxide.