The rare earth dopant (La, Gd, Sm & Y) modulated grain boundary energy barrier suppression in BaZrO3-BaCeO3 solid solution

The charge depletion near the grain boundary region in proton-conducting BaZrO3 electrolyte results in large potential barrier for the proton migration. Alternatively, a barium zirconate-cerate solid solution has been shown to improve the protonic conductivity by lowering the charge depletion along the grain boundary. Here, we report the modulation in grain boundary resistance of barium cerate - zirconate solid solution in the presence of trivalent rare-earth dopants differing in ionic radii. A hydrothermal assisted co-precipitation method was used for the preparation of two solid solutions, BaCe0.5Zr0.5-xMxO3 and BaCe0.5Zr0.5-xMxO3 (M = La, Gd, Sm, Y; x = 0.10). The investigation of electrical properties revealed that the conductivity has a strong correlation with the ionic radii of the dopant and its interaction with the mobile protons. In comparison to larger sized dopants, the dopants with smaller ionic radii such as Y3+ has the lower trapping sites for proton, thereby, achieving the higher conductivity of 61.2 mS cm(-1) at 600 degrees C under reducing atmosphere. The space charge quantification through Mott-Schottky approximation showed a negligible variation in barrier potential. However, the inclusion of Ce reduced the defect segregation towards the grain boundary due to the electrostatic interaction which in turn reduced the formation of the space charge layer thereby improving the conductivity. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Introducing trivalent rare-earth dopants in barium cerate-zirconate solid solution can modulate grain boundary resistance and enhance protonic conductivity. Doping with smaller ionic radii allows for lower proton trapping sites, achieving higher conductivity.