Oxygen vacancy segregation and space-charge effects in grain boundaries of dry and hydrated BaZrO3

TL;DR

This paper models how oxygen vacancies segregate at grain boundaries in BaZrO3 and how this affects electrostatic barriers and proton conductivity, combining theoretical and computational approaches.

Contribution

It introduces a space-charge model for vacancy segregation in BaZrO3 and provides density-functional calculations for specific grain boundaries.

Findings

Oxygen vacancy segregation influences grain boundary electrostatic barriers.

Segregation explains low proton conductivity in BaZrO3.

Density-functional results support segregation effects.

Abstract

A space-charge model is applied to describe the equilibrium effects of segregation of double-donor oxygen vacancies to grain boundaries in dry and wet acceptor-doped samples of the perovskite oxide BaZrO3. The grain boundary core vacancy concentrations and electrostatic potential barriers resulting from different vacancy segregation energies are evaluated. Density-functional calculations on vacancy segregation to the mirror-symmetric \Sigma 3 (112) [-110] tilt grain boundary are also presented. Our results indicate that oxygen vacancy segregation can be responsible for the low grain boundary proton conductivity in BaZrO3 reported in the literature.