Structure, chemical stability and mixed proton–electron conductivity in BaZr0.9−xPrxGd0.1O3−δ

BaZr0.9−xPrxGd0.1O3−δ (x = 0.3 and 0.6) was prepared by combustion synthesis and characterised with respect to conductivity and stability in an attempt to combine the desirable properties of the end members. The polycrystalline materials exhibit a cubic or pseudo-cubic structure as determined by X-ray synchrotron radiation and transmission electron microscopy. The chemical stability of the compositions is strongly dependent on the praseodymium content, the materials with more Pr present lower stability. Electron holes dominate the conductivity under oxidising atmospheres in BaZr0.3Pr0.6Gd0.1O3−δ, while BaZr0.6Pr0.3Gd0.1O3−δ exhibits a mixed electron hole–proton conducting behaviour. Substitution of Zr by Pr in acceptor-doped BaZrO3 decreases the sintering temperature and increases the grain growth rate.

► Pr can be used in BaZrO3 electrolytes to enhance sinterability and grain growth.
► The average grain size in BaZr0.6Pr0.3Gd0.1O3−δ is 0.8–3 μm after sintering at 1500 °C.
► Ba(Zr,Pr)Gd0.1O3−δ are electron-, mixed electron–proton, or pure proton conductors, depending on composition.