The effect of dopant at the Zr site on the proton conduction pathways of SrZrO3: An orthorhombic perovskite

Doping orthorhombic SrZrO3 at 12.5% of the Zr sites with Al3+ leads to a local squaring of the lattice, while doping with larger Y3+ increases local octahedral distortions. Proton activation energy barriers and transition state theory prefactors are calculated. The wide range of intra-, inter-, and rotational barriers suggest that a comprehensive pathway analysis is needed to find the limiting conduction barriers. Simple seven to ten step periodic pathways leading to system wide conduction are enumerated using vertex coding. At 900-1300 K, the average limiting barriers to long range conduction are 0.6 and 0.4 eV in Al/SrZrO3 and Y/SrZrO3, respectively, in reasonable agreement with the experiment. Path analysis gives the added insight that conduction pathways in Al/SrZrO3 avoid doped regions, while conduction pathways in Y/SrZrO3 traverse them. (C) 2010 American Institute of Physics. [doi:10.1063/1.3471798]