Complications Symmetry Reduction, Doping, Mixed Site Occupancy

4 Complications (Symmetry Reduction, Doping, Mixed Site Occupancy) 

The mobihty of protons is not only very sensitive toward reduction of the crystallographic symmetry but also toward local structural and chemical perturbations induced by the aeeeptor dopant or by mixed occupaney on the B site. To allow for the formation of protonic defects by dissociative absorption of water, perovskite-type oxides are eommonly doped with aliovalent ions (aeeeptor dopants) matching the ionie radius of the B-site cation (e.g., In for Zr ). Indeed, this simple concept has been proven successful, e.g., for oxide ion conductors (Sc-doped zirconia shows higher oxide ion eonduetivity than 

In an attempt to calculate association energies for the formation of clusters of protonic defects and different kinds of acceptor dopants in SrCe03-based proton conductors [44], the lowest energies have been found for Y and Yb, the most commonly used dopants for this type of compound. For CaZrOs, the most favorable dopants are anticipated to be Ga, Sc, and In [45] Even interaction of protonic defects with residual oxide ion vacancies has been anticipated to influence the local proton dynamics in SrTiOs [20]. 

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