Defect Chemistry in Proton-Conducting Perovskites

The defects in doped BaCe03 perovskites, which are good proton conductors, are described here [32,33,48-54]. It has been recognized that temperature and atmosphere significantly affect the transport properties of the majority of protonic conductors [33], Certainly, under a definite temperature range and specific atmosphere, doped BaCe03 has significant protonic conductivity [48-54], 

The introduction of defects into the perovskite structure and their distribution in the structure are key factors that determine the protonic conductivity [50,51], The inclusion of trivalent dopants ideally takes place, as described in the Kroger-Vink notation, [43] by 

Cece is a neutral (with respect to the lattice) Ce4+ cation in a lattice site Oo is a neutral (as well with respect to the lattice) O2- anion in a lattice site 

Mce is the doping metal M3+ included in the lattice which has a unitary positive charge with respect to the lattice 

The introduction of protons into the perovskite is typically carried out with the help of gas streams containing H20 (g) or H2. Applying the Kroger-Vink notation again, it is possible to describe that the oxygen vacancies, V , react with water to fill lattice positions with oxide ions, Oo, and produce interstitial protons, H, according to [53,54] 

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