Acceptor-doped perovskite oxides

De Souza, R.A., Kilner, J.A., and Steele, B.C.H. (1995) A SIMS study of hydrogen in acceptor-doped perovskite oxides. Solid State Ionics, 77, 180-184. 

The acceptor-doped perovskites (general formula of ABOs-a) have shown much promise as MIECs. Much attention has been focused on these versatile metal oxides as they exhibit catalytic activity [24] and therefore their use in some applications can avoid the need for catalytic modification of the membrane surface. This activity has meant that MIECs can be used as electrode materials in solid-oxide fuel cell systems for the reduction of oxygen simultaneously, this inherent catalytic activity means that problems with chemical stability can arise. 

V. Acceptor-Doped Perovskite and Perovskite-Related Oxides A. Introduction... 

V. ACCEPTOR-DOPED PEROVSKITE AND PEROVSKITE-RELATED OXIDES... 

R.A. De Souza, A Universal Empirical Expression for the Isotope Surface Exchange Coefficients (k ) of Acceptor-Doped Perovskite and Fluorite Oxides . Phys. Chem. Chem. Phys. 8, 890-897 (2006)... 

Proton Conductivity in Acceptor-Doped Perovskites 11.2.1 Protons in Oxides... 

Materials with high proton or oxide ion conductivity are widely studied for their potential application as electrolytes in fuel cells, electrolysers, batteries, sensors, ete. [1-5], Acceptor doped perovskite-type oxides ABO3.5 where A is Sr, Ba and B is Ce, Zr are well-known high temperature proton conductors in wet atmosphere. It was found that the main factor responsible for the appearance of protons in the structure was the presence of oxygen vacancies. Upon hydration by equilibration with water vapor the oxygen vacancies may be filled by oxygen from water and, in accordance with dissociative mechanism of water dissolution, the hydroxide ions are formed. In this case the dissolution of water may be written [6] ... 

Exactly the opposite occurs, namely the conversion of an ex situ parameter to an in situ one, if foreign components become sufficiently mobile. The corresponding incorporation reaction then becomes reversible. Under such conditions it is natiurally better to speak of solubility equihbria. Important examples are segregation equilibria of impurities at very high temperatures, another refers to the incorporation of protonic defects in oxides by the dissolution of H2O. Materials interesting in this respect are CaO-doped Z1O2 [196] or acceptor-doped perovskites [197], such as the Fe-doped SrTiOs discussed above. (As before we regard the acceptor dopant... 

Acceptor doping in perovskite oxides gives materials with a vacancy population that can act as proton conductors in moist atmospheres (Section 6.9). In addition, the doped materials are generally p-type semiconductors. This means that in moist atmospheres there is the possibility of mixed conductivity involving three charge carriers (H+, O2-, and h ) or four if electrons, e, are included. 

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