Oxygen incorporation in acceptor-doped perovskites
Oxygen incorporation in acceptor-doped perovskites
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DOI：
10.1103/physrevb.83.174101
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发表时间：
2011-05-02
影响因子：
3.7
通讯作者：
Geneste, Gregory
中科院分区：
文献类型：
--
作者：
Bevillon, Emile;Dezanneau, Guilhem;Geneste, Gregory
Oxygen is experimentally known to be incorporated in acceptor-doped perovskites at high temperatures, leading to a hole conductivity proportional to p(O2)(1/4) and increasing with temperature [1/2O(2) + V-O(center dot center dot) -> O-O(X) + 2h(center dot)]. Either this high-temperature incorporation is thermodynamically favored by temperature, suggesting an endothermic process (Delta H-0 > 0), or it is exothermic. In the latter case, since it is obviously associated with a Delta S-0 < 0, the process should be favorable only at low temperatures, except if kinetically blocked. To examine this phenomenon, the reaction of O-2 incorporation into the acceptor-doped perovskites BaSnO3 and BaZrO3, doped by trivalent dopants (Ga, Sc, In, Y), according to BaSn/Zr1-x MxO3 (x/2) + x/4O(2) -> BaSn/Zr1-x MxO3, is studied by density-functional calculations for a high dopant concentration (x = 0.25). In this process, the charged vacancies V-O(center dot center dot) resulting from the charge compensation produced by doping, are filled with oxygen atoms, yielding a metallic compound with holes. It is found to be exothermic in all cases, showing that these acceptor-doped perovskites are able to incorporate oxygen at low temperatures, whereas the reaction is unfavorable above a given temperature, whose value is discussed. At any rate, it is suggested that the process is kinetically blocked at low temperatures due to very slow thermally activated vacancy diffusion. A thermochemical approach is presented that tentatively explains why the hole conductivity increases with temperature at high temperatures, although the hole concentration decreases, yielding a model compatible with experimental observations and theoretical calculations.
