Perovskites providing mobile oxygen

In this structure there are perovskite layers of ABO3 separated by AO rock salt layers. It is this layered structure that allows great flexibility in the oxygen stoichiometry of these materials. It is possible to incorporate excess oxygen (5 > 0) in the unusual form of interstitial oxygens, which provide an alternative to the vacancy-based conduction mechanism present in the perovskite and fluorite oxides, where the dopant-vacancy interactions can limit the observed conductivity. The mobility of the oxide ions in these materials occurs mainly through an interstitialcy mechanism in the aZ)-plane, although evidence of low Ea for the conduction in the c-direction via a Frenkel mechanism has also been reported. ... 

It is well known that the major limitation of the application of perovskites as combustion catalysts is their lower surface area and their increased tendency to sinter. One solution to increase the contact surface between the VOC and the perovskite is to disperse it on a large surface area and thermally stable support. Thus, supported LaCoOs perovskites on CeZr02 have been studied recently. The use of a CeZr02 support for lanthanum cobalt perovskites promoted the catalytic activity with respect to the corresponding bulk perovskites, decreasing the temperature for complete toluene oxidation by more than 50 C. The increased activity was related to two factors (i) the larger exposed surface and (ii) the composition of the support which provided the increased oxygen mobility of the catalyst. 

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