Isostructural substitution, of cations

One of the most useful properties of perovskites is their ability to incorporate mixed valences into their structure. It is worth noticing that conjugated mixed valence systems extensively occur in very important redox catalytic systems in nature, the most celebrated one perhaps being photosystem 11 in plants. This system contains mixed valence states of Mn and is responsible for water splitting and oxygen evolution, which is one of the most important reactions on our planet So the creation of mixed valences in perovskites bears strong elements of biomimicry. The routes for creating such mixed valences may be either structure deficiencies or isostructural substitution of cations into a mother structure. 

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