New Mixed conductors with K2NiF4-type structure

yO4+δ ( A= Sr; B= Cu, Co) oxides with K2NiF4 structure, which can be described as a stacking of perovskite layers alternating with LaO rock salt layers. These compounds have shown to exhibit a wide range of oxygen over-stoichiometry, which involves a considerable improvement of the transport properties. We have studied the structural evolution across different series obtained either by suitable chemical doping or by annealing under high O2-pressure conditions. K2NiF4-type compounds are receiving considerable attention owing to their potential application as mixed conductors at high temperatures. The crystal lattice of K2NiF4 structures can be described as a stacking of perovskite layers alternating with LaO rock salt layers (1). These compounds have shown to exhibit a wide range of oxygen over-stoichiometry, which involves a considerable improvement of the transport properties (2). These is due to their capability to accommodate interstitial oxygen in the LaO rock salt layers.