Chemical strain in perovskite-like materials

Conference Dates

March 10-14, 2019


Pseudo-cubic perovskites based upon substituted oxides RBO3-δ as well as double perovskites RBaB2O6-δ and Sr2BMoO6, where R=rare-earth element and B=3d-transition metal, with A-site and B-site, respectively, cation ordering are very promising materials for a variety of different devices for moderate high temperature applications. The unique feature of the oxides is their ability to undergo both thermal strain and that induced by the defects of oxygen nonstoichiometry in the oxide crystal lattice. The latter is called as chemical or defect-induced strain, which is extremely sensitive to the defect structure of the oxide material. This property was shown recently to be isotropic for pseudo-cubic perovskites unlike that of double perovskites. The crystal lattice of a double perovskite expands along a-axis and simultaneously contracts along c-axis with the decreasing lattice oxygen content. The model of the oxide lattice chemical strain based on a change of mean ionic radius due to reduction of most reducible cation has been recently developed by us. In this work we introduced the new feature in the model such as change of preferable coordination of cations caused by change of oxygen content in the oxide.

The modified model was shown to enable correct prediction of chemical expansion upon increasing oxygen nonstoichiometry along a-axis for both pseudo-cubic and double perovskite oxides and simultaneous lattice contraction along c-axis in double perovskites. Thus most important finding is that simultaneous lattice contraction along c-axis in double perovskites is caused by aforementioned change of preferable coordination.

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