Stabilization of high transition metal valencies and correlations with electronic properties of oxides with the perovskite structure

Abstract

The stabilization of the highest oxidation states of transition metals is directly correlated (i) with different factors characterizing the local surrounding of the M element (symmetry and chemical bonding), and (ii) with the oxygen pressure used for the synthesis of the corresponding oxides.

For a M ⁿ⁺ transition ion, the increase of n induces a strong improvement of the strength of the M ⁿ⁺-O bond and consequently a change of the physico-chemical properties of the corresponding oxygen lattices.

Two electronic phenomena have been particularly studied: (i) the change of electronic configurations [low-spin → high-spin of cobalt (III)], (ii) the Fe(IV) disproportionation [2Fe(IV) → Fe(III) + Fe(V)].