Peculiarities of formation of perovskite-like ruddlesden — popper phases based on rare-earth oxides

The dependence of the value of ∆G0n,f (the standard Gibbs free energy of Ruddlesden-Popper RPn phase formation) on the n-value in the series AO∙(ABO3)n (where A = Ca, Sr, Ba, La; B = Co, Ni, Ti, Zr, Hf) was analyzed using the thermodynamic data available in the literature. It is found that the value of ∆G01/n,f for all analyzed systems depends linearly on 1/n. The consequences of the existence of the linear dependence are analyzed from the point of view of carrying out the synthesis of the RPn phases. On the example of strontium-rare-earth cobaltites of the composition (SrxLn1-x)n+1СоnO3n+1 (Ln = Sm, Gd, Dy; n = 2, ), the possibility of obtaining RPn phases with a different character of the distribution of Sr/Ln cations over the A-positions of the crystalline lattice, stabilization conditions for new metastable phases (SrxLn1-x)3Со2O7-, which are absent in the phase diagrams in air, are given.