Mestastability of the K2NiF4 - Type structures in Eu2-xSrxNiO4 solid solutions

The results of the crystal chemical investigation of the solid solution Eu2 -xSrxNiO4 are reported. Modeling the chemical bond by the valence bond mode l, we conclude that the substitution Er3+/Sr2+ stabilizes the K2NiF4-like s tructure by the partial oxidation of the Ni2+ ions. Additionally, the resul ts are used to underscore the role of the nine-fold coordination of the Eu3 + / Sr2+ cations as a "mixing" the twelve-fold coordination in EuNiO3 perov skite and the six-fold one of Sr2+ in rock structure of SrO. By increasing the Sr2+ amount, the structure will be stabilized because the bond distance s of the two parts of the nine-fold coordination fend to become appropriate .