Identification and characterisation of three novel compounds in the sodium–aluminium–oxygen system

Abstract

Reactions of sodium oxide with α-Al₂O₃ have produced three novel sodium-rich aluminates, Na₇Al₃O₈(triclinic, space group P), Na₁₇Al₅O₁₆(monoclinic, space group Cm), and Na₅AlO₄(orthorhombic, space group Pbca). X-Ray crystal structure determinations have shown Na₇Al₃O₈ to consist of infinite double chains composed of Al₆O₁₆ rings linked by oxygen bridges, Na₁₇Al₅O₁₆ to consist of discrete Al₅O₁₆ chains of corner-sharing AlO₄ tetrahedra with almost linear angles about the bridging oxygens, and Na₅AlO₄ to be composed of isolated AlO₄ tetrahedra.