Evolution structurale sous haute pression des phases K2MO3 (M = Zr,Hf, Sn,Pb)

The study of the high-pressure modifications of the oxides K₂MO₃ (M = Zr, Hf, Sn, Pb) confirms the tendency of potassium to adopt the trigonal prismatic coordination in layer oxides: The β form is characterized by layers of (K, M)O₆ octahedra with common edges, between which other potassium atoms are inserted with prismatic coordination. For M = Zr and Hf, an increase of pressure or temperature transforms β to the γ or δ variety, both derived from the NaCl structure. The influence of the electronegativity of M on the potassium coordination in layer structures is discussed.