Three novel Zintl phases in the magnesium-lanthanum-antimony system based on intergrowth of LaSb and Mg<SUB>3</SUB>Sb<SUB>2</SUB> slabs

Reactions of the elements in welded Ta containers at 875-1050°C produce the black brittle compounds Mg4.5La4;9Sb7 (5-4-7), Mg4.6La3Sb6 (5-3-6), and Mg1.7La4.9Sb6 (2-5-6). All three consist of coherent intergrowths of Mg5Sb4 (in 5-4-7 and 5-3-6) or Mg2Sb2 (2-5-6) slabs derived from Mg3Sb2 (3-0-2) (anti-α-La2O3) with Lan+1Sbn slabs from LaSb (NaCl-type) for n=3, 2, and 4, respectively, in which a layer of (111) La replaces octahedral (001) Mg at the interface