SYNTHESIS AND CRYSTAL-STRUCTURE DETERMINATION OF LAAUO3

A new ternary oxide of gold and lanthanum, LaAuO3, has been prepared from Au2O3 · 2H2O and La(OH)3 by applying high oxygen pressure and adding aqueous KOH (55%) as a mineralizer. The bright yellow and diamagnetic LaAuO3 crystallizes in the orthorhombic crystal system, Pbcm, a = 403.35(7), b = 1307.3(2), c = 569.52(8) pm, Z = 4. The crystal structure (determined from 980 unique reflections with a final R value of 5.7% (Rw = 4.7%)) consists of a grid of cubes formed by the oxygens which are either centered by lanthanum ions or face centered by gold ions. Thus, lanthanum is coordinated eightfold, and gold fourfold, by oxygen. LaAuO3 may be described as a CaF2 structure sheared within the (110) plane by half a translational period along (0 0 1]. © 1993 Academic Press, Inc.