NEW TERNARY COPPER PNICTIDES WITH MODIFIED BAAL4 TYPE STRUCTURES

EuCu2As2 (a = 4.215(1) Angstrom, c = 10.185(2) Angstrom) and EuCu2Sb2 (a = 4.504(1) Angstrom, c = 10.824(2) Angstrom) were prepared by heating (900 degrees C) mixtures of CuCl and arsenic (antimony) with europium. The by-products were dissolved by dilute acetic acid. The arsenide crystallizes in the ThCr2Si2 type structure (($) over bar 14/mmm; Z = 2) with holes in the copper arrangement, whereas the antimonide forms the CaBe2Ge2 type structure (P4/nmm; Z = 2). The stability ranges of both phases were determined by mixed crystal formation in accordance with EuCu2As2-xSbx. Magnetic measurements showed, that Europium is divalent and that the compounds order magnetically at low temperatures. BaCu2Sb2 (($) over bar 14/mmm; a = 4.655(1) Angstrom, c = 32.709(6) Angstrom; Z = 6) was prepared by heating a mixture of binary antimonides of barium and copper in a melt of NaCl/KCl. The structure of this compound consists building elements of the CaBe2Ge2 and the ThCr2Si2 type structure. The already known compounds SrCu2As2 and BaCu2As2 were produced in a homogeneous form for the first time and their structures (ThCr2Si2 type) redetermined by means of single crystal X-ray methods.