Investigations about the stability range of the CaAl2Si2 type structure in the case of ternary silicides

Five compounds LnAl(2)Si(2) (Ln: trivalent rare-earth metal, Y) were synthesized by heating the elements at 800 degrees-1000 degrees C. They are isotypic and crystallize in the CaAl2Si2 type structure (<P(3)over bar ml>; Z = 1) (lattice constants see "Inhaltsubersicht"). The electronic structures (LMTO band structure calculations) of CaAl2Si2 and YAl2Si2, the latter one is in accordance to Ln(3+)(Al3+)(2)(Si4-)(2) not electrovalent, are discussed with regard to the bondings and the electrical conductivity respectively. Investigations of GdAl2-xMnxSi2 mixed crystals showed, that the structure type already at low Mn content (x approximate to 0,3) changes from CaAl2Si2 (GdAl2Si2) to ThCr2Si2 type structure (GdMn2Si2).