CRYSTAL-STRUCTURE OF SOME PHASES AND ALLOYING BEHAVIOR IN ALKALINE-EARTHS, EUROPIUM AND YTTERBIUM PNICTIDES

Four phases were synthesized and their crystal structures determined b y powder diffraction methods. Sr11Sb10 (a=12.581(2), c=18.098(4) angst rom) and Sr11Bi10 (a=712.801(3), c=18.451(6) angstrom), 14/mmm, are Ho 11Ge10-type; CaBi2 (a=4.701(2), b=17.053(6), c=4.613(2) angstrom) and EuBi2 (a=c=4.720(3), b=17.11(2) angstrom), Cmcm, are ZrSi2-type. The c rystal structure of a fifth compound Sr2Bi3 was determined by single c rystal diffractometry: M(r)=802.18, orthorhombic, Pnna, a=15.631(5), b =6.793(2), c=6.599(2) angstrom, V=700.7(4) angstrom3, Z=4, D(x)=7.60 M g m-3, R=0.051 with 536 observed reflections. Sr2Bi3 is of a new type and is closely related to the monoclinic Sr2Sb3 and Ca2As3 structures. The binary phases formed by Ca, Sr, Ba, Eu, Yb with As, Sb, Bi are re ported in graphical form and discussed in terms of the size ratio.