The antimony-rich parts of the ternary systems calcium, strontium, barium and cerium with iron and antimony;: structure refinements of the LaFe4Sb12-type compounds SrFe4Sb12 and CeFe4Sb12;: the new compounds CaOs4Sb12 and YbOs4Sb12

The phase equilibria in the antimony-rich corner of the ternary systems Ca (Sr, Ba, Ce)-Fe-Sb were investigated for the isothermic sections at 900 degrees C. The four corresponding polyantimonides crystallizing with the cubic LaFe4P12 (filled skutterudite)-type structure as well as CeFeSb2 and Ce2Fe4Sb5 an confirmed. The crystal structures of SrFe4Sb12 and CeFe4Sb12 were refined from single-crystal data to conventional residuals of 0.014 and 0.016, respectively. The strontium and the cerium positions are occupied only to 93.5(5) and 89.2(4)%, respectively. In addition, these atoms have relatively large thermal parameters at room temperature, suggesting displacive phase transitions at lower temperatures. The LaFe4Sb12-type compounds CaOs4Sb12 (a=932.1(1) pm) and YbOs4Sb12 (a=931.6 (1) pm) were prepared for the first time. (C) 1999 Elsevier Science S.A. All rights reserved.