NEW TERNARY CLATHRATE COMPOUNDS IN THE SYSTEMS BARIUM INDIUM/ZINC/CADMIUM GERMANIUM - ZINTL COMPOUNDS WITH PHASE WIDTH

By systematic investigations in the systems barium-indium/zinc/cadmium-germanium we found couple of new electrovalent ternary compounds with A(8)X(46) clathrate (I) type structures. They crystallize cubically in space-group Pm3n. For Ba8In16Ge30 (a = 1075.8 pm), Ba8Zn8Ge38 (a = 1082.0 pm) and Ba8Cd8Ge38 (a = 1096.0 pm) the structures were verified by X-ray single crystal diffraction data. According to valence and bounding distances the new clathrates should be Zintl compounds. Measurements of the temperature dependence of the electrical resistivity proved, that they are indeed semiconductors. A part of the 2B/3B metal atoms can be substituted by germanium. Charge balance will be retained by creation of vacancies in the A(8)X(46) type structures. By phase analysis the limits of the composition range were determined as Ba8In4Ge9[]Ge-3(30) (a=1084.9pm), Ba8Zn4Ge10[]Ge-2(30) (a = 1073.6 pm) and Ba8Cd4Ge10[]Ge-2(30) (a = 1082.0 pm).