New Ternary Compounds MxTa 11− xGe 8 ( M=Ti, Zr, Hf): Structure and Stabilization

Abstract

The title compounds M x Ta 11− x Ge 8 ( M=Ti, Zr, Hf) were prepared from the pure elements by arc-melting and subsequent induction heating at temperatures between 1200°C and 1400°C. X-ray powder diffraction studies of the samples were performed using the Guinier technique and the respective powder patterns were refined with a structure model based on the orthorhombic Cr 11Ge 8-structure type ( oP76, Pnma). The homogeneity ranges of the compounds were determined to be 0.9< x<1.3 ( M=Ti), 0.7< x<1.3 ( M=Zr) and 0.7< x<2.4> ( M=Hf) by means of electron probe microanalysis. Chemical bonding, electronic structure and site preferences are discussed based on extended Hückel calculations performed on hypothetical binary Ta 11Ge 8.