New Ternary Compounds MxTa11-xGe8 (M=Ti, Zr, Hf): Structure and Stabilization

The title compounds MxTa11-xGe8 (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 Cr11Ge8-structure type (oP76, Pnma). The homogeneity ranges of the compounds were determined to be 0.9 (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 Ta11Ge8.