New ternary compounds MxTa11-xGe8 (M=Ti, Zr, Hf): Structure and stabilization

摘要

The title compounds MxTa11 Ge-x(8) (M = Ti, Zr, Hf) were prepared from the pure elements by arc-melting and subsequent induction heating at temperatures between 1200degreesC and 1400degreesC. 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 < 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 Huckel calculations performed on hypothetical binary Ta11Ge8. (C) 2002 Elsevier Science (USA). [References: 21]