Thermal expansion anisotropy of ternary molybdenum silicides based on (formula presented)

The coefficient of thermal expansion (CTE) of the tetragonal silicide (formula presented) is highly anisotropic. The ratio of the CTE’s in the c and a directions, (formula presented) is approximately 2. Partial substitution of the Mo in (formula presented) by “larger” Nb or “smaller” V atoms increases or reduces the lattice parameters, respectively. In both cases the CTE anisotropy (formula presented) decreases significantly and values as small as 1.25 are observed. Similar results have been reported previously for (formula presented) alloyed with “large” Zr atoms and for (formula presented) alloyed with “small” Ti atoms. These results are interpreted in terms of the site occupation of the ternary alloying additions and the resulting reductions in the anharmonicity along the c axis.