  Thermal expansion of MAX phases along different directions tended to be
different because of the anisotropy of hexagonal crystals. Herein, a new Hf2SeC
phase was synthesized and confirmed to be relatively isotropic, whose
coefficients of thermal expansion (CTEs) were determined to be 9.73 {\mu}K-1
and 10.18 {\mu}K-1 along a and c directions. The strong M-S bond endowed Hf2SC
and Zr2SC lower CTEs than Hf2SeC and Zr2SeC. A good relationship between the
thermal expansion anisotropy and the ratio of elastic stiffness constant c11
and c33 was established. This straightforward approximation could be used to
roughly predict the thermal expansion anisotropy of MAX phases.
