Anisotropic thermal expansion of MgSiN2 from 10 to 300 K as measured by neutron diffraction

The lattice parameters of orthorhombic MgSiN2 as a function of the temperat ure have been determined from time-of-flight neutron powder diffraction. Th e results indicate that MgSiN2, just like several other adamantine-type cry stals, exhibits a relatively small thermal expansion coefficient at low tem peratures. This is ascribed to a strongly bonded 3D, relatively open, cryst al structure which is characteristic of highly covalent bonded materials. T he anisotropic linear thermal expansion behaviour could be qualitatively re lated to the characteristics of the crystal structure. The least dense pack ed crystallographic direction showed the smallest anisotropic linear expans ion coefficient. (C) 2000 Elsevier Science Ltd. All rights reserved.