  The lattice parameters of two boron subnitrides, B13N2 and B50N2, have been
measured as a function of temperature between 298 and 1273 K, and the
corresponding thermal expansion coefficients have been determined. Thermal
expansion of both boron subnitrides was found to be quasi-linear, and the
volume thermal expansion coefficients of B50N2 (15.7(2) 10-6 K-1) and B13N2
(21.3(2) 10-6 K-1) are of the same order of magnitude as those of boron-rich
compounds with structure related to {\alpha}-rhombohedral boron. For both boron
subnitrides no temperature-induced phase transitions have been observed in the
temperature range under study.
