Lattice expansions of two boron carbides between 12 and 940°C

High-temperature X-ray diffraction methods have been used to determine unit-cell parameters of two boron carbide compositions from 12° to about 940°C. One composition was at the carbon-rich end of the phase field (i.e. B₄C), the second at the boron-rich end (5 at. % C by chemical analysis). The lattice expansion of both substances was isotropic in the temperature range studied. The mean linear thermal expansion coefficient for the carbon-rich composition is 5.65 x 10^-6°C^-1, while that of the boron-rich composition is 5"87 x 10^-6°C^-1.