Thermal expansion of microand nanocrystalline $\rm HfB_2$

Hafnium diboride nano- and microcrystals are studied by high-temperature X-ray diffraction in the temperature range of $300$–$1500$ K. $\rm HfB_2$ nanocrystals are found to have a greater thermal expansion coefficient than $\rm HfB_2$ microcrystals. The thermal expansion of $\rm HfB_2$ is found to be anisotropic with respect to the unit cell axes.