Abstract
The cubic hexaborides, RB6, have long attracted interest for their wide variety of physical properties which are caused by the metal cations, R2+ or R3+. However, looking at them from a viewpoint of materials, the three-dimensional boron-framework also plays an important role. For example, in the case of LaB6 thermionic electron emitters, the boron-framework causes the low vapor pressure and makes it possible to prepare the high quality crystals. Therefore, in this report, we paid attention to the boron-framework of the alkaline-earth and the rare-earth hexaborides, CaB6, SrB6, BaB6, LaB6 and YB6, and refined their crystal structure by a four-circle diffractometer with Mo Ka. In addition, we discuss force-constants the boron atoms, the thermal expansion and the high-temperature microhardness.
