The preparation and properties of CeB6, SmB6, and GdB6

Single crystals of CeB6, SmB6, and GdB6 have been prepared by a floating-zone technique under a pressurized gas atmosphere of Ar. A zone leveling technique has successfully been applied to prepare single crystals of GdB6, a compound which peritectically decomposes. The crystals so obtained were almost stoichiometric and had a low-impurity level. The measured work functions of (001) surfaces of CeB6 and GdB6 are 2.6±0.1 and 3.8±0.1 eV, respectively. The temperature dependence of the electrical resistivity of CeB6 resembles that of CeAl3. The temperature dependence of the resistivity of SmB6 single crystals is like that of a semiconductor and is similar to those reported for polycrystalline specimens. The resistivity has a very high saturation value of 70.7 Ω cm at low temperatures. A new phase transition of GdB6 was observed at about 7 K, which is indicated by hysteretic behavior in the resistivitiy versus temperature curve.