Single Crystal Calcium Hexaboride Nanowires

Calcium hexaboride (CaB6), one of the divalent alkaline-earth cubic hexaborides, has low density (2.45 g/cm3 ), high melting point (2235 °C), high hardness (Knoop: 2600 kg/ mm2 ), high Young's modulus (379 GPa), and high chemical stability. CaB6 has found applications as a high-temperature material, used for surface protection, and is a wear-resistant material. CaB6 is also a promising candidate for n-type thermoelectric (TE) materials because its power factor has been reported to be larger than or comparable to common TE materials (i.e., Bi2Te3, PbTe, Si1-xGex).3,4 Recently, the discovery of weak ferromagnetism in La-doped CaB6, five undoped CaB6 6, and CaB2C2 7 has attracted much attention because of their respective high Curie temperatures (>600 K) but with the absence of a 3d or 4f element in each compound. The mechanisms for the observed ferromagnetism in these compounds have been explored with both experiment and theory. However, there is no agreement on whether ferromagnetism is extrinsic or intrinsic and whether CaB6 is semimetallic or semiconducting. CaB6 bulk crystals have been prepared at elevated temperatures (>1500 °C) by hot-press sintering,18 the floating zone method,19 and the aluminum flux method.20 CaB6 powders have been prepared by direct combination of boron (B) with calcium (Ca) at 1000 °C in a sealed tantalum crucible,21 by carbothermal reduction of calcium carbonate (CaCO3) and boron carbide (B4C) at 1400 °C and 10-2 Pa,22 by removal of calcium oxide (CaO) with B at 1200-1800 °C in a vacuum,3 and by reaction of calcium chloride (CaCl2) with sodium borohydride (NaBH4) at 500 °C in an autoclave for 8 h. The finest crystalline CaB6 powders synthesized so far have an average size of 180 nm. If you are looking for high quality, high purity, and cost-effective zinc sulfide, or if you require the latest price of zinc sulfide, please feel free to email contact mis-asia.

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