Synthesis and Characterization of Calcium hexaboride

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.1,2 CaB6 has found application as a high-temperature material, used for surface protection, and as a wear-resistant material.1,2 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, 5 undoped CaB6 6, and CaB2C2 7 have attracted much attention because of their 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.8,9 There is no agreement, however, as to whether the ferromagnetism is extrinsic or intrinsic,10-12, and whether CaB6 is semimetallic13-15 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 reduction of calcium oxide (CaO) with B at 1200-1800 °C in a vacuum, three and by reaction of calcium chloride (CaCl2) with sodium borohydride (NaBH4) at 500 °C in an autoclave for eighth.23 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 Calcium hexaboride, or if you require the latest price of Calcium hexaboride, please feel free to email contact mis-asia.

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