Preparation
- One of the main reactions for industrial production is:
- CaO + 3 B2O3 + 10 Mg → CaB6 + 10 MgO
Other methods of producing CaB6 powder include:
- Direct reaction of calcium or calcium oxide and boron at 1000°C;
- Ca + 6B → CaB6
- Reacting Ca(OH)2 with boron in vacuum at about 1700 °C (carbothermal reduction);
- Ca(OH)2 +7B → CaB6 + BO(g) + H2O(g)
- Reacting calcium carbonate with boron carbide in vacuum at above 1400 °C (carbothermal reduction)
- Reacting of CaO and H3BO3 and Mg to 1100°C.
- Low-temperature (500 °C) synthesis
- CaCl2 + 6NaBH4 → CaB6 + 2NaCl + 12H2 + 4Na
results in relatively poor quality material.
- To produce pure CaB6 single crystals, e.g., for use as cathode material, the thus obtained CaB6 powder is further recrystallized and purified with the zone melting technique. The typical growth rate is 30 cm/h and crystal size ~1x10 cm.
- Single-crystal CaB6 Nanowires (diameter 15-40 nm, length 1-10 micrometres) can be obtained by pyrolysis of diborane (B2H6) over calcium oxide (CaO) powders at 860-900 °C, in presence of Ni catalyst.
Read more about this topic: Calcium Hexaboride
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