Calcium Hexaboride CaB6 Powder CAS 12007-99-7

About Calcium Hexaboride CaB6 Powder:

Calcium hexaboride or calcium boride is a compound of calcium and boron. Calcium boride chemical formula is CaB6. Due to its high conductivity, hardness, chemical stability, and melting point, it is an important material. Calcium boride powder is a black, shiny, chemically inert powder with low density. It has a typical cubic structure of six metal borides, with octahedral units of six boron and calcium atoms.

CaB6 has been investigated due to various peculiar physical properties, such as superconductivity, valence fluctuation, and Kondo effects. However, the most remarkable property of CaB6 is its ferromagnetism. It occurs at unexpectedly high temperatures (600K) and with a low magnetic moment. This high-temperature ferromagnetism originates from the ferromagnetic phase of the dilute electron gas, linkage to the presumed excitonic state in calcium boride, or external impurities on the sample's surface. The impurities might include iron and nickel, probably coming from impurities in the boron used to prepare the sample. 

CaB6 calcium boride is insoluble in H2O, MeOH (methanol), and EtOH (ethanol) and dissolves slowly in acids. Its microhardness is 27 GPa, Knoop hardness is 2600 kg/mm2, the Young modulus is 379 GPa, and electrical resistivity is greater than 2·1010 Ω·m for pure crystals. CaB6 is a semiconductor with an energy gap estimated at 1.0 eV. The low, semi-metallic conductivity of many CaB6 samples can be explained by unintentional doping due to impurities and possible non-stoichiometry.

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Product Performance of Calcium Hexaboride CaB6 Powder:

Calcium boride has the characteristics of high melting point and high hardness. Its physical and chemical properties are quite stable. When calcined in air, sub-micron CaB6 will only gain weight after 800 degrees Celsius and is not easy to oxidize. CaB6 is generally insoluble in hydrochloric acid and sulfuric acid, so technically, to remove impurity materials with hot hydrochloric acid, but CaB6 is soluble in nitric acid.

How is Calcium Hexaboride CaB6 Powder produced?

One of the main reactions of industrial production is:

CaO + 3 B2O3 + 10 Mg→CaB6 + 10 MgO

Other methods of producing CaB6 powder include:

Calcium or calcium oxide reacts directly with boron at 1000°C;

Ca + 6B→CaB6

Ca(OH)2 reacts with boron under a vacuum of about 1700°C (carbothermal reduction);

Ca（OH）2 + 7B→CaB6 + BO（g）+ H2O（g）

The reaction of calcium carbonate and boron carbide under vacuum above 1400°C (Carbothermal reduction)

CaO and H3BO3 react with Mg to 1100°C.

Low-temperature (500°C) synthesis

CaCl2 + 6NaBH4→CaB6 + 2NaCl + 12H2 + 4Na

As a result, the material quality is relatively poor.

To produce, for example, pure CaB6 single crystals used as cathode materials, the CaB6 powder thus obtained is further recrystallized and purified by zone melting technology. The typical growth rate is 30 cm/h, and the crystal size is about 1x10 cm.

Single crystal CaB6 nanowires (diameter 15-40 nm, length 1-10 microns) can be obtained by pyrolyzing diborane (B2H6) on calcium oxide (CaO) powder at 860-900°C in the presence of Ni catalyst.

Application of Calcium Hexaboride CaB6 Powder:

1. Used as a boron-containing additive for dolomite charcoal and magnesium dolomite charcoal refractories to resist oxidation erosion and improve thermal strength.

2. Used as a deoxidizing and degassing agent for highly conductive red copper to improve conductivity and strength.

3. Used as a new material for preventing neutrons in the nuclear industry.

4. Used as a new type of semiconductor material in spin electronic components with a temperature of 900K.

5. Used as a raw material for manufacturing boron trichloride (BCl3) and amorphous boron.

6. Used as a raw material for manufacturing high-purity metal borides (TiB2, ZrB2, HfB2, etc.) and high-purity boron alloys (Ni-B, Co-B, Cu-B, etc.).

7. Used to manufacture a mixture of catalyst-containing calcium-boron nitride (Ca3B2N4) and hexagonal boron nitride and to produce crystal cubic boron nitride with excellent performance.