The hexagonal form corresponding to graphite is the most stable and soft among BN polymorphs, and is therefore used as a lubricant and an additive to cosmetic products.

[3] Because of excellent thermal and chemical stability, boron nitride ceramics are used in high-temperature equipment and metal casting.

Boron nitride was discovered by chemistry teacher of the Liverpool Institute William Henry Balmain [de] in 1842 via reduction of boric acid with charcoal in the presence of potassium cyanide.

The amorphous form of boron nitride (a-BN) is non-crystalline, lacking any long-distance regularity in the arrangement of its atoms.

The most stable crystalline form is the hexagonal one, also called h-BN, α-BN, g-BN, graphitic boron nitride and "white graphene".

The cubic form has the sphalerite crystal structure (space group = F43m), the same as that of diamond (with ordered B and N atoms), and is also called β-BN or c-BN.

Earlier optimistic reports predicted that the wurtzite form was very strong, and was estimated by a simulation as potentially having a strength 18% stronger than that of diamond.

[8] Its hardness is 46 GPa, slightly harder than commercial borides but softer than the cubic form of boron nitride.

[18] Polycrystalline c-BN with grain sizes on the order of 10 nm is also reported to have Vickers hardness comparable or higher than diamond.

If voltage is applied to h-BN[21][22] or c-BN,[23] then it emits UV light in the range 215–250 nm and therefore can potentially be used as light-emitting diodes (LEDs) or lasers.

The structure of monolayer BN is similar to that of graphene, which has exceptional strength,[29] a high-temperature lubricant, and a substrate in electronic devices.

As in diamond synthesis, to further reduce the conversion pressures and temperatures, a catalyst is added, such as lithium, potassium, or magnesium, their nitrides, their fluoronitrides, water with ammonium compounds, or hydrazine.

The shock wave method is used to produce material called heterodiamond, a superhard compound of boron, carbon, and nitrogen.

[20] Because of its excellent thermal and chemical stability, boron nitride ceramics and coatings are used high-temperature equipment.

[52][53] Hexagonal BN is used in xerographic process and laser printers as a charge leakage barrier layer of the photo drum.

[54] In the automotive industry, h-BN mixed with a binder (boron oxide) is used for sealing oxygen sensors, which provide feedback for adjusting fuel flow.

Owing to their hexagonal atomic structure, small lattice mismatch with graphene (~2%), and high uniformity they are used as substrates for graphene-based devices.

[57] h-BN has been used since the mid-2000s as a bullet and bore lubricant in precision target rifle applications as an alternative to molybdenum disulfide coating, commonly referred to as "moly".

[64] Its usefulness arises from its insolubility in iron, nickel, and related alloys at high temperatures, whereas diamond is soluble in these metals.

[51] Similar to diamond, the combination in c-BN of highest thermal conductivity and electrical resistivity is ideal for heat spreaders.

As cubic boron nitride consists of light atoms and is very robust chemically and mechanically, it is one of the popular materials for X-ray membranes: low mass results in small X-ray absorption, and good mechanical properties allow usage of thin membranes, further reducing the absorption.

The synergic effect of the atomic thickness, high flexibility, stronger surface adsorption capability, electrical insulation, impermeability, high thermal and chemical stability of BN nanosheets can increase the Raman sensitivity by up to two orders, and in the meantime attain long-term stability and reusability not readily achievable by other materials.

[77][78] Atomically thin hexagonal boron nitride is an excellent dielectric substrate for graphene, molybdenum disulfide (MoS2), and many other 2D material-based electronic and photonic devices.

Cai et al., therefore, conducted systematic experimental and theoretical studies to reveal the intrinsic Raman spectrum of atomically thin boron nitride.

It consists of a single BN layer, which forms by self-assembly a highly regular mesh after high-temperature exposure of a clean rhodium[82] or ruthenium[83] surface to borazine under ultra-high vacuum.

It can have a density as low as 0.6 mg/cm3 and a specific surface area as high as 1050 m2/g, and therefore has potential applications as an absorbent, catalyst support and gas storage medium.

[95] It offers better performance characteristics including Superior corrosion and erosion resistance over a wide temperature range.

[105] PBN material has been widely manufactured as crucibles of compound semiconductor crystals, output windows and dielectric rods of traveling-wave tubes, high-temperature jigs and insulator.

[106] Boron nitride (along with Si3N4, NbN, and BNC) is generally considered to be non-toxic and does not exhibit chemical activity in biological systems.

[107] Due to its excellent safety profile and lubricious properties, boron nitride finds widespread use in various applications, including cosmetics and food processing equipment.