What is Lanthanum hexaboride?
LaB₆ is the chemical formula for lanthanum hexaboride, a compound of lanthanum and boron with CAS number 12008-21-8 and a molecular weight of 203.78 g/mol. It belongs to the metal boride family, a group of materials known for combining high hardness with useful electronic and optical properties.
This boride has a melting point of 2210°C, which makes it one of the most thermally stable materials used in coating and optical applications. The compound forms a single crystal structure with a notably low work function, the energy needed to remove an electron from its surface. This low work function is why LaB₆ has traditionally been used as a hot cathode material. It is used in electron microscopes, electron beam welding equipment, electron lithography systems and X-ray tubes, where a stable, high-intensity electron beam is needed at high temperatures.
Lanthanum hexaboride belongs to a group of refractory metal compounds with properties closer to a metal oxide than to a typical boride. Its free electrons move easily through the crystal lattice, which explains both its electrical conductivity and its strong interaction with infrared light. When LaB₆ nanoparticles absorb infrared rays, this shielding effect is what makes the material useful in thermal protection applications, separate from its role as a hot cathode material.
Partners in Chemicals supplies LaB₆ as nanoparticles for infrared absorption and ultrahard coatings, a newer application that is gaining ground fast.
Why are LaB₆ nanoparticles attracting attention?
Lanthanum hexaboride has been used in scientific instruments for decades, but interest in LaB₆ nanoparticles has grown significantly in recent years. The reason is a combination of properties rarely found together: strong infrared absorption and extreme hardness, in a material that can now be processed at low temperatures thanks to new ink-based coating technology.
This combination makes LaB6 relevant for industries that were previously limited to either hard coatings or infrared-shielding coatings, but rarely both in a single, easy-to-apply layer.
Properties of LaB₆ nanoparticles
LaB6 nanoparticles absorb strongly in the 800 – 1400 nm range, which places them firmly in the near-infrared part of the spectrum. This makes LaB₆ a powerful shielding material against infrared radiation, useful in applications ranging from automotive glass to architectural glazing.
What makes this compound particularly interesting is how little material is needed. LaB₆ nanoparticles work as infrared absorbers in extremely low doses, between 10 and 100 mg per square metre. A coating this thin still provides meaningful infrared shielding, which keeps material costs low and allows for coatings that remain visually transparent.
Lanthanum hexaboride nanoparticles have a Vickers hardness of 2000 HV, equivalent to 19.6 – 22 GPa. This places LaB₆ among the hardest materials used in coating applications, comparable to materials used in wear-resistant industrial coatings.
The combination of high hardness and infrared absorption in a single nanoparticle is what sets this compound apart from many conventional coating materials, which typically offer one property or the other.
LaB₆ ink technology explained
Traditional LaB₆ coatings are applied through high-temperature processes such as chemical vapour deposition (CVD), physical vapour deposition (PVD) or sputtering. These methods require temperatures between 800°C and 1800°C and specialised vacuum equipment, which limits which substrates can be coated and drives up costs considerably.
Partners in Chemicals offers LaB₆ as part of a newly patented ink platform (WO2025063847, Loredana Protesescu et al.) that takes a different approach altogether. The technology uses LaB₆ nanocrystals between 5 and 20 nm in size, combined with innovative ligand engineering, to create soluble nanoparticles formulated as a stable ink.
This ink can be applied through spray coating, dip coating, spin coating or inkjet printing, and dries at temperatures below 90°C. Because the process does not require sintering or vacuum equipment, it opens up coating possibilities that traditional methods cannot offer.
How this compares to conventional coating methods
| Aspect | Conventional methods (CVD/PVD/sputtering) | LaB₆ ink technology |
|---|---|---|
| Temperature | 800 – 1800°C | Drying below 90°C |
| Substrates | Heat-resistant only | Flexible and low-melting substrates |
| Method | Vacuum and expensive equipment | Inkjet, spray, blade coating |
| Integration | Difficult | Direct functional printing |
| Cost and energy | High | Low and scalable |
For more background on the difference between conventional coating techniques and ink-based coating, read our article on CVD, PVD and ink-based coating.
What makes LaB₆ ink different?
The LaB₆ ink can be formulated at high concentrations, up to 50 mg/mL, and remains stable for several months. It is tunable for different solvents and substrates, which makes it adaptable to a wide range of industrial coating processes.
The ink delivers both infrared absorption and wear resistance in a single coating layer, applied through direct printing without the need for sintering.
Low-temperature drying, below 90°C, means the ink can be applied to flexible and heat-sensitive substrates that cannot withstand traditional coating processes.
The ink is compatible with existing industrial printing techniques and offers an energy-efficient, solution-based alternative to vacuum-based coating methods.
Applications
Lanthanum hexaboride is used as a powerful infrared absorber for thermal shielding in automotive glass, architectural glazing and optical coatings. Because the coating remains transparent at the low doses required, it can be applied without significantly affecting visible light transmittance.
In solar control glass, LaB₆ helps reduce heat transmission from sunlight while keeping the glass visually clear. This makes it relevant for both residential and commercial architectural glazing, where reducing cooling costs is a growing priority.
The nanoparticles contribute to improved light management in solar cells, helping them convert more sunlight into energy.
With a hardness of up to 22 GPa, LaB₆ works well for wear-resistant coatings. The low-temperature ink process means this hardness can now be applied to temperature-sensitive materials that could not previously be coated with such hard materials.
The ink platform is compatible with co-injected and coextruded semi-finished products, enabling functional coatings to be integrated directly into manufacturing processes rather than applied as a separate step.
In its traditional application, LaB₆ single crystals continue to be used as hot cathodes in electron microscopes, electron beam welding equipment, electron lithography and X-ray tubes, where a stable electron beam at high temperatures is needed.
Specifications
| Property | Value |
|---|---|
| CAS number | 12008-21-8 |
| Chemical name | Lanthanum hexaboride |
| Molecular formula | LaB₆ |
| Molecular weight | 203.78 g/mol |
| Melting point | 2210°C |
| Hardness | 2000 HV (19.6–22 GPa) |
| IR absorption range | 800 – 1400 nm |
| Particle size (ink) | 5 – 20 nm |
| Ink concentration | Up to 50 mg/mL |
| Ink drying temperature | Below 90°C |
| Dangerous goods | No |
A Certificate of Analysis and Safety Data Sheet are available upon request.
Frequently asked questions
Lanthanum hexaboride is used as a hot cathode material in electron microscopes and similar instruments, and as a nanoparticle for infrared absorption and hard coatings in automotive, architectural, optical and solar applications.
LaB₆, or lanthanum hexaboride, is one specific compound within the broader lanthanum boride family, with a ratio of one lanthanum atom to six boron atoms.
The nanoparticles contribute to improved light management in solar cells, helping them convert more sunlight into energy.LaB₆ ink is a stable, soluble formulation of LaB₆ nanocrystals that can be applied directly through spray, dip, spin or inkjet coating and dries below 90°C. LaB₆ powder typically requires high-temperature processing methods such as CVD or PVD to form a coating.
Yes. Because the LaB₆ ink dries at temperatures below 90°C, it can be applied to flexible and heat-sensitive substrates that cannot withstand traditional high-temperature coating processes.
LaB₆ nanoparticles work at very low doses, between 10 and 100 mg per square metre, which keeps coatings thin and largely transparent.
The shielding effect of this boride comes from how its free electrons interact with infrared light. This interaction absorbs incoming infrared rays before they pass through the material, which is what gives LaB₆ nanoparticles their radiation shielding properties at very low concentrations.
LaB₆ is generally stable under normal handling conditions. As with most metal borides, prolonged exposure to water and hydrochloric acid can affect the surface of the material, which is why proper storage and handling guidelines should be followed.
No. Lanthanum hexaboride is not classified as a dangerous good.
Disclaimer
The information provided on this page is based on current knowledge and intended for general guidance. Lanthanum hexaboride should be tested in the specific application to confirm suitability, performance and compliance with regulatory requirements. While every effort has been made to ensure accuracy, Partner in Chemicals makes no representations or warranties regarding the completeness, reliability or suitability of the content. Users should verify details and consult official datasheets or regulatory guidance when making technical or industrial decisions.