Lanthanum - Applications

Applications

The first historical application of lanthanum was in gas lantern mantles. Carl Auer von Welsbach used a mixture of 60% magnesium oxide, 20% lanthanum oxide and 20% yttrium oxide which he called Actinophor, and patented in 1885. The original mantles gave a green-tinted light and were not very successful, and his first company, which established a factory in Atzgersdorf in 1887, failed in 1889.

Modern uses of lanthanum include:

• One material used for anodic material of nickel-metal hydride batteries is La(Ni_3.6Mn_0.4Al_0.3Co_0.7. Due to high cost to extract the other lanthanides a mischmetal with more than 50% of lanthanum is used instead of pure lanthanum. The compound is an intermetallic component of the AB₅ type.

As most hybrid cars use nickel-metal hydride batteries, massive quantities of lanthanum are required for the production of hybrid automobiles. A typical hybrid automobile battery for a Toyota Prius requires 10 to 15 kg (22-33 lb) of lanthanum. As engineers push the technology to increase fuel mileage, twice that amount of lanthanum could be required per vehicle.

• Hydrogen sponge alloys can contain lanthanum. These alloys are capable of storing up to 400 times their own volume of hydrogen gas in a reversible adsorption process. Heat energy is released every time they do so; therefore these alloys have possibilities in energy conservation systems.
• Mischmetal, a pyrophoric alloy used in lighter flints, contains 25% to 45% lanthanum.
• Lanthanum oxide and the boride are used in electronic vacuum tubes as hot cathode materials with strong emissivity of electrons. Crystals of LaB₆ are used in high brightness, extended life, thermionic electron emission sources for electron microscopes and Hall effect thrusters.
• Lanthanum fluoride (LaF₃) is an essential component of a heavy fluoride glass named ZBLAN. This glass has superior transmittance in the infrared range and is therefore used for fiber-optical communication systems.
• Cerium doped lanthanum bromide and lanthanum chloride are the recent inorganic scintillators which have a combination of high light yield, best energy resolution and fast response. Their high yield converts into superior energy resolution; moreover, the light output is very stable and quite high over a very wide range of temperatures, making it particularly attractive for high temperature applications. These scintillators are already widely used commercially in detectors of neutrons or gamma rays.
• Carbon arc lamps use a mixture of rare earth elements to improve the light quality. This application, especially by the motion picture industry for studio lighting and projection, consumed about 25% of the rare-earth compounds produced until the phase out of Carbon arc lamps.
• Lanthanum(III) oxide (La₂O₃) improves the alkali resistance of glass, and is used in making special optical glasses, such as infrared-absorbing glass, as well as camera and telescope lenses, because of the high refractive index and low dispersion of rare-earth glasses. Lanthanum oxide is also used as a grain growth additive during the liquid phase sintering of silicon nitride and zirconium diboride.
• Small amounts of lanthanum added to steel improves its malleability, resistance to impact and ductility. Whereas addition of lanthanum to molybdenum decreases its hardness and sensitivity to temperature variations.
• Small amounts of lanthanum are present in many pool products to remove the phosphates that feed algae.
• Lanthanum oxide additive to tungsten is used in gas tungsten arc welding electrodes, as a substitute for radioactive thorium.
• Various compounds of lanthanum and other rare-earth elements (oxides, chlorides, etc.) are components of various catalysis, such as petroleum cracking catalysts.
• Lanthanum-barium radiometric dating is used to estimate age of rocks and ores, though the technique has limited popularity.
• Lanthanum carbonate was approved as a medication (Fosrenol, Shire Pharmaceuticals) to absorb excess phosphate in cases of end-stage renal failure.
• Lanthanum fluoride is used in phosphor lamp coatings. Mixed with europium fluoride, it is also applied in the crystal membrane of fluoride ion-selective electrodes.
• Like horseradish peroxidase, lanthanum is used as an electron-dense tracer in molecular biology.