For What Is Europium Used?

Europium is a rare-earth metal that has a wide variety of uses in modern technologies. This silvery-white metal readily oxidizes when exposed to air and glows a bright red color under UV light. But what exactly makes europium so useful?

An Overview of Europium

Europium is one of the rarest elements on Earth. It makes up just 0.02 parts per million of the Earth's crust. Europium belongs to the lanthanide series and has an atomic number of 63. Some key facts about europium include:

It has a melting point of 822°C and a boiling point of 1597°C.
It has a density of 5.243 g/cm3, making it about 36% denser than iron.
It reacts quickly with air, oxygen, and moisture.
Europium commonly forms compounds in the +2 and +3 oxidation states.
It has no biological role and is of moderately low toxicity to humans.

The largest deposits of europium occur in bastnasite and monazite minerals. China currently produces around 95% of the world's europium. In recent years, europium prices have ranged between $500-$1000 per kilogram.

Now that we've covered some europium basics, let's look at the main uses of this rare earth metal.

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Europium's Role in Euro Banknotes

One of the most well-known uses of europium is in Euro banknotes. Ever notice the bright red glow from a Euro bill held under a UV light? That comes from europium oxide nanoparticles incorporated into the ink.

According to a study in the journal Optical Materials, this europium-based ink helps improve the security of Euro banknotes and makes counterfeiting more difficult. The researchers found the europium luminescence was still detectable even at nanoscale concentrations as low as 0.02% by weight.

When exposed to UV light, the europium glows a vibrant red – easily distinguishable from the dull appearance of forged banknotes lacking europium. This provides cashiers and bank employees with a reliable method to screen for counterfeit euros.

Role in Fluorescent Lighting

Fluorescent lamps and bulbs rely on phosphors – compounds that exhibit luminescence when exposed to radiation – for their operation. Europium phosphors are widely used in the phosphor coatings inside fluorescent lamps and bulbs.

When ultraviolet radiation strikes a europium phosphor, it absorbs this energy and re-emits it as visible light. Special blends of europium and other rare earth phosphors allow fluorescent bulbs to produce a pleasant, natural white light.

According to the Rare Earth Technology Alliance, europium phosphors help balance the blue wavelengths emitted by fluorescent lamps with red wavelengths. This mitigates the harsh, cold-looking light that comes from lamps without europium red phosphors.

Fluorescent lamps account for around 15-20% of europium consumption today. Europium phosphors make these energy efficient bulbs possible.

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Essential for LED Screens

The next time you're watching a massive LED screen at a concert or sporting event, know that europium makes those bright, vibrant displays possible.

Europium phosphors are used in the red pixels of LED screens. A research article in Scientific Reports explains europium is unrivaled in its ability to produce narrow bandwidth red emission – an essential trait for LED screens.

The study also noted advances in europium phosphor technology have significantly improved the luminous efficiency of red phosphors over the past 25 years. Thanks to europium, today's LED screens can display a wider color gamut while using less energy.

LED screens utilize europium primarily for its role in red phosphors. But europium also assists with the blue color pixels in some LED displays.

Giving Color to TVs and Computer Monitors

Long before LED screens became popular, cathode ray tube (CRT) TV sets relied heavily on europium phosphors. These phosphors coat the inside of the CRT screen and provide red, blue, and green pixels when stimulated by electrons from the cathode ray tube.

A 2000 industry report estimated europium comprised 8-10% of the material weight of cathode ray tubes. At the time, over one metric ton of europium was consumed annually for CRT phosphors.

Although cathode ray tube TVs and monitors are now obsolete, their replacements (LCD and OLED screens) also use europium phosphors. Europium remains an essential element for television displays and computer monitors into the future.

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Improving the Performance of Nuclear Reactors

Europium has an unrivaled ability to absorb neutrons released by nuclear fission reactions. This makes europium an ideal material for control rods placed inside nuclear reactors.

Control rods regulate the fission rate inside a reactor core. When lowered further into the core, europium control rods absorb more neutrons and slow the rate of fission. Conversely, raising control rods allows more neutrons to trigger fission reactions.

According to the Jefferson Laboratory, europium's ability to absorb neutrons is 45 times greater than that of ordinary control rod materials like cadmium. The addition of just a small amount of europium greatly enhances control over nuclear reactors.

While most nuclear power plants today use alternative neutron absorbers like boron carbide, europium still plays an important role. It allows control rods to better regulate fission rates and prevent reactors from overheating.

Applications in Laser Technology

While not the most common use, europium has some intriguing applications in laser technology. Certain europium compounds, when embedded in solid-state matrixes like plastic, can harness and amplify light.

A research study in Optics Express demonstrated how europium-complex doped PMMA holds promise for solid-state dye lasers. The researchers achieved lasing action in the reddish orange region of visible light at low europium concentrations around 10^-5 M.

Other studies propose using europium to dope glass and crystal matrixes in the effort to develop new solid-state laser materials. While still an emerging application, europium shows versatility as a laser medium for visible light frequencies.

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Enabling Superconductivity

Although not its primary use, europium has a role in advanced electronics as a component of superconducting materials. Certain europium-based alloys become superconducting at cryogenic temperatures near absolute zero.

A 2011 research paper documented superconductivity in europium-lead thin films at temperatures around 1.8 K. The study found the thin europium-lead layers remained superconducting at magnetic fields up to 1 tesla in strength.

Researchers have also developed superconducting materials by combining europium, barium, copper, and oxygen into crystalline structures. These europium barium copper oxides can superconduct at temperatures between 20-40 K based on their composition.

While more exotic alloys have surpassed europium for the highest temperature superconductors, europium compounds remain of interest for specialized applications. Their superconductivity may allow electronics to operate at higher efficiency in the future.

A Versatile Component of Phosphor Blends

Much of europium's utility stems from its use in phosphor blends for lighting, display screens, and detectors. In addition to the applications outlined above, europium also appears in:

X-ray phosphors that capture images on radiographic films. Europium improves the sensitivity of these screens.
Radioluminescent paints containing europium can glow brightly for hours after exposure to radiation. This allows radiation doses to be measured visually.
Plastic scintillators embedded with europium salicylate make efficient detectors for high-energy elementary particles.
Photo-luminescent tags on products that glow red under UV light. These verify authenticity.

Researchers also continue investigating new phosphor formulations with europium. From bioimaging to solar cells to radiation detection, europium's phosphorescence has many untapped uses.

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Health Effects and Environmental Considerations

In terms of health impacts, europium is generally considered non-toxic with low risk to humans. That said, exposure to europium compounds may cause some skin and eye irritation. Like other heavy metals, europium can also accumulate in bones if ingested over a long period.

The environmental impact from europium is relatively small compared to mining of other rare earth elements. Only minimal amounts of europium are required for most applications, so extraction is limited. However, toxic acids are still used to leach europium from mined ores, which carries environmental risks if not managed properly.

As a whole, the unique properties of europium make it difficult to replace in key technologies like LED displays, fluorescent lamps, and lasers. Despite its rarity, europium will likely remain an essential specialty metal into the future with few substitutes.

Conclusion

While it may not be a household name, europium is a vital mineral that helps power modern life. Europium provides crucial red phosphors for lighting applications and enables vibrant color displays in TV, computer, and phone screens. It also has specialized uses in nuclear reactor control, lasers, and superconductors – along with anti-counterfeiting protection in Euro banknotes.

In the future, researchers will likely discover even more uses for europium's unusual properties like its ability to absorb neutrons and emit pure red wavelengths under UV stimulation. Even as technologies change, this rare earth element will continue lighting up our world.

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