Rundown about Erbium

As a silvery white rare earth metal, erbium is an element from lanthanides group of the periodic table with the atomic mass of 167.2 u and the atomic number of 68. Erbium occurs naturally as salts or other chemicals and found mostly in a mineral called gadolinite and bound in monazite sand ores. The amount of erbium is almost very low on Earth crust as 2.8 mg/Kg and around 0.9 nanogram in one litter of sea water. However, this very low abundance ranks it the 45^th among the most abundant elements on Earth. Since the appearance of ion exchange chromatography, it has been quite easy to separate rare earth metals from each other. Nevertheless, it was too costly to achieve them isolated and separated. Therefore, the development of separations methods has driven down the price of erbium and other rare earth metals with an adequate amount of annual production. The main sources of erbium for commercial purposes are euxenite and xenotime. If erbium is digested in human body, it can cause a slight toxicity but in general, this rare metal and its compounds aren’t toxic at all. So far, no clear biological function has been found for erbium in human body but it should be mentioned that human bones have most erbium compared to other organs.

Physical and Chemical Properties

Erbium is a malleable metal and therefore, it is shaped easily while it’s stable in the atmospheric conditions and isn’t oxidized like the other rare earth metals. In the electromagnetic infrared, ultraviolet and visible regions, erbium had sharp absorption spectra, whereas in the other regions, this metal seems like the other rare metals too. As it was mentioned before, erbium occurs as salts like erbia which is a trivalent salt (sesquioxide). As a known compound of erbium, Er₃N is a group of propeller-like atomic clusters with erbium atoms located 3.5 picometers from each other. Encapsulating can isolate these clusters in the Er₃N to form fullerenes. Erbium has six naturally stable isotopes among which 166Erbium is regarded as the most common one. There are twenty nine radioisotopes of erbium. This rare metal burns gradually burns when its exposed to the air forming the oxidized form erbium (III) oxide. Erbium is quite electropositive and reacts with cold water slowly and a bit faster with hot water to form erbium hydroxide.

Erbium Production

To begin with, the minerals that contain erbium salts and compounds are finely crushed and then poured in hydrochloric or sulfuric acids in order to dissolve the insoluble rare earth metals oxides soluble. Next, the pH of the mixture is risen to be around 3 or 4 by sodium hydroxide (NaOH) so that the acidic filtrates get neutralized. As a result of the change in the pH, thorium (a metal from actinides family) precipitates. Later, ammonium oxalate is added to the solution to form the insoluble earth metals oxalates with subsequent conversion of them to their oxides through annealing. After that, the obtained oxides get dissolved in nitric acid (HNO₃) in order to remove cerium (a lanthanide family metal). Next, magnesium nitrate is added to the solution to create a mixture of rare earth metals double salts with a consecutive separation using ion exchange technique. Then, the rare metal ions are adsorbed on the surface of some particular resin through exchanging ammonium or hydrogen. Finally, the rare earth metals ions are washed with complexing agents to get separated selectively. At this step, erbium is achieved through heating up at 1450˚C under argon atmosphere along with calcium.

Click Images to Check Our Other Article On Blografi

Erbium Applications

The major applications of erbium are in optics with the pink erbium cation (Er³⁺) with fluorescent properties specifically used in laser. Glasses or crystals that are coated with erbium (erbium-doped compounds) are employed in optical amplification media by optical excitation of erbium cation at the wavelength of 980 to 1480 nm with subsequent emission radiation of light a 1530 nm. This excitation/emission process amplifies laser simply and mechanically and is used for signals that are transmitted by fiber optics. In optical communications, the wavelength of 1550 nm is critical since there is the least amount of standard single mode optical fibers loss is gained at that region. These properties bring about a lot of applications for erbium in optics such as organo-erbium systems for optical amplification at telecommunications wavelengths ¹, optical frequency synthesizer with an integrated erbium tunable laser ², giant optical gain in a single-crystal erbium chloride silicate nanowire ³ and silicon photonic Data Link with a Monolithic erbium-Doped Laser ⁴.

There is a fact that today’s modern technology greatly depends on transmitting and manipulating optical signals. Amplification in optics has a vital role mainly because all the involving components in a practical communication system generate loss. There are two main problems with the current amplifiers which totally depend on erbium ions. The first one is the problem with integrating on a given substrate and other is the necessity of having power with high densities. Through using an integrated organo-erbium system, the above-mentioned problems can be solved ¹. The need for faster and better communication in the modern life today requires wider bandwidths which is now possible by employing silicon photonic data links equipped with monolithic erbium-doped laser ⁴. Regarding the substantial application of erbium in optics and laser, erbium has found numerous applications in medicine namely dermatology and dentistry which closely depend on the emission of erbium ions at the wavelength 2940 nm with applications in laser surgery. An alloy made of erbium and vanadium causes a decrease in the hardness with advantages in metallurgy. Another alloy made of erbium and nickel (Er₃Ni) has really high specific heat capacity and is used in cooling equipment.

Erbium has a major application in optics, laser and amplifiers. The modern time communication technology needs erbium-doped optical devices for a faster data transmit with wider bandwidth. Erbium is applied as erbium-doped optical silica-glass, Optical frequency synthesizers, optical communications, fiber lasers and erbium-doped waveguide amplifiers. Erbium-based non-semiconductor techniques are truly advantageous as erbium-doped waveguide amplifiers have shown to modulate transfer speed of 170 gigabyte per second ³. There have been various medical applications for erbium in medicine. Erbium has broad bandwidth enabling wide tunability throughout different wavelengths in electromagnetic region. Erbium-based materials are preferred to semiconductors in systems with quantum information at the wavelengths that are mainly for telecommunication because of the sharp spectral features in erbium than in semiconductors as well as the longer quantum coherence lifetimes.

References

1. Ye, H. Q. et al. Organo-erbium systems for optical amplification at telecommunications wavelengths. Nat. Mater. 13, 382–386 (2014).

2. Xin, M. et al. Optical frequency synthesizer with an integrated erbium tunable laser. Light Sci. Appl. 8, (2019).

3. Sun, H. et al. Giant optical gain in a single-crystal erbium chloride silicate nanowire. Nat. Photonics 11, 589–593 (2017).

4. Li, N. et al. A Silicon Photonic Data Link with a Monolithic Erbium-Doped Laser. Sci. Rep. 10, 1–9 (2020).