source：AZoM
Applications of Rare Earth Elements
Established industries, such as catalysts, glassmaking, lighting, and metallurgy, have been using rare earth elements for a long time. Such industries, when combined, account for 59% of the total worldwide consumption. Now newer, high-growth areas, such as battery alloys, ceramics, and permanent magnets, are also making use of rare earth elements, which accounts for the other 41%.
Rare Earth Elements in Glass Production
In the field of glass production, rare earth oxides have long been studied. More specifically, how the properties of the glass may change with the addition of these compounds. A German scientist named Drossbach began this work in the 1800s when he patented and manufactured a mixture of rare earth oxides for decolorizing glass.
Albeit in a crude form with other rare earth oxides, this was the first commercial use of cerium. Cerium was shown to be excellent for ultraviolet absorption without giving color in 1912 by Crookes of England. This makes it very useful for protective eyeglasses.
Erbium, ytterbium, and neodymium are the most widely used REEs in glass. Optical communication uses erbium-doped silica fiber extensively; engineering materials processing uses ytterbium-doped silica fiber, and glass lasers used for inertial confinement fusion apply neodymium-doped. The ability to change the fluorescent properties of the glass is one of the most important uses of REO in glass.
Fluorescent Properties from Rare Earth Oxides
Unique in the way that it can appear ordinary under visible light and can emit vivid colors when excited by certain wavelengths, fluorescent glass has many applications from medical imaging and biomedical research, to testing media, tracing and art glass enamels.
The fluorescence can persist using REOs directly incorporated into the glass matrix during melting. Other glass materials with only a fluorescent coating often fail.
During manufacturing, the introduction of rare earth ions in the structure results in optical glass fluorescence. The REE’s electrons are raised to an excited state when an incoming energy source is used to excite these active ions directly. Light emission of longer wavelength and lower energy returns the excited state to the ground state.
In industrial processes, this is particularly useful as it allows inorganic glass microspheres to be inserted into a batch to identify the manufacturer and lot number for numerous product types.
The transport of the product is not affected by the microspheres, but a particular color of light is produced when ultraviolet light is shone on the batch, which allows precise provenance of the material to be determined. This is possible with all manner of materials, including powders, plastics, papers, and liquids.
An enormous variety is provided in the microspheres by altering the number of parameters, such as the precise ratio of various REO, particle size, particle size distribution, chemical composition, fluorescent properties, color, magnetic properties, and radioactivity.
It is also advantageous to produce fluorescent microspheres from glass as they can be doped to varying degrees with REO’s, withstand high temperatures, high stresses, and are chemically inert. In comparison to polymers, they are superior in all of these areas, which allows them to be used in much lower concentrations in the products.
The relatively low solubility of REO in silica glass is one potential limitation as this may lead to the formation of rare earth clusters, particularly if the doping concentration is greater than the equilibrium solubility, and requires special action to suppress the formation of clusters.