Niobium is a chemical element that is a soft, gray, ductile transition metal, often found in pyrochlore and columbite minerals. Its name comes from Greek mythology, especially Niobe, who was the daughter of Tantalus, the namesake of tantalum. The name reflects the great similarity between the two elements in their physical and chemical properties, which makes them difficult to distinguish.
Lithium niobate, which is a ferroelectric, is widely used in mobile phones and optical modulators, and for the manufacture of surface acoustic wave devices. It belongs to the ABO3 structure of ferroelectrics such as lithium tantalate and barium titanate. Niobium capacitors are available as an alternative to tantalum capacitors, but tantalum capacitors still predominate. The niobium is added to the glass to obtain a higher refractive index, which makes possible finer and lighter corrective lenses.
Niobium sheet is used as a precious metal in commemorative coins, often in silver or gold. For example, Austria produced a series of niobium silver coins from 2003; the color of these pieces is created by the diffraction of light by a thin layer of anodized oxide. In 2012, ten coins show a wide variety of colors in the center of the room: blue, green, brown, purple, purple or yellow. Two other examples are the Austrian commemorative coin of the Austrian alpine railways of 25 years and 150 euros and the Austrian commemorative coin 2006 of 25 euros. In 2004, the Royal Canadian Mint began production of a $ 5 silver and niobium coin named Hunter's Moon, in which niobium was selectively oxidized, thus creating unique finishes where no two pieces are exactly alike.
The arc tube joints of high-pressure sodium lamps are made from niobium powder, sometimes alloyed with 1% zirconium; Niobium has a very similar thermal expansion coefficient, corresponding to sintered alumina arc tube ceramic, a translucent material that is resistant to chemical attack or reduction by the hot liquid of sodium and sodium vapor contained in the operating lamp.