Colorants, rare earth oxides

The rare earth materials must go a step further and be introduced as a 99.9% to 99.995% rare earth oxide purity. It is absolutely essential that no color occurs from the absorption... 

Herring, A. P. Dean, R. W. Drobnick, J. L. "The Use of Rare Earth Oxides to Give Color or Visible Fluorescence to Soda-Lime Glasses" presented at Am. Ceramic Society 70th Annual Meeting, Chicago, 111., April 28, 1968. Reprints available from Molybdenum Corporation of America. 

Fig. 8 Stabilization of hydrous titanium oxide surface by the addition of rare-earth oxide to the support. (From Ref.. ) (View this art in color at www.dekker.com.)...

Ceric oxide, Ce02, is prepared by igniting cerium or any cerous or ceric salt of an oxy-acid. Its density depends upon the method of preparation. The color is the subject of much discussion.) We would expect a white oxide like zirconia and thoria. White oxides have been prepared, but Brauner has shown that such ceria contains impurities. As usually obtained ceria has a pale yellow color. It volatilizes without melting or decomposition at about 1900°. Besides being a weak base it shows slight evidence of faintly acidic properties. While pure ceria is insoluble in nitric or hydrochloric acids, a mixture of rare earth oxides dissolves readily... 

The use of Rare Earths oxides in the glass composition allows the manufacturing of bright and stable colored glass pieces with good thermal and chemical resistance. Choice of Rare Earth element and concentration of addition, usually ranging from 2 to 6%, is driven by final desired shade [23]. 

The cost of 99.9% erbium metal is about 21/g. Erbium is finding nuclear and metallurgical uses. Added to vanadium, for example, erbium lowers the hardness and improves workability. Most of the rare-earth oxides have sharp absorption bands in the visible, ultraviolet, and near infrared. This property, associated with the electronic structure, gives beautiful pastel colors to many of the rare-earth salts. Erbium oxide gives a pink color and has been used as a colorant in glasses and porcelain enamel glazes. 

Gr. neos, new, and didymos, twin) In 1841, Mosander, extracted from cerite a new rose-colored oxide, which he believed contained a new element. He named the element didymium, as it was an inseparable twin brother of lanthanum. In 1885 von Welsbach separated didymium into two new elemental components, neodymia and praseodymia, by repeated fractionation of ammonium didymium nitrate. While the free metal is in misch metal, long known and used as a pyrophoric alloy for light flints, the element was not isolated in relatively pure form until 1925. Neodymium is present in misch metal to the extent of about 18%. It is present in the minerals monazite and bastnasite, which are principal sources of rare-earth metals. 

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