Applications of the Rare Earths

Many technological items that people are familiar with in modern society depend critically on the rare earths. But these elements are used also in other applications that people do not see directly. The number of applications discussed is large, but not exhaustive in keeping with the preferred brevity and conciseness of volumes in the series in which this book appears. 

The applications may be very high tech, but not necessarily. Examples of the latter are for instance pigments or the alloy called misch metal (see Sect. 5.5). 

In Table 5.1. you will find the most important applications for a number of 

---

The industrial applications of the rare earths can be divided into two categories— uses that involve the mixed rare earths in proportion to their occurrence in their ores or in concentrates (not exceeding 90% of any one rare earth element), and uses that involve the separated individual rare earth elements (> 90% pure). Of the total volume of rare earths consumed about 95% is in the form of mixed rare earths or concentrates, but in monetary terms the contribution by both categories is about equal. 

Fran 1960 to the present is the time of qualitatively and quantitatively rapidly rising applications of the rare earth elements ghich are new abundantly available in every desired quality, although not alvnays at a low price. 

So it was at the beginning of the industrial applications of the rare earth elements the need of the rare earth industry to utilize valuable residual fractions. Up to the present day, this remains a problem to be solved by research departments, applications technicians, inventors and developers of the rare earth industry. 

The first applications of the rare earth elements / as already mentioned, were in the optical field, namely the Auer incandescent mantles and the arc light carbons. In 1964/65 as a result of the work of Levine and Palilla the use of the truly rare and therefore expensive europium together with yttrium made a major leap forward for the rare earth industry as red phosfdiors in color TV screens. Due to the strong and sharp emission line of europium at 610 A, without a yellow component, viiich is... 

In the large scale application of rare earth elenents as in the steel industry, in catalysts and in the polishing of glass, in general, the naturally occurring mixtures or concentrates are utilized. While with phosphors and electronic applications pure products with much higher prices are used. Therefore, the application of the rare earth elements requires careful consideration and close cooperation between producers and users so that the optimum between desired effects, purity and production costs can be found for each specific application. 

The oonsunption of the rare earth elements is divided into four groups of application (2). One can see from this information that 98 % of the rare earth elements, with respect to quantity, are consumed in the following fields of application metallurgy, chemicals/catalysts, glass and polishing media. If one however looks at the value of the prodiacts then the picture is drastically altered, then phosphors are the most inportant field of application of the rare earth elements. 

Linebarger H. F. et ai. The Role of the Rare Earth Elements in the Production of Nodular Iron, in Am.Chem.Soc. Symposium series 164, "Industrial Applications of the Rare Earths" ed. Gschneidner K. A., publ. 1981, 20... 

For a better understanding of many successful applications of the rare earth-alkali metal containing LnM3tris (binaphthoxide) complexes (LnMB, Ln=rare earth, M=alkali metal) to catalytic asymmetric synthesis, intense investigations also focused on the determination of the structure. It has been shown that these complexes, which can be readily prepared from the corresponding rare earth trichlorides and/or rare earth isopropoxides [5],possess a structure as presented in Fig. 2. This structure was supported by various NMR spectroscopic, MS spectrometric, X-ray crystallographic and other analytic investigations of a variety of LnMB complexes. 

Chapters devoted primarily to catalysis have been published in earlier volumes of the Handbook. Note especially chapter 43 on absorption and catalysis on surfaces, chapter 57 on catalysis in organic synthesis, and chapter 61 on coordination catalysts. In this volume we add several chapters that will continue our coverage of these important applications of the rare earths. 

We have now investigated further the importance of the modification of the zeolite on its activity in catalysing the acylation reaction. Of particular interest was the application of the rare-earth (RE) exchanged zeolites to acylation reactions using acid chlorides. Previous studies had either tested the RE modified zeolite systems with the carboxylic acid [3,4] or applied only the H-form of the zeolite to the acid chloride system [5-7]. We were interested in the role of the rare-earth cation in enhancing the activity of the catalyst with the acid chloride. 

In the case of the disposal of high-level light water reactor waste, these wastes intrinsically contain up to 35 wt % rare-earth oxides that could be directly converted to form part of the monazite host matrix. Because Ewing and Wang (this volume) have provided a comparison of the properties of monazite-based waste forms to those of other crystalline host media and nuclear waste phosphate glasses, no further details regarding this application of the rare-earth orthophosphates will be given here. 

The last half of the book has given a space to thermochemistry, trace determination, and applications of the rare earth oxides, as well as single crystal growth and fine particle preparation. From a practical aspect, synthesis and application of the nanoparticles is going to exploit new application areas in a broad range from traditional ceramics to some biological processes, which could not be addressed previously with the use of conventional large particles. 

First major metallurgical application of the rare earths mischmetal-iron lighter flints... 

Irritation of the conjunctiva but not to the iris and cornea are seen after topical application of the rare earths. The conjunctival ulcers produced by either rare earth crystals or strong solutions require one to three weeks for healing (Haley, 1965). Several hours or days after denudation of the cornea, an opacification of obscure mechanism occurs. This effect is produced by excess deposition of the calcium in the injured area (Haley, 1965). 

The main focus of research on the rare earth silicates has been their preparation and structure. A summary of the structural data available is presented in table 14. In many cases the physical properties are unknown. An important application of the rare earth silicates is the use of yttrium oxyorthosilicate activated with terbium as a luminescent material in fluorescent lamps. Several patents have been published in this field. 

Prochovnick, A., 1958, Metallurgical applications of the rare earths, Davison Chemical Co. Report. Puzyrev, A.V, D.Ya. Povolotskii, A.I. Strogamov and M.A. Ryss, 1970, Izv. Vyssh. Uchebn. Zaved. Chem. Metall. 13, 14. 

---