Yttrium trifluoride

Composite Resins. Many composite restorative resins have incorporated fluoride into the filler particles. One commonly used material, yttrium trifluoride [13709-49-4] is incorporated as a radiopaque filler to aid in radiographic diagnosis, and is also responsible for slow release of fluoride from the composites (280). This same effect is achieved with a barium—alumina—fluoro-siUcate glass filler in composite filling and lining materials. Sodium fluoride [7681-49-4] has also been used in composites by incorporating it into the resin matrix material where it provides long-term low level release (281-283). 

Yttrium—gallium compounds, 12 353—355 Yttrium oxide, 14 650 in SiC-ceramic fabrication, 22 535 Yttrium trifluoride, 8 340 Y-TZPb... 

Structures Related to Both the Baddeleyite and Yttrium Trifluoride Structure Types 135... 

The cubic yttrium trifluoride referred to in earlier literature is apparently NaY3Fio other similar compounds include NH4H03F10 and the Er and Tm compounds. The structure of this type of compound is illustrated in Fig. 9.7. The... 

Yttrium and lanthanum are both obtained from lanthanide minerals and the method of extraction depends on the particular mineral involved. Digestions with hydrochloric acid, sulfuric acid, or caustic soda are all used to extract the mixture of metal salts. Prior to the Second World War the separation of these mixtures was effected by fractional crystallizations, sometimes numbered in their thousands. However, during the period 1940-45 the main interest in separating these elements was in order to purify and characterize them more fully. The realization that they are also major constituents of the products of nuclear fission effected a dramatic sharpening of interest in the USA. As a result, ion-exchange techniques were developed and, together with selective complexation and solvent extraction, these have now completely supplanted the older methods of separation (p. 1228). In cases where the free metals are required, reduction of the trifluorides with metallic calcium can be used. 

The preparations of rare-earth trihalides can be found in various books (2-8) and in Taylor s review (2 ). This review, however, did not include the preparation of scandium and yttrium trihalides, and only covered the preparation of the trifluorides very briefly. We have reviewed the preparation of all the trihalides (including scandium and yttrium) from Taylor s review up to June 1979 and have also included some methods and references missed by Taylor. Although we have mentioned all the methods available for the preparation of the trihalides, emphasis has been placed on the methods used since Taylor s review, and these have been referenced fully, whereas for the other methods, Taylor s review is recommended as a source of references. 

Higher coordination numbers of 8 -F 1 are adopted in the LT-YF3 type by the trifluorides of the larger ions TP+, bP+ and the smaller rare-earth ions Sm to Ln. The tysonite or LaF3 type with CN 9 + 3 is found for the trifluorides of the larger 4f and the 5f elements (see Scandium, Yttrium the Lanthanides Inorganic Coordination Chemistry). 

YF3 crystallizes in the orthorhombic system with the Pnma group. In this stmcture, each yttrium atom is coordinated by nine fluorine atoms with eight fluorine neighbors at approximately 2.3 A and another at 2.60 A [5]. The arrangement of these nine neighboring fluorine atoms around the yttrium atom is shown in Fig. 16.3. The trifluorides of all the rare-earth elements, from samarium to lutetium, are isostructural with YF3. 

A. K. Cheetham, N. Norman, The Structures of Yttrium and Bismuth Trifluorides by Neutron Diffraction, Acta Chem. Scand., A 28, 55-60 (1974). 

Spedding FH, Henderson DC (1971) High- temperature heat contents and related thermodynamic functions of seven trifluorides of the rare earths yttrium, lanthanum, praseodymium, neodymium, gadolinium, holmium, and lutetium. J Chem Phys 54 2476-2483... 

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