Melting point rare earth elements

Scandium is a soft, lightweight, silvery-white metal that does not tarnish in air, but over time, it turns yellowish-pink. It resists corrosion. Scandium reacts vigorously with acids, but not water. Scandium has some properties similar to the rare-earth elements. Although its position in group 3 places it at the head of the 17 elements of the lanthanide series of rare-earth metals, scandium, as a metal, is not usually considered a rare-earth. Scandiums melting point is l,54l°C, its boiling point is 2836°C, and its density is 2.989 glctn . 

Samarium is a yellowish metal with a melting point of 1,962°F (1,072°C) and a boiling point of about 3,450°F (1,900°C). Its density is 7.53 grams per cubic centimeter. Samarium is the hardest and most brittle of the rare earth elements. 

Our experiments (Table 2) show that the enthalpy of formation does indeed decrease with ascending atomic number of the rare-earth element. The variation of along the rare-earth sulfide series is correlated with the values of the melting points of Ln8 and Ln2 and of the activation energy of carriers in the intrinsic conduction region of 1 1283. 

From the IIIB (B, Al, Ga, In, Tl) through VIB (O, S, Se, Te, Po) the melting points for at least one or two or even three of the compounds are much higher (several hundreds to more than one thousand ""C) than that of the highest melting component element (generally the rare earth element). Boron and carbon, of course. 

A rather interesting plot (see fig. 9.6a) is the initial melting slope dT/dP of the rare earth elements versus atomic number. In this plot the divalent and trivalent lines are well established from the slopes of Eu and Yb and from La, Gd and Lu respectively. The quadrivalent line drawn parallel to these is perhaps not unreasonable. The deviations of the data points from the trivalent line, of Sm... 

Rare-earth fluorides exist either as hexagonal (Lap3) or as orthorhombic structures ((3-YP3), as shown in fig. 17 for rare-earth fluorides with La to Lu (Thomas and Brunton 1966). Pluorides of the rare-earth elements La to Nd crystallize in the tysonite structure at all temperature ranges below the melting point. Smp3 to Gdp3 are orthorhombic at lower... 

TABLE VII Melting Points, Boiling Points, and Crystal Structures and Volume of the Rare Earth Elements... 

Vapour pressures, melting points and refinement techniques for rare earth elements. 

With Au, the stoichiometry of the compound which exhibits the highest melting point is RAu for the majority of the rare earth elements, and it is AuTh2, AU2U and AusPu for the actinides. 

As a part of the Introduction a list of the important properties of the pure rare earth elements, as pertaining to phase equilibria are presented. These data are included here since a wide variation of melting point and transition point data exists in the literature. The phase relationships that follow will be standardized to these data. 

Table 1 shows some of the physical properties of the more common rare earth elements and, for comparison, those of reactive metals and iron (Beaudry and Gschneidner 1978, Grayson 1985, Bingel and Scott 1973). Figure 1 shows the temperature dependence of the vapor pressure of these elements (Barin 1989). The melting points and vapor pressures of rare earths differ from those of iron to such an extent that problems of dissolution... 

The melting points and densities of these compounds for the major rare earth elements are high as shown in table 4 (Bingel and Scott 1973). The best known element of this series is cerium, and the melting point of its sulfide, CeS, is about 2450°C. Owing to their high density, however, removal by floatation will be not easy in some cases. 

---