Rare earth oxide elements yttrium group

Source Monazite, bastnasite, and related fluocarbo-nate minerals as well as minerals of the yttrium group. These ores contain varying percentages of rare-earth oxides, which are often loosely called rare earths. Rare earth elements also occur as fission products of uranium and plutonium. 

Rare Earths. Oxides of the rare earth elements of Group III in the Periodic System. Those used in ceramics are the oxides of lanthanum, cerium, PRASEODYMIUM, NEODYMIUM, and YTTRIUM (q.V.). 

Rare earth metals (REM) include 15 lanthanides elements (Ln) from atomic number 57-71 located in the IIIB group of the periodic table and scandium (Sc) and yttrium (Y) elements, as listed in Table 1. The most common oxidation state for the rare earth metal elements is RE ", but some other... 

The iota phase itself is specifically exhibited in the Ce, Pr, Tb and Cm pure binary oxides, and, in addition, oxides of this composition show a tendency for stability in the PuO and AmO. - systems. In addition, it is a very stable structure in the ternary oxides M03-3R203, where M is W, U, or Mo, and R is a rare earth element. The uranium-yttrium compound may have variable composition without phase transformation. Closely related structures having the same space group have also been prepared and characterized in the zirconia-scandia system (Zr5Sc20j3 and Zr3Sc40i2). ... 

Thus, Mosander s activities led to the originally two-element division into a six-element division. The cerium compounds are yellow at the higher oxidation level and colourless at the lower oxidation level, lanthanum compounds are white, didymium compounds are red, yttrium and erbium compounds are white, terbium compounds are pink. Chemists existed, of course, who disputed the existence of these elements. Unequivocal identification of elements was, however, possible in later times only. In the period in question, the main characteristics on the basis of which a substance could be qualified as a new element were separability, colour, crystal shape and reactivity. Even atomic mass determinations were largely uncertain, particularly in the group of the rare earth elements, it will be seen in the... 

In the comprehensive studies of the radioactive species produced in the fission of uranium it has been found that over thirty are members of the rare earth family (isotopes of yttrium and the group lanthanum through europium). The chemical and physical identification of these was an important part of the research program of the Manhattan Project. Standard oxidative separations and fractional precipitations and the use of radiochemical methods based on chain relations served to distinguish the activities of yttrium, lanthanum, cerium, and some of praseodymium, and those of samarium and europium. The characterization of the sequence praseodymium, neodymium, and element 61 presented very difficult problems that were solved only with the intensification of ion exchange methods originally developed by Boyd and co-workers and applied to the rare earth field by Cohn and co-workers. (Marinsky et al. 1947)... 

Occurrence Yttrium is a rare earth element and occurs in nearly all of the rare earth minerals. Rare earths are defined as a group of 17 elements, comprised of scandium, yttrium, and the lanthanides. The similar radii and oxidation states of the rare earths allows liberal substitution of the rare earths for one another into the crystal lattice sites of minerals. This substimtion accounts for their wide dispersion in the earth s crust and the characteristic occurrence as a group of elements within more than 100 minerals. The principal ores of the rare earths are basmasite, monazite, and xenotime. Several of the ores occur in unique geologic settings, whereas others are found in similar occurrences worldwide. 

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