Rare earths lanthanides

Apatite and other phosphorites constitute a substantial resource of rare earths. The REO content is highly variable and ranges from trace amounts to over 1%. Apatite- [1306-05-4] rich tailings of the iron ore at Mineville, New York, have been considered a potential source of yttrium and lanthanides. Rare-earth-rich apatites are found at the Kola Peninsula, Russia, and the Phalaborwa complex in South Africa. In spite of low REO content apatites could become an important source of rare earths because these are processed in large quantities for the manufacturing of fertilisers (qv). 

Schumm, R. H. Wagman, D. D. Bailey, S. Evans, W. H. Parker, V. B. "Selected Values of Thermodynamic Properties. Table for the Lanthanide (Rare Earth) Elements (Elements 62 through 76 in the Standard Order of Arrangement)" Nat. Bur. Stand. Tech. Note No. 270-7, April 1973. 

Figure 6.1 An energy-level diagram for trivalent lanthanide rare earth ions in lanthanum chloride (after Dieke, 1968).

Suppose that you are going to develop an ultraviolet-emitting phosphor based on a trivalent lanthanide rare earth ion doped crystal. If you want this phosphor... 

Yttrium is always found with the rare-earth elements, and in some ways it resembles them. Although it is sometimes classified as a rare-earth element, it is listed in the periodic table as the first element in the second row (period 5) of the transition metals. It is thus also classified as the lightest in atomic weight of all the rare-earths. (Note Yttrium is located in the periodic table just above the element lanthanum (group 3), which begins the lanthanide rare-earth series. 

Promethium was the missing element in the lanthanide rare-earth series in the periodic table. Since it does not exist on Earth, it was not recovered until nuclear reactors were common. Even so, scientists found it difficult to isolate it from other rare-earths. 

Figure 8.1 Periodic system, 1920s and 1930s. Prior to the 1940s, the lanthanides (rare-earths) were grouped separately as shown, but Th, Pa, and U (now classified as actinides), were considered to be transition elements, as shown in this table according to A. von Antropoff. From J. W. van Spronsen, The Periodic System of the Chemical Elements A History of the First Hundred Years (Amsterdam, 1969), fig. 59, p. 160.

Oxides of the lanthanide rare earth elements share some of the properties of transition-metal oxides, at least for cations that can have two stable valence states. (None of the lanthanide rare earth cations have more than two ionic valence states.) Oxides of those elements that can only have a single ionic valence are subject to the limitations imposed on similar non-transition-metal oxides. One actinide rare-earth oxide, UO2, has understandably received quite a bit of attention from surface scientists [1]. Since U can exist in four non-zero valence states, UO2 behaves more like the transition-metal oxides. The electronic properties of rare-earth oxides differ from those of transition-metal oxides, however, because of the presence of partially filled f-electron shells, where the f-electrons are spatially more highly localized than are d-electrons. 

Gd and Eu (4 ) can also be used as broadening probes. Trivalent lanthanide (rare earth) ions, like Ca (which is also of a similar size) bind... 

On the other hand, if a TM metal atom wi h formal ionic valence of more than 4, e.g., V, Cr, Mn, Fe, Co, Ni or Cu from the first row TM atoms, is an intentionally added impurity or alloy atom, and if this atom is resident on a group IV atom site that is fully-bonded to O, then additional occupied d-states can either be incorporated into the otherwise forbidden band gap between the occupied valence band states, and the empty conduction band states of the group IVB host and give rise to excited bound resonance states within the vacuum continuum. Additionally, if the TM d-states are more than half-occupied for a relevant ionic state, then occupied d-states associated with occupancy beyond five d-states sometimes drop into the valence band and are therefore present as bound state resonances [1]. The same description applies to 4f states in the lanthanide rare earth series. At the beginning of the series, there are occupied 4f states above the valence band edge. Later en the series, beyond Gd, a portion of these states drop into the valence band. By the time the third row of transition atoms begins, for example for Hf, the occupied 4f states are below the valence band. 

Heterogeneous fluorescent immunoassays for T4 based on lanthanide rare earth ions and time-resolved fluorescence were also developed. The use of europium chelates as fluorescent probes is particularly attractive because of their extraordinarily long Stokes shifts and long fluorescence decay times. Thus the sharp emission peak of europium (613 nm) can be easily separated fr om scattering caused by excitation light (340 nm) or by interfering substances in... 

The revised Periodic Table, then, listed the heaviest elements as a second rare earth series, and these heaviest elements—for which the name actinide elements was then suggested—were paired off with elements in the already-known lanthanide rare earth series. 

Because the lanthanides ("rare earths") have become prominent in the manufacture of fluorescent lamps, we will address this technology next to show how they differ from the Sq activators given above. We will find that these cations can be used in situations where no other activators can be applied. 

The lanthanides (rare earths) have found use in regard to phosphors, solid state lasers (which are specialized phosphors) and Anti-Stokes phosphors. Indeed, if rare earths were not available, we would not have useful lasers,... 

As early as 1923 N. Bohr suggested that there might exist a group of IS elements at the end of the Periodic Table Uiat would be analogous in their properties to the IS lanthanide ("rare earth") elemrats. This idea, combined with the increasing stability of the -t-3 oxidation state for the transuranium elem ts as the atomic number increases from Z = 93 to 96, led Seaborg to the conclusion that these new elemrats constituted a second rare earth series whose initial member was actinium. As the atomic number increases from 90, electrons are added in the Sf subshell similar to the occupation of the 4f subshell in the lanthanides, see Table 16.1. This series would be terminated with element 103 since this would correspond to the addition of 14 electrons for a completed Sf subshell. 

There remained one last truant element 61, a member of the lanthanides ( rare earths ) that had confused great chemists for more than a century (chapter 1). In 1945, Jacob Marinsky (1918- ) and Larry Glendenin (1918- ), working with Charles D. Coryell (1912-71) at Oak... 

Table SI. 3 The electronic configurations of the lanthanides (rare earth elements) and their ions...

The dominant single crystal for solid-state lasers is YAG, which is produced using the Cz melt-growth process [29]. Transition metal elements or lanthanide rare earth elements are used as laser active ions that are doped in YAG host material. Due to its narrow spectral width and high quantum efficiency, Nd ion, a four-level laser system has been acknowledged to be the most popular active ion. 

Strontium and lanthanides (rare earths), found in igneous rocks, inhibit rehydration of the hemihy-drate to gypsum, which can cause problems in certain phosphoric acid processes. Moreover strontium causes problems in the concentration sections because strontium sulfate has a minimum solubility in 40% P2O5 acid. An extremely thin film of SrS04 causes a very pronounced reduction in the capacity of the concentration unit. 

Aufbau principle, p. 307 Emission spectra, p. 282 Lanthanide (rare earth) Photon, p. 280... 

---