Terbium

Accepted data have only been reported for the first hydrolysis constant of terbium by Klungness and Byrne (2000) and Frolova, Kumok and Serebrennikov (1966). These data are listed in Table 8.39. As they did with the other lanthanides, Klungness and Byrne measured the stability of TbOH across the temperature range from 25 to 55 °C and in 0.1 and 0.7 mol 1 NaClO. Frolova et al. measured the stabihty at 25 °C and in 0.3 mol 1 NaClO. The results from the two studies are in reasonable agreement. 

There is only a single literature source that lists data for the stability of the higher monomeric stability constants of terbium (Fatin-Rouge and Biinzli, 1999), where values were proposed for the stability of Tb(OH)3(aq) in two media at 0.1 mol 1 . Again, these data are not consistent with the stability constant selected for TbOH in this review. In both cases, the stability constant given for log 3 indicates that it is greater than 3-log As indicated previously, this behaviour is considered unlikely, and consequently, neither of the values is retained by this review (the values have not been listed). 

There have been no reported stability constants for polymeric hydrolysis species of terbium. 

SYMBOL Tb PERIOD 6 SERIES NAME Lanthanide ATOMIC NO 65 

ATOMIC MASS 158.925 amu VALENCE 3 and 4 OXIDATION STATE -1-3 NATURAL STATE Solid 

ISOTOPES There are a total of 52 isotopes of terbium, and only one of these is stable (Tb-159). Terbium-59 makes up 100% of the element found in the Earth s crust 

There are two allotropic (crystal forms) of terbium, both of which are dependent on its temperature. The alpha ((a) form exists at room temperatures and up to temperamres of 1,298°C, and the beta ( 3) form exists beyond these temperamres. Although terbium is a silvery metal that resembles aluminum and feels hke lead, it is much heavier than either of these two elements. It is placed in the yttrium subgroup (lanthanide series) of the rare-earths. It is also resistant to corrosion. 

Terbium is not found in great quantities on Earth. In fact, minerals where terbium is found contain about 0.03% terbium. Not much of the stable isotope is found as a free metal rather most of it is mixed with other rare-earths or are in compound forms. 

TABLE 6. Calculated values of energy differences, intramolecular energy transfer rates and theoretical and experimental quantum yields of Eu +, 6-diketonate complexes 

6-diketonate complex Transition AE (cm ) Transfer rate (s- ) theo (%) exp (%) Reference 

FIGURE 8. Emission spectmm (a) and energy level diagram (b) of epoxy 10% Tb(acac)3. Reproduced with permission from Reference 92, Copyright 2004 John Wiley Sons, Ltd 

The energy transfer from Tb + to Eu + ion in the [Eu/Tb(tfa)3(tppo)2] pure chelate and the in situ chelate doped in gel glass indicates that the Dexter exchange mechanism is operative in the energy transfer process between ions . Pettinari and coworkers showed terbium 4-acylpyrazol-5-onate and its derivatives are luminescent materials, also pointing to the importance of properties such as hydrophobicity, solubility in non-polar solvents and large size of the molecule. 

A novel bis-/3-diketone 2,6-bis(3-phenyl-3-ketopropionyl)pyridine with Eu, Tb, Sm and Gd ions is luminescent. All these rare-earth ions could be sensitized to some extent by the ligand. In particular, the Tb + complex is an excellent green emitter and may find application in organic light-emitting devices (OLEDs) and medical diagnosis . 

James G. (1973). Present Status of Drags as Teratogens in Man. Teratology International Journal of Abnormal Development 7 3-15. 

Tb compounds and complexes in most cases exhibit strong luminescence in the green portion of visible light. Ternary compounds such as 

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Ytterby, a village in Sweden near Vauxholm) Yttria, which is an earth containing yttrium, was discovered by Gadolin in 1794. Ytterby is the site of a quarry which yielded many unusual minerals containing rare earths and other elements. This small town, near Stockholm, bears the honor of giving names to erbium, terbium, and ytterbium as well as yttrium. 

Ytterby, a village in Sweden) Discovered by Mosander in 1843. Terbium is a member of the lanthanide or "rare earth" group of elements. It is found in cerite, gadolinite, and other minerals along with other rare earths. It is recovered commercially from monazite in which it is present to the extent of 0.03%, from xenotime, and from euxenite, a complex oxide containing 1% or more of terbia. 

Terbium has been isolated only in recent years with the development of ion-exchange techniques for separating the rare-earth elements. As with other rare earths, it can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible. Calcium and tantalum impurities can be removed by vacuum remelting. Other methods of isolation are possible. 

Terbium is reasonably stable in air. It is a silver-gray metal, and is malleable, ductile, and soft enough to be cut with a knife. Two crystal modifications exist, with a transformation temperature of 1289oC. Twenty one isotopes with atomic masses ranging from 145 to 165 are recognized. The oxide is a chocolate or dark maroon color. 

Sodium terbium borate is used in solid-state devices. The oxide has potential application as an activator for green phosphors used in color TV tubes. It can be used with Zr02 as a crystal stabilizer of fuel cells which operate at elevated temperature. Few other uses have been found. 

Little is known of the toxicity of terbium. It should be handled with care as with other lanthanide elements. 

Although rare-earth ions are mosdy trivalent, lanthanides can exist in the divalent or tetravalent state when the electronic configuration is close to the stable empty, half-fUed, or completely fiUed sheUs. Thus samarium, europium, thuUum, and ytterbium can exist as divalent cations in certain environments. On the other hand, tetravalent cerium, praseodymium, and terbium are found, even as oxides where trivalent and tetravalent states often coexist. The stabili2ation of the different valence states for particular rare earths is sometimes used for separation from the other trivalent lanthanides. The chemicals properties of the di- and tetravalent ions are significantly different. 

Parameter Gadolinium Terbium Dysprosium Holmium Erbium ThuUmn Ytterbium Lutetium... 

The uranium ore from Elliot Lake, Canada, contains yttrium and lanthanides (see Uranium and uranium compounds). In the Jiangxi province of the People s Repubhc of China a large reserve of a rare-earth-containing clay contains over 1,000,000 t of REO. This ore is characterized by having a low cerium content (<5%) but a high content in samarium, europium, terbium, and yttrium compared to the main base REO ores (Table 6). ... 

The lanthanum phosphate phosphor is usually prepared by starting with a highly purified coprecipitated oxide of lanthanum, cerium, and terbium blended with a slight excess of the stoichiometric amount of diammonium acid phosphate. Unlike the case of the aluminate phosphor, firing is carried out in an only slightly reducing or a neutral atmosphere of nitrogen at a temperature 1000° C. Also this phosphor is typically made with the addition of a flux,... 

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