terbium

Tb. Atomic number 65. Lanthanide element in group ³ of the periodic table with electron configuration [Xe] ^4f96s2 . One of the rare earth elements of the yttrium group. It is a mononuclear element with only one stable nuclide, mass number 159. Radioactive isotopes with mass numbers between 135 and 171 are known. It was isolated from yttria by CG Mosander in 1843. The element's name comes from the name of the village where the mineral yttria was discovered, ytterby, but he divided the name into thirds and named the three elements he found in yttria yttrium, terbium, and erbium. It took a long time to confirm the name, and the name terbium was finally confirmed in 1878, and was given to the element he originally called erbium.
It is found in gadolinite and cercite, and its abundance in the earth's crust is 0.6 ppm, which is one of the very low levels among rare earth elements. China is the main producer of rare earth elements in general, accounting for about 98% (2006), and medium and heavy rare earth elements such as terbium are concentrated in southern China. It is an important resource with a significantly high monopoly. A silver-gray metal. It has a hexagonal close-packed structure (α modification), an orthorhombic system above -53 °C, and a body-centered cubic lattice structure above 1317 °C. It has a melting point of 1356 °C and a boiling point of 3123 °C. Its density is 8.229 g cm ^-3 (20 °C). Its first ionization energy is 5.864 eV. It dissolves gradually in water, and in hot water and acid, releasing hydrogen. Its oxidation states are 3 and 4. The compound is colorless. It is strongly paramagnetic. The electron configuration of Tb3 ⁺ is ^4f8 , and that of Tb4 ⁺ is ^4f7 with half-filled f orbitals, making it less stable than Ce4 ⁺ in _the [Xe] configuration. ^TbⅢ _compounds are the norm, _and ^TbⅣ compounds are less well known. ^TbⅣF4 is _a colorless solid obtained by reacting ^TbⅢF3 _{with F2 at} temperatures above ₃₀₀ ℃. ^TbⅣO2 is obtained by reacting ^TbⅢ2O3 with atomic oxygen at 450℃. _Tb4O7 is considered to be diterbium(Ⅳ) heptoxide.
Tb is used as an activator for green phosphors in cathode ray tubes and other devices, TbDyFe alloys are used as super-magnetic elastic materials in printer heads, and TbFeCo alloys are used as magneto-optical recording materials. Currently, its most important use is as an additive to increase the coercive force of neodymium magnets (see other terms: rare earth magnets) and improve their high-temperature properties, and prices are soaring with the rapid increase in demand for neodymium magnets. [CAS 7440-27-9]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

Tb．原子番号65の元素．電子配置[Xe]4f ⁹6s²の周期表3族ランタノイド元素．希土類元素イットリウム族の一つ．安定核種は質量数159のみの単核種元素．質量数135～171の放射性同位体が知られている．1843年，C.G. Mosanderによりイットリア中から分離された．元素名は鉱物yttriaの見いだされた村名ytterbyからであるが，かれはこの名前を三分割してyttria中に発見した三元素の名称をyttrium，terbium，erbiumとした．確認に手間どり1878年に最終的に確定した名称テルビウムはかれが当初エルビウムとよんだ元素に与えられた．
希土類元素中とくに存在量が少ない．ガドリン石，セル石に含まれる．地殻中の存在度0.6 ppm は希土類元素中で非常に低い部類に属する．希土類元素全般の主要産出国は中国で約98％(2006年)を占めており，テルビウムなどの中重希土類は華南地域に集中している．いちじるしく寡占度の高い重要資源である．銀灰色の金属．六方最密構造(α変態)，－53 ℃ 以上で斜方晶系，1317 ℃ 以上で体心立方格子構造．融点1356 ℃，沸点3123 ℃．密度8.229 g cm^－3(20 ℃)．第一イオン化エネルギー5.864 eV．水に徐々に溶解，熱水，酸には溶解して水素を発生する．酸化数3，4．化合物の色は無色．強い常磁性を示す．電子配置は Tb^3＋ は4f ⁸，Tb^4＋ はf軌道が半分満たされた4f ⁷で，[Xe]配置の Ce^4＋ ほどに安定ではない．Tb^Ⅲ化合物が主で，Tb^Ⅳ化合物はあまり知られていない．Tb^Ⅳ F₄はTb^Ⅲ F₃と F₂ を300 ℃ 以上で反応させると得られる無色の固体．Tb^Ⅳ O₂はTb^Ⅲ₂O₃を450 ℃ で原子状酸素と反応させると得られる．Tb₄O₇は七酸化二テルビウム(Ⅳ)二テルビウム(Ⅲ)とされている．
Tbはブラウン管他用緑色蛍光体賦活剤として，TbDyFe合金は超磁気伸縮性材料でプリンターヘッドに，TbFeCo合金は磁気光学記録材料として用いられる．現在，もっとも重要な用途はネオジム磁石([別用語参照]希土類磁石)の保磁力を高め高温特性を改善するための添加剤で，ネオジム磁石需要の急増に伴って価格が急騰している．[CAS 7440-27-9]

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