Terbium compounds are compounds formed by the lanthanide metal terbium (Tb). Terbium generally exhibits the +3 oxidation state in these compounds, such as in TbCl3, Tb(NO3)3 and Tb(CH3COO)3. Compounds with terbium in the +4 oxidation state are also known, such as TbO2 and BaTbF6.无机化学丛书. pp 187-188. 1.2.3 氧化态及电极电势 Terbium can also form compounds in the 0, +1 and +2 oxidation states.
The trivalent terbium ion (Tb3+) is generally colorless in aqueous solution, and when it is irradiated by certain wavelengths of ultraviolet light (such as 254 nm or 365 nm) in solution or crystal form, it will emit green fluorescence. This property has given rise to applications in fields such as optics. The tetravalent terbium ion (Tb4+) is non-luminescent and its coexistence with Tb3+ will reduce the green emission of Tb3+.
Properties of terbium compounds Formula appearance symmetry space group No a (nm) b (nm) c (nm) density, g/cm3 TbBr3 white powder (hexahydrate) trigonal R 148 4.62americanelements.com: Terbium Bromide TbCl3 white powder hexagonal P63/m 176 4.35 TbF3 white solid hexagonal无机化学丛书 第七卷 钪 稀土元素. 科学出版社. pp 212. 表 22.24 无水卤化物的物理常数. 7.035 6.875 7.23americanelements.com: Terbium Fluoride Tb(OH)3 white solid《无机化学丛书》. 第七卷 钪 稀土元素. 易宪武 等主编. 科学出版社. P168~171. (2)氢氧化物 TbI3 hydroscopic crystals trigonal R 148 5.2 Tb(NO3)3 colourless crystals (hexahydrate) monoclinic P21/c 14 1.2870 1.6590 2.8723 Tb2O3 white crystals cubic Ia 206 1.057 7.91 TbO2 dark-coloured cubic TbP black crystals cubic Fmm 225 0.56402 6.82 Tb4O7 dark brown-black solid orthorhombic R 148 6.5082 7.3 Tb11O20 solid triclinic P 2 6.50992 9.8298 6.4878 TbAsO4 solid orthorhombic Fddd 70 7.09 6.32 TbAsO4 solid tetragonal I41/amd 141 10.081 9.957 6.321 TbSbO4 green (under UV light) monoclinic P21/m 11 TbSe yellow-red solidOlcese, Giorgio L. Structure and magnetic properties of MX compounds from terbium and metalloids of the Groups V and VI. Atti Accad. Nazi. Lincei Rend. Classe Sci. Fis. Mat. e Nat., 1961. 30: 195-200. cubic Fmm 225
Chalcogenides
Oxides
Terbium has a variety of oxides. The most easily obtained is terbium(III,IV) oxide, which can be produced by the decomposition of terbium compounds such as the hydroxide,Chen Shouchun. Important Inorganic Chemical Reactions. Shanghai Science and Technology Press, 1994. pp 1304-1305. the oxalate and the p-aminobenzoate. Terbium(III,IV) oxide, because the oxide contains both trivalent terbium and tetravalent terbium, can be decomposed by reacting with nitric acid to produce terbium(III) nitrate, releasing oxygen in the progress:
2 Tb4O7 + 24 HNO3 → 8 Tb(NO3)3 + 12 H2O + O2↑
It is refluxed in a mixture of acetic acid and hydrochloric acid, which can separate trivalent and tetravalent terbium:
Tb4O7 + 6 HCl → 2 TbO2 + 2 TbCl3 + 3 H2O
It reacts with dicyandiamide at a high temperature to obtain Tb2O2CN2.
Another common oxide of terbium is terbium(III) oxide, which can be obtained from the reduction of hydrogen from terbium(III,IV) oxide at 1300 °C. A p-type semiconductor is formed after doping with calcium.
Terbium(IV) oxide can be prepared by treating terbium(III,IV) oxide with dilute hydrochloric acid,Inorganic Chemistry Series. pp 244-257 its hydrate TbO2·xH2O can be obtained by oxidizing terbium(III) hydroxide with potassium persulfate in the presence of silver nitrate. Terbium(IV) oxide can form mixed crystals with praseodymium(IV) oxide.
Other chalcogenides
Terbium(III) sulfide is one of the sulfides of terbium, which can be obtained by reacting with sulfur in a stoichiometric ratio. It can also be obtained by reacting terbium(III,IV) oxide with carbon disulfide and hydrogen sulfide at high temperature. It reacts with hydrofluoric acid solution to give terbium(III) fluoride hemihydrate. Terbium(III) selenide can be obtained by the reaction of terbium polyselenide TbSe1.9 with metal terbium, which can form black needle-like crystals with U2S3 structure and space group Pnma. Terbium monochalcogenides, TbZ (Z = S, Se or Te), can be prepared by directly reacting terbium with the corresponding chalcogen. These chalcogenides are black and have a NaCl structure. They have metallic conductivity and consist of Ln3+ and Z2- ions with 1 electron from each cation delocalized in a conduction band.
Halides and halogen complexes
Terbium can form four trihalides in the form TbX3 (X=F, Cl, Br, I), which, except the fluoride, are easily soluble in water, and are strong electrolytes in water. They can be prepared by reacting terbium with the corresponding halogen:Terbium: reactions of elements . WebElements. [2017-4-10]
[a white substance] [a white substance] [a white substance]
Anhydrous terbium halides can be prepared by reacting oxides or halides hydrates:Inorganic Chemistry Series. pp 210-215. 2. Halides Tb2O3 + 6 NH4Cl → 2 TbCl3 + 3 H2O + 6 NH3↑ TbCl3·6H2O + 6 SOCl2 → TbCl3 + 6 SO2↑ + 12 HCl↑
Terbium(II) halides are obtained by annealing Tb(III) halides in presence of metallic Tb in tantalum containers. Terbium also forms a sesquichloride , which can be further reduced to TbCl by annealing at 800 °C. This terbium(I) chloride forms platelets with layered graphite-like structure.
Terbium(IV) fluoride is the only halide that tetravalent terbium can form, and has strong oxidizing properties. It is also a strong fluorinating agent, emitting relatively pure atomic fluorine when heated, rather than the mixture of fluoride vapors emitted from cobalt(III) fluoride or cerium(IV) fluoride. It can be obtained by reacting terbium(III) chloride or terbium(III) fluoride with fluorine gas at 320 °C: 2 TbF3 + F2 → 2 TbF4 When TbF4 and CsF is mixed in a stoichiometric ratio, in a fluorine gas atmosphere, CsTbF5 is obtained. It is an orthorhombic crystal, with space group Cmca, with a layered structure composed of [TbF8]4− and 11-coordinated Cs+. The compound BaTbF6 can be prepared in a similar method. It is an orthorhombic crystal, with space group Cmma. The compound [TbF8]4− also exists.
Organoterbium compounds
Organoterbium compounds are a class of organic metal compounds containing Tb-C bonds. The cyclopentadienyl complexes of terbium were studied in the early stage. They can be prepared by the reaction of sodium cyclopentadienide and anhydrous terbium halide in tetrahydrofuran, such as:无机化学丛书. pp 338. 2.3.7 稀土元素有机化合物.
TbCl3 + 3 C5H5Na → (C5H5)3Tb + 3 NaCl TbI2 + 2 (C5HiPr4)Na → (C5HiPr4)2Tb + 2 NaI
However, this compound has limited usage and academic interest.
Like the other lanthanides, metal-carbon σ bonds are found in alkyls of terbium such as [TbMe6]3− and Tb[CH(SiMe3)2]3. The alkyls and aryls can be prepared by metathesis in tetrahydrofuran on ether solutions:
TbCl3 + 3 LiR → TbR3 + 3 LiCl TbCl3 + 4 LiR → Li[TbR4] + 3 LiCl3
Other compounds
Oxoacid salts
Terbium(III) sulfate can be obtained by the reaction of terbium(III,IV) oxide and concentrated sulfuric acid. It can crystallize colorless octahydrate crystals in water, which is isostructural with the corresponding praseodymium compound. The anhydrate can be obtained by heating the octahydrate, and an exothermic reaction occurs when the anhydrate is rehydrated.无机化合物合成手册. pp 258-259. 819 硫酸盐. Terbium(III) hydroxide can be obtained by reacting terbium with water. It reacts with acids to produce terbium(III) salts. It decomposes to TbO(OH) at an elevated temperature, and upon further heating, will decompose to terbium(III) oxide.
Terbium(III) nitrate can be obtained by reacting terbium(III) oxide with nitric acid and crystallizing. The crystals are dried with 45~55% sulfuric acid to obtain the hexahydrate. The basic salt TbONO3 can be obtained by heating the hydrate, and its anhydrate can be obtained by the reaction of terbium(III) oxide and dinitrogen tetroxide.无机化合物合成手册. pp 260-261. 820 硝酸盐. Terbium(III) phosphate can be obtained by the reaction of diammonium hydrogen phosphate and terbium(III) nitrate, and the reaction produces a hexagonal monohydrate, which can emit the characteristic green light of terbium (543 nm) under the excitation of 355 nm wavelength. It can also be obtained by the reaction of sodium phosphate and terbium(III) chloride in solution, and the precipitated dihydrate is calcined at 800 °C to obtain the anhydrous form.Kalieva, K.; Stretkova, Z. V.; Babynina, N. A.; Gordienko, L. N.; Votoyarov, M.; Yakimov; Sakavov, I. E.; Mustaev, A. K. X-ray diffraction studies of praseodymium, neodymium, europium, terbium, dysprosium, erbium, holmium, and terbium orthophosphates. (in Russian) Tr. Kirg. Univ., Ser. Khim. Nauk, 1972. (2): 84-89. Terbium(III) arsenate is an orthorhombic crystal at 77 K with space group Fddd, and undergoes a phase transition at 27.7 K to form a tetragonal crystal with space group I41/amd, which is a ferromagnet below 1.5 K. It can be produced by reacting sodium arsenate and terbium(III) chloride. Terbium(III) antimonate (TbSbO4) is a monoclinic crystal with space group P21/m (No. 11).
Terbium(III) carbonate can be obtained by reacting terbium(III) chloride with saturated carbon dioxide solution in sodium bicarbonate, and the product also needs to be washed with water saturated with carbon dioxide. The germanates TbIII13(GeO4)6O7(OH) and K2TbIVGe2O7 can be synthesized at high temperature and pressure, and they are colorless crystals of trigonal and monoclinic systems, respectively. The tetrahydrate of terbium(III) acetate can lose hydration at 60 °C, obtaining the anhydrate at 180 °C, which starts to decompose at 220 °C, forming terbium oxide at 650 °C.
Terbium borate can be obtained by reacting terbium oxide with boric acid: 2 Tb4O7 + 8 H3BO3 → 8 TbBO3 + 12 H2O + O2↑
The single crystal of its hexagonal phase can be obtained by the Czochralski method; it can also form a solid of the triclinic system, which can be obtained by the sol-gel method. The composite borates TbFe3(BO3)4 and TbAl3(BO3)4 can also be obtained by a similar method. Terbium(III) oxide, terbium(III) chloride and boron trioxide react in a caesium chloride solution to obtain terbium oxychloride borate Tb4O4Cl(BO3), which is a monoclinic crystal with space group P21/n. Both aluminate Tb3Al5O12 and gallate Tb3Ga5O12 can be used as magneto-optical materials.
Pnictides
All the terbium pnictides form crystals of the cubic crystal system, with the space group of Fm3m. Terbium phosphide can be obtained by reacting sodium phosphide and anhydrous terbium(III) chloride at 700 to 800˚C. It undergoes a phase transition at 40 GPa from a NaCl-structure to a CsCl-structure. It can be sintered with zinc sulfide to make a green phosphor layer.
Alloys
Terfenol-D
Terfenol-D is an alloy of terbium, iron and dysprosium, with the formula of . It was initially developed in the 1970s by the Naval Ordnance Laboratory in the United States. The technology for manufacturing the material efficiently was developed in the 1980s at Ames Laboratory under a U.S. Navy-funded program. It has the highest magnetostriction of any alloy, with up to 0.002 m/m at saturation. It possess nearly zero magnetocrystalline anisotropy and so exhibits very large magnetostriction at low magnetic fields. Terfenol-D is mostly used for its magnetostrictive properties, in which it changes shape when exposed to magnetic fields in a process called magnetization. Magnetic heat treatment is shown to improve the magnetostrictive properties of Terfenol-D at low compressive stress for certain ratios of Tb and Dy.
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