Terbium(III,IV) oxide, occasionally called tetraterbium heptaoxide, has the formula Tb₄O₇, though some texts refer to it as TbO_1.75. There is some debate as to whether it is a discrete compound, or simply one phase in an

interstitial An interstitial space or interstice is a space between structures or objects. In particular, interstitial may refer to: Biology * Interstitial cell tumor * Interstitial cell, any cell that lies between other cells * Interstitial collagenase ...

oxide system. Tb₄O₇ is one of the main commercial

terbium Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with w ...

compounds, and the only such product containing at least some Tb(IV) (terbium in the +4 oxidation state), along with the more stable Tb(III). It is produced by heating the metal oxalate, and it is used in the preparation of other terbium compounds. Terbium forms three other major

oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...

s: Tb₂O₃, TbO₂, and Tb₆O₁₁.

Synthesis

Tb₄O₇ is most often produced by ignition of the

oxalate Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl ...

at or the

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

in air. The oxalate (at 1000 °C) is generally preferred, since the sulfate requires a higher temperature, and it produces an almost black product contaminated with Tb₆O₁₁ or other oxygen-rich oxides.

Chemical properties

Terbium(III,IV) oxide loses O₂ when heated at high temperatures; at more moderate temperatures (ca. 350 °C) it reversibly loses oxygen, as shown by exchange with¹⁸O₂. This property, also seen in Pr₆O₁₁ and V₂O₅, allows it to work like V₂O₅ as a

redox Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

in reactions involving oxygen. It was found as early as 1916 that hot Tb₄O₇ catalyses the reaction of

coal gas Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. It is produced when coal is heated strongly in the absence of air. Town gas is a more general term referring to manufactured gaseous ...

( CO + H₂) with air, leading to incandescence and often ignition. Tb₄O₇ reacts with atomic oxygen to produce TbO₂, but more convenient preparations are available. : (s) + 6 HCl (aq) → 2 (s) + 2 (aq) + 3 (l) . Tb₄O₇ reacts with other hot concentrated acids to produce terbium(III) salts. For example, reaction with

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...

gives terbium(III) sulfate. Terbium oxide reacts slowly with hydrochloric acid to form terbium(III) chloride solution, and elemental chlorine. At ambient temperature, complete dissolution might require a month; in a hot water bath, about a week. Anhydrous terbium(III) chloride can be produced by the ammonium chloride route In the first step, terbium oxide is heated with ammonium chloride to produce the ammonium salt of the pentachloride: :Tb₄O₇ + 22NH₄Cl → 4(NH₄)₂TbCl₅ + 7H₂O + 14NH₃ In the second step, the ammonium chloride salt is converted to the trichlorides by heating in a vacuum at 350-400 ºC: :(NH₄)₂TbCl₅ → TbCl₃ + 2HCl + 2NH₃

Synthesis

Chemical properties

References

Further reading