Terbium(III,IV) oxide
Encyclopedia
Terbium oxide, occasionally called tetraterbium heptaoxide, has the formula Tb4O7, though some texts refer to it as TbO1.75. There is some debate as to whether it is a discrete compound, or simply one phase in an interstitial
oxide system. Tb4O7 is one of the main commercial terbium
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
s: Tb2O3
, TbO2, and Tb6O11.
at or the sulfate
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.
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
catalyst in reactions involving oxygen. It was found as early as 1916 that hot Tb4O7 catalyses the reaction of coal gas
(CO
+ H2
) with air, leading to incandescence and often ignition.
Tb4O7 reacts with atomic oxygen to produce TbO2, but a more convenient preparation of TbO2 is by disproportionation
of Tb4O7. This is performed by refluxing with an excess of an equal mixture of concentrated acetic acid
and hydrochloric acid
s for 30 minutes, producing terbium(III) chloride
and water.
Tb4O7 reacts with other hot concentrated acids to produce terbium(III) salts. For example, reaction with sulfuric acid
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.
Interstitial
An interstitial space or interstice is an empty space or gap between spaces full of structure or matter.In particular, interstitial may refer to:-Physical sciences:...
oxide system. Tb4O7 is one of the main commercial terbium
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, ductile and soft enough to be cut with a knife...
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
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
s: Tb2O3
Terbium(III) oxide
Terbium oxide, also known as terbium sesquioxide, is a sesquioxide of the rare earth metal terbium, having chemical formula . It is a p-type semiconductor when doped with calcium, and may be prepared by the reduction of in hydrogen at 1300 °C for 24 hours.It is a p-type semiconductor.It is a basic...
, TbO2, and Tb6O11.
Synthesis
Tb4O7 is most often produced by ignition of the oxalateOxalate
Oxalate , is the dianion with formula C2O42− also written 22−. Either name is often used for derivatives, such as disodium oxalate, 2C2O42−, or an ester of oxalic acid Oxalate (IUPAC: ethanedioate), is the dianion with formula C2O42− also written (COO)22−. Either...
at or the sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
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 O2Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
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
Vanadium(V) oxide
Vanadium oxide is the chemical compound with the formula V2O5. Commonly known as vanadium pentoxide, this brown/yellow solid is the most stable and common compound of vanadium. Upon heating it reversibly loses oxygen...
, allows it to work like V2O5 as a redox
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
catalyst in reactions involving oxygen. It was found as early as 1916 that hot Tb4O7 catalyses the reaction of coal gas
Coal gas
Coal gas is a flammable gaseous fuel made by the destructive distillation of coal containing a variety of calorific gases including hydrogen, carbon monoxide, methane and volatile hydrocarbons together with small quantities of non-calorific gases such as carbon dioxide and nitrogen...
(CO
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
+ H2
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
) with air, leading to incandescence and often ignition.
Tb4O7 reacts with atomic oxygen to produce TbO2, but a more convenient preparation of TbO2 is by disproportionation
Disproportionation
Disproportionation, also known as dismutation is used to describe a specific type of redox reaction in which a species is simultaneously reduced and oxidized so as to form two different products....
of Tb4O7. This is performed by refluxing with an excess of an equal mixture of concentrated acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
and hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
s for 30 minutes, producing terbium(III) chloride
Terbium(III) chloride
Terbium chloride is a chemical compound. In the solid state TbCl3 has the YCl3 layer structure. Terbium chloride frequently forms a hexahydrate.-Hazards:Terbium chloride causes hyperemia of the iris....
and water.
- (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
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
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.