Terbium(III,IV) oxide

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Terbium(III,IV) oxide
Terbium(III,IV) oxide
Names
IUPAC name
Tetraterbium heptaoxide
Other names
Terbium(III,IV) oxide,
Terbium peroxide
Identifiers
3D model (
JSmol
)
ECHA InfoCard
100.031.675 Edit this at Wikidata
  • InChI=1S/7O.4Tb
  • O=[Tb]O[Tb](=O)O[Tb](=O)O[Tb]=O
Properties
Tb4O7
Molar mass 747.6972 g/mol
Appearance Dark brown-black
hygroscopic solid.
Density 7.3 g/cm3
Melting point Decomposes to Tb2O3
Insoluble
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Oxidising agent.
Related compounds
Other cations
Terbium(III) oxide
Terbium(IV) oxide
Related compounds
Cerium(IV) oxide
Praseodymium(III,IV) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Terbium(III,IV) 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 oxides: Tb2O3, TbO2
, and Tb6O11.

Synthesis

Tb4O7 is most often produced by ignition of the oxalate or the sulfate in air.[1] 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

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.[2]

Tb4O7 reacts with atomic oxygen to produce TbO2, but more convenient preparations are available.[3]

Tb
4
O
7
(s) + 6 HCl (aq) → 2 TbO
2
(s) + 2 TbCl
3
(aq) + 3 H
2
O
(l)

. 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.

Anhydrous terbium(III) chloride can be produced by the

ammonium chloride route[4][5][6]
In the first step, terbium oxide is heated with ammonium chloride to produce the ammonium salt of the pentachloride:

Tb4O7 + 22 NH4Cl → 4 (NH4)2TbCl5 + 7 H2O + 14 NH3

In the second step, the ammonium chloride salt is converted to the trichlorides by heating in a vacuum at 350-400 °C:

(NH4)2TbCl5 → TbCl3 + 2 HCl + 2 NH3

References

  1. .
  2. .
  3. .
  4. ^ Brauer, G., ed. (1963). Handbook of Preparative Inorganic Chemistry (2nd ed.). New York: Academic Press.
  5. ^ Meyer, G. (1989). "The Ammonium Chloride Route to Anhydrous Rare Earth Chlorides—The Example of Ycl 3". The Ammonium Chloride Route to Anhydrous Rare Earth Chlorides-The Example of YCl3. Inorganic Syntheses. Vol. 25. pp. 146–150. .
  6. .

Further reading