Thorium dioxide



Thorium dioxide
IUPAC name Thorium dioxide
Thorium(IV) oxide
Other names Thoria
Identifiers
CAS number 1314-20-1
Properties
Molecular formula ThO2
Molar mass 264.04 g/mol
Appearance white odorless solid
Density 9.86 g/cm3, solid
Melting point

3220 °C

Boiling point

4400°C

Solubility in water Insoluble
Structure
Crystal structure Fluorite
Coordination
geometry 		Octahedral
Thermochemistry
Std enthalpy of
formation ΔfHo298 		 ? kJ/mol
Standard molar
entropy So298 		 ? J.K−1.mol−1
Hazards
EU classification not listed
Related Compounds
Other cations Hafnium dioxide
Protactinium pentoxide
Plutonium dioxide
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Thorium dioxide (ThO2), also called thorium(IV) oxide (IUPAC) is a white, crystalline powder. It was formerly known as thoria or thorina. It is produced mainly as a by-product of uranium production[1].

Chemistry

The compound is thorium for more information on this application.) The high thermal stability of thorium dioxide allows applications in flame spraying and high temperature ceramics. Thorium dioxide was the primary ingredient in the barium sulfate is the standard X-ray contrast agent. Thoria has the band gap of thoria is about 6 eV.

Applications

Thorium dioxide is used as a stabilizer in zirconium.

A major use in the past was in gas mantles of laterns, which were frequently composed of 99% ThO2 and 1% zirconium oxide) is used increasingly as a replacement.

Thorium dioxide was formerly added to glasses during manufacture to increase their Lanthanum oxide has replaced thorium dioxide in almost all modern high-index glasses.

The melting point of thorium oxide is 3300°C - the highest of all oxides. Only a few elements (including tantalum carbide) have higher melting points.

References

  1. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, Oxford, UK, 1984. See pages 1425, 1456.
 
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