Cerium(III) tungstate is an inorganic compound of cerium and the tungstate ion, with the chemical formula Ce2(WO4)3. It is a whitish, water-insoluble crystalline solid.
Preparation Cerium(III) tungstate can be prepared by precipitation from aqueous solutions of cerium(III) nitrate and sodium tungstate. This method has also been used to prepare nanoscale Ce2(WO4)3.
A simplified precipitation reaction is:
2 Ce(NO3)3 + 3 Na2WO4 → Ce2(WO4)3↓ + 6 NaNO3
Single crystals have been grown from molten mixtures of cerium(IV) oxide and tungsten trioxide.
The overall reaction may be written as:
4 CeO2 + 6 WO3 → 2 Ce2(WO4)3 + O2
The formation of Ce(III) from Ce(IV) during this high-temperature synthesis was supported by thermogravimetric and magnetic measurements.
Structure and properties Cerium(III) tungstate crystallizes in the monoclinic crystal system, in space group C2/c (No. 15), and is isotypic with europium(III) tungstate. The unit-cell parameters are a = 7.813(4) Å, b = 11.720(2) Å, c = 11.586(3) Å and β = 109.36(3)°, with four formula units per unit cell.
The crystal structure contains one crystallographically distinct Ce3+ site. Each cerium ion is coordinated by eight oxygen atoms in a distorted capped trigonal-prismatic environment. Unlike many simple tungstates containing only tetrahedral WO4 groups, Ce2(WO4)3 contains both WO4 tetrahedra and square-pyramidal WO5 units.
Nanocrystalline Ce2(WO4)3 exhibits optical absorption and photoluminescence characteristic of tungstate-containing materials. A broad blue emission has been attributed primarily to electronic transitions associated with the tungstate groups.
The optical band gap of nanocrystalline samples depends on preparation and calcination conditions, decreasing as calcination temperature is increased.
Applications Cerium(III) tungstate has been investigated as a luminescent and optoelectronic material. Its blue photoluminescence has led to research into its potential use in near-ultraviolet-excited light-emitting devices and related optical applications.
Nanostructured Ce2(WO4)3 and composites containing it have also been investigated as photocatalysts for degradation of organic contaminants.
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