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| Names | |
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| IUPAC name
Cerium(III) sulfide
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Other names
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.031.445 |
| EC Number |
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| Ce2S3 | |
| Molar mass | 375.73 g/mol |
| Appearance | Red/burgundy/black crystals (depending on polymorph) |
| Density | 5.18 g/cm3 |
| Melting point | 1,840 to 1,940 °C (3,340 to 3,520 °F; 2,110 to 2,210 K) |
| Boiling point | decomposes (at 2300 °C) |
| insoluble | |
| Solubility | soluble in warm formic or acetic acid soluble in cold dil. HCl, HNO3 or H2SO4 |
| Band gap | 2.06 eV (γ-Ce2S3) |
Refractive index (nD)
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2.77 (589 nm) |
| Structure | |
| orthorhombic (α-Ce2S3) tetragonal (β-Ce2S3) cubic (γ-Ce2S3) | |
| Thermochemistry | |
Heat capacity (C)
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126.2 J·mol−1·K−1 |
Std enthalpy of
formation (ΔfH⦵298) |
-1260 kJ·mol−1 |
Gibbs free energy (ΔfG⦵)
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-1230 kJ·mol−1 |
| Hazards | |
| GHS labelling: | |
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| Warning | |
| H315, H319, H335 | |
| P261, P280, P305+P351+P338 | |
| Related compounds | |
Other anions
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Cerium(III) oxide, Cerium(III) selenide, Cerium(III) oxyselenide |
Other cations
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Samarium(III) sulfide, Praseodymium(III) sulfide |
Related compounds
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Cerium(II) sulfide, Ce3S4, Cerium disulfide, Ce2O2S |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cerium(III) sulfide, also known as cerium sesquisulfide, is an inorganic compound with the formula Ce2S3. It is the sulfide salt of cerium(III) and exists as three polymorphs with different crystal structures.[1][2][3]
Its high melting point (comparable to silica or alumina) and chemically inert nature have led to occasional examination of potential use as a refractory material for crucibles, but it has never been widely adopted for this application.[2]
The distinctive red colour of two of the polymorphs (α- and β-Ce2S3) and aforementioned chemical stability up to high temperatures have led to some limited commercial use as a red pigment (known as cerium sulfide red).[3]
Synthesis
The oldest syntheses reported for cerium(III) sulfide follow a typical rare earth sesquisulfide formation route, which involves heating the corresponding cerium sesquioxide to 900–1100 °C in an atmosphere of hydrogen sulfide:[1][4]
- Ce2O3 + 3 H2S → Ce2S3 + 3 H2O
Newer synthetic procedures utilise less toxic carbon disulfide gas for sulfurisation, starting from cerium dioxide which is reduced by the CS2 gas at temperatures of 800–1000 °C:[2]
- 6 CeO2 + 5 CS2 → 3 Ce2S3 + 5 CO2 + SO2
Polymorphs
| Polymorph | T of formation | Colour | Crystal system | Space group | Lattice constants |
|---|---|---|---|---|---|
| α-Ce2S3 | <900 °C | burgundy | Othorhombic | Pnma (No. 62) | a=7.63 Å, b=4.12 Å, c=15.71 Å |
| β-Ce2S3 | 900–1200 °C | red | Tetragonal | I41/acd (No. 142) | a=15.37 Å, c=20.35 Å |
| γ-Ce2S3 | >1200 °C | black | Cubic | I43d (No. 220) | a=8.63 Å |
Ce2S3 exists in three polymorphic forms: α-Ce2S3 (orthorhombic, burgundy colour), β-Ce2S3 (tetragonal, red colour), γ-Ce2S3 (cubic, black colour).[1][2][3] They are analogous to the crystal structures of the likewise trimorphic Pr2S3 and Nd2S3.[2]
Following the synthetic procedures given above will yield mostly the α- and β- polymorphs, with the proportion of α-Ce2S3 increasing at lower temperatures (~700–900 °C) and with longer reaction times.[2][3] The α- form can be irreversibly transformed into β-Ce2S3 by vacuum heating at 1200 °C for 7 hours. Then γ-Ce2S3 is obtained from sintering of β-Ce2S3 powder via hot pressing at an even higher temperature (1700 °C).[2]
α polymorph
The α polymorph of cerium(III) sulfide has the same structure as α-Gd2S3. It contains both 7-coordinate and 8-coordinate cerium ions, Ce3+, with monocapped and bicapped trigonal prismatic coordination geometry, respectively. The sulfide ions, S2−, are 5-coordinate.[5] Two thirds of them adopt a square pyramidal geometry and one third adopt a trigonal bipyramidal geometry.[6]
| Cerium Ce1 coordination | Cerium Ce2 coordination | Sulfur S1 coordination | Sulfur S2 coordination | Sulfur S3 coordination |
|---|---|---|---|---|
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γ polymorph
The γ polymorph of cerium(III) sulfide adopts a cation-deficient form of the Th3P4 structure. 8 out the 9 metal positions in the Th3P4 structure are occupied by cerium in γ-Ce2S3, with the remainder as vacancies. This composition can be represented by the formula Ce2.667□0.333S4. The cerium ions are 8-coordinate while the sulfide ions are 6-coordinate (distorted octahedral).[5][6]
Reactions
Some reported reactions of cerium(III) sulfide are with bismuth compounds in order to form superconducting crystalline materials of the M(O,F)BiS2 family (for M=Ce).[7]
The reaction of Ce2S3 with Bi2S3 and Bi2O3 in a sealed tube at 950 °C gives the parent compound CeOBiS2:
- 3 Ce2S3 + Bi2S3 + 2 Bi2O3 → 6 CeOBiS2
This material is superconducting on its own, but the properties can be enhanced if it is doped with fluoride by including BiF3 in the reaction mixture.[7]
Applications
Refractory material
Cerium(III) and cerium(IV) sulfides were first investigated in the 1940s as part of the Manhattan project, where they were considered -but eventually not adopted- as advanced refractory materials.[2] Their suggested application was as the material in crucibles for the casting of uranium and plutonium metal.[2][4]
Although the sulfide's properties (high melting point and large, large negative ΔfG° and chemical inertness) are suitable and cerium is a relatively common element (66 ppm, about as much as copper), the danger of the traditional H2S-involving production route and the difficulty in controlling the formation of the resulting Ce2S3/CeS solid mixture meant that the compound was ultimately not developed further for such applications.[2]
Pigment and other uses
The main non-research use of cerium(III) sulfide is as a specialty inorganic pigment.[3] The strong red hues of α- and β-Ce2S3, non-prohibitive cost of cerium, and chemically inert behaviour up to high temperature are the factors which make the compound desirable as a pigment.
Regarding other applications, the γ-Ce2S3 polymorph has a band gap of 2.06 eV and high Seebeck coefficient, thus it has been proposed as a high-temperature semiconductor for thermoelectric generators.[2] A practical implementation thereof has not been demonstrated so far.
References
- ^ a b c Banks, E.; Stripp, K. F.; Newkirk, H. W.; Ward, R. (1952). "Cerium(III) Sulfide and Selenide and Some of their Solid Solutions1". Journal of the American Chemical Society. 74 (10): 2450–2453. doi:10.1021/ja01130a002. ISSN 0002-7863.
- ^ a b c d e f g h i j k Hirai, Shinji; Shimakage, Kazuyoshi; Saitou, Yasushi; Nishimura, Toshiyuki; Uemura, Yoichiro; Mitomo, Mamoru; Brewer, Leo (1998). "Synthesis and Sintering of Cerium(III) Sulfide Powders". Journal of the American Ceramic Society. 81 (1): 145–151. doi:10.1111/j.1151-2916.1998.tb02306.x. ISSN 1551-2916.
- ^ a b c d e Kariper, I. A. (2014). "Synthesis and characterization of cerium sulfide thin film". Progress in Natural Science: Materials International. 24 (6). Elsevier: 663–670. doi:10.1016/j.pnsc.2014.10.005. ISSN 1002-0071.
- ^ a b Hadden, Gavin, ed. (1946). "Chapter 11 - Ames Project". Manhattan District History. Vol. 4 - Auxiliary Activities. Washington, D.C.: US Army Corps of Engineers.
- ^ a b c Schleid, Thomas; Lauxmann, Petra (1999). "Röntgenstrukturanalysen an Einkristallen von Ce2S3 im A- und C-Typ". Z. Anorg. Allg. Chem. 625 (7): 1053–1055. doi:10.1002/(SICI)1521-3749(199907)625:7<1053::AID-ZAAC1053>3.0.CO;2-Z.
- ^ a b Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. pp. 766–767. ISBN 978-0-19-965763-6.
- ^ a b Tanaka, Masashi; Nagao, Masanori; Matsumoto, Ryo; Kataoka, Noriyuki; Ueta, Ikuo; Tanaka, Hiromi; Watauchi, Satoshi; Tanaka, Isao; Takano, Yoshihiko (2017-10-25). "Superconductivity and its enhancement under high pressure in "F-free" single crystals of CeOBiS2". Journal of Alloys and Compounds. 722: 467–473. arXiv:1706.03590. doi:10.1016/j.jallcom.2017.06.125. ISSN 0925-8388. S2CID 119537216.
