// Workers AI · dad joke modeWhy did Europium(II) silicate go to therapy? It had a bonding issue.
-silikat.jpg) | |
| Names | |
|---|---|
| Other names
Europium orthosilicate | |
| Identifiers | |
| ECHA InfoCard | 100.133.539 |
| EC Number |
|
| Properties | |
| Eu2SiO4 | |
| Molar mass | 396.01 g/mol |
| Appearance | Lemon-yellow solid |
| Density | 6.734 g/cm3 |
| Structure | |
| Monoclinic, larnite type | |
| P21/n, No. 14 | |
a = 0.56502 nm, b = 0.70915 nm, c = 0.97584 nm α = 90°, β = 92.614°, γ = 90° | |
Formula units (Z) |
4 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Europium(II) silicate, also known as europium orthosilicate, is an inorganic compound of europium and silicon with the chemical formula Eu2SiO4. It is an orthosilicate containing isolated SiO4 tetrahedra and divalent europium ions. The compound is strongly luminescent and undergoes both structural and magnetic phase transitions.
Preparation
[edit]Europium(II) silicate can be prepared by reacting europium(III) oxide, elemental europium and silicon dioxide at high temperature:
- 2 Eu2O3 + 2 Eu + 3 SiO2 → 3 Eu2SiO4
Lemon-yellow single crystals have been obtained by heating the reactants in evacuated silica ampoules at 1373 K for 48 hours, followed by controlled cooling.[1]
It can also be synthesized from Eu2O3 and SiO2 under a reducing hydrogen atmosphere.[1]
Structure and properties
[edit]At room temperature, europium(II) silicate crystallizes in the monoclinic crystal system with the larnite-type structure, isotypic with β-Ca2SiO4. It belongs to space group P21/n (No. 14), with lattice parameters a = 5.6502 Å, b = 7.0915 Å, c = 9.7584 Å and β = 92.614°, with four formula units per unit cell.[1]
The structure contains isolated SiO4−4 tetrahedra, so Eu2SiO4 is a nesosilicate. Two crystallographically distinct Eu2+ sites occur in the structure.[1]
At about 452 K (179 °C), Eu2SiO4 undergoes a reversible transition to an incommensurately modulated high-temperature phase related to the orthorhombic Pnma structure. The transition is accompanied by pronounced changes in birefringence, dielectric properties and luminescence.[1]
Earlier measurements placed the transition near 165 °C and showed that it is accompanied by changes in colour, optical band gap, luminescence intensity and dielectric constant.[2]
Europium(II) silicate is strongly photoluminescent. At room temperature it emits bright yellow light, while the high-temperature phase shows a shift toward orange emission.[1]
It is also ferromagnetic at very low temperature. Modern measurements report a ferromagnetic transition below approximately 7 K.[1]
Oxidation
[edit]Europium(II) silicate is stable in air at moderate temperatures but oxidizes on stronger heating. Oxidation proceeds topotactically through intermediate europium silicate phases containing both Eu2+ and Eu3+, and ultimately yields Eu2SiO5 at high temperature.[3]
Partial oxidation begins at intermediate temperatures with formation of metastable apatite-like phases; Eu2SiO5 is observed after more extensive oxidation above about 1000 °C.[3]
Applications
[edit]Europium(II) silicate has been studied as a luminescent material because of its intense yellow Eu2+ emission and its temperature-dependent optical properties.
More recently, Eu2SiO4 has attracted interest as a low-temperature magnetocaloric material. A 2025 study reported a magnetic entropy change of 21.6 J kg−1 K−1 for a field change of 0–1 T near liquid-helium temperature, together with relatively high thermal conductivity, suggesting possible use in cryogenic magnetic refrigeration.[4]
References
[edit]- 1 2 3 4 5 6 7 Funk, Christian; Köhler, Jürgen; Lazar, Iwona; Kajewski, Dariusz; Roleder, K.; Nuss, J.; Bussmann-Holder, A.; Bamberger, H.; van Slageren, J.; Enseling, D.; Jüstel, T.; Schleid, T. (2018). "Old and New Insights into Structure and Properties of Eu2[SiO4]". Crystal Growth & Design. 18 (10): 6316–6325. doi:10.1021/acs.cgd.8b01265.
- ↑ Busch, G.; Kaldis, E.; Verreault, R.; Felsche, J. (1970). "A phase transition in Eu2SiO4". Materials Research Bulletin. 5 (1): 9–17. doi:10.1016/0025-5408(70)90068-1.
- 1 2 Felsche, J.; Kaldis, E. (1972). "Thermal oxidation of Eu2SiO4—a topotactic solid state reaction". Journal of Solid State Chemistry. 5 (1): 49–56. doi:10.1016/0022-4596(72)90008-4.
- ↑ "Ferromagnetic Eu2SiO4 Compound with a Record Low-Field Magnetocaloric Effect and Excellent Thermal Conductivity Near Liquid Helium Temperature". Journal of the American Chemical Society. 147 (17): 14684–14693. 2025. doi:10.1021/jacs.5c02997.