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Published on: April 14, 2020
Dysprosium(III) Sulfate Dy2(SO4)3: Crystal and Electronic Structure, Thermal Expansion, Thermochemistry, Magnetic and
Yuriy G Denisenko1,2,3, Victor V Atuchin4,5, Maxim S Molokeev6,7,8
1Department of Inorganic and Physical Chemistry, Tyumen State University, Tyumen, Russia.
Abstract:
Dy2(SO4)3 is shown to exhibit negative thermal expansion (NTE) in all three crystallographic directions, suggesting that rare earth sulfates may serve as a novel platform for 3D NTE materials. High-temperature x-ray diffraction (453-703 K) reveals a NTE volume coefficient of αV = -18.27(7)·10-6 K-1, attributed to anisotropic compression along the b- and c-axes. Combined DFT calculations and vibrational spectroscopy identify low-frequency phonon modes with pronounced rotational motions of SO4 tetrahedra, suggesting a rigid unit mode (RUM) contribution to the lattice compression. In addition to the NTE, the material exhibits high thermal stability (onset of decomposition at 783°C), a wide band gap (Eg = 6.1 eV), narrow photoluminescence at 577 nm, suitable for Dy3+-based laser applications, and pronounced magnetic anisotropy, indicating strong crystal field effects. These results extend the known families of NTE to sulfate-based structures and position Dy2(SO4)3 as a multifunctional material combining NTE with favorable optical and magnetic properties.
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