TY - JOUR
T1 - Thermochemistry of 3D and 2D Rare Earth Oxychlorides (REOCls)
AU - Yang, Shuhao
AU - Anderko, Andrzej
AU - Riman, Richard E.
AU - Navrotsky, Alexandra
N1 - Funding Information:
The authors acknowledge the use of facilities within the Eyring Materials Center supported in part by NNCI-ECCS-2025490 at Arizona State University. This work was supported by the US Department of Energy Critical Materials Institute (CMI) Hub under the Subaward Number DE-AC02-07CH11358. We thank Douglas Daniel for help with Raman spectroscopy experiments.
Funding Information:
This work was supported by the US Department of Energy Critical Materials Institute (CMI) Hub under the Subaward Number DE-AC02-07CH11358.
Publisher Copyright:
© 2022 American Chemical Society.
PY - 2022
Y1 - 2022
N2 - The thermodynamic stability of rare earth (RE) materials plays a key role in the design of separation and recycling processes for RE elements. Thermodynamic stability is fundamentally influenced by the lanthanide contraction, as observed in the systematic reduction of unit cell volumes with increasing atomic number. RE materials are found in the form of solids having primary bonds in three dimensions (3D materials) as well as ones with primary bonds in two dimensions (2D materials) whose layers are held together by weak van der Waals (vdW) forces. While studies of synthesis, structure, and physical properties of 2D RE materials are numerous, no systematic research has compared their thermodynamic stability to that of 3D materials. In the present work, RE oxychlorides (REOCls), which display a structural transition from a 3D-polyhedral network (PbFCl-type) to a vdW-bonded layered one (SmSI-type) as the RE size decreases, were all synthesized by the flux method. High-temperature oxide melt solution calorimetry was used to determine their formation enthalpies to enable Born-Haber cycles to calculate lattice energies. Our results indicate that REOCl compounds are thermodynamically stable when compared to their binary oxides and chlorides. The lattice energies of 3D REOCls increase with decreasing RE size yet are insensitive to unit cell volumes for 2D REOCls. This is caused by interatomic interactions parallel and perpendicular to layers in the SmSI-type REOCls, causing a different structure response to the lanthanide contraction than 3D RE materials.
AB - The thermodynamic stability of rare earth (RE) materials plays a key role in the design of separation and recycling processes for RE elements. Thermodynamic stability is fundamentally influenced by the lanthanide contraction, as observed in the systematic reduction of unit cell volumes with increasing atomic number. RE materials are found in the form of solids having primary bonds in three dimensions (3D materials) as well as ones with primary bonds in two dimensions (2D materials) whose layers are held together by weak van der Waals (vdW) forces. While studies of synthesis, structure, and physical properties of 2D RE materials are numerous, no systematic research has compared their thermodynamic stability to that of 3D materials. In the present work, RE oxychlorides (REOCls), which display a structural transition from a 3D-polyhedral network (PbFCl-type) to a vdW-bonded layered one (SmSI-type) as the RE size decreases, were all synthesized by the flux method. High-temperature oxide melt solution calorimetry was used to determine their formation enthalpies to enable Born-Haber cycles to calculate lattice energies. Our results indicate that REOCl compounds are thermodynamically stable when compared to their binary oxides and chlorides. The lattice energies of 3D REOCls increase with decreasing RE size yet are insensitive to unit cell volumes for 2D REOCls. This is caused by interatomic interactions parallel and perpendicular to layers in the SmSI-type REOCls, causing a different structure response to the lanthanide contraction than 3D RE materials.
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U2 - 10.1021/acs.inorgchem.2c00763
DO - 10.1021/acs.inorgchem.2c00763
M3 - Article
C2 - 35486112
AN - SCOPUS:85129937823
SN - 0020-1669
JO - Inorganic chemistry
JF - Inorganic chemistry
ER -