Help Privacy Policy Disclaimer
  Advanced SearchBrowse




Journal Article

New Li-Mg phosphates with 3D framework : experimental and ab initio calculations


Tarakina,  Nadezda V.
Nadezda V. Tarakina, Kolloidchemie, Max Planck Institute of Colloids and Interfaces, Max Planck Society;

External Resource
No external resources are shared
Fulltext (restricted access)
There are currently no full texts shared for your IP range.
Fulltext (public)
There are no public fulltexts stored in PuRe
Supplementary Material (public)
There is no public supplementary material available

Kellerman, D. G., Tyutyunnik, A. P., Medvedeva, N. I., Chufarov, A. Y., Fortes, A. D., Gibbs, A., et al. (2020). New Li-Mg phosphates with 3D framework: experimental and ab initio calculations. Dalton Transactions, 49(29), 10069-10083. doi:10.1039/D0DT01963A.

Cite as: https://hdl.handle.net/21.11116/0000-0006-AA9C-B
Two new lithium-magnesium phosphates LiMg6(PO4)3(P2O7) and
Li(Mg5.62Sc0.19Li0.19)(PO4)3(P2O7) were synthesized by the solid-phase method. Using high-resolution
time-of-flight neutron powder diffraction (TOF NPD) and X-ray powder diffraction (XRPD), we
established that these phosphates have Pnma orthorhombic structure with the cell parameters
a=9.14664(5) Å, b=18.83773(8) Å, c=8.27450(4) Å, V=1425.71(1) Å3 and a=9.14516(5) Å,
b=18.84222(9) Å, c= 8.28204(4) Å, V=1427.12(1) Å3, respectively. The crystal structures can be
described by stacking of the [Mg6O18] or [Mg5.62Sc0.19Li0.19O18] wavy layers, which are parallel to the
(100) direction and interconnected through PO4 tetrahedra and P2O7 groups to a 3D-framework. Li atoms
are located in large tunnels formed in a 3D lattice, which contributes to lithium diffusion. AC impedance
spectroscopy shows that LiMg6(PO4)3(P2O7) and Li(Mg5.62Sc0.19Li0.19)(PO4)3(P2O7) have Li ion
conductivity of 3.6 10-4 S/cm and 1.7 10-4 S/cm at 950 °C, with activation energy of 1.28 eV and
1.55 eV, respectively. NMR MAS studies confirmed a coexistence of pyro- and orthogroups in the
structure of both phases and two lithium positions in Li(Mg5.62Sc0.19Li0.19)(PO4)3(P2O7). The first-
principles method was used to study the electronic structure and stability of the two phases. The
calculated formation enthalpies demonstrated that Sc is a stabilizing impurity in LiMg6(PO4)3(P2O7),
while there exists a strong destabilization of olivine LiMgPO4 upon doping with Sc. This explains the
failure to synthesize the Sc-doped olivine. The new phosphate LiMg6(PO4)3(P2O7) is a dielectric with
band gap of 5.35 eV, which decreases to 4.85 eV due to a localized Sc 3d peak upon doping with Sc.
These findings are consistent with the results obtained from UV-Vis spectroscopy. The new phase may be
a good optical matrix similar to LiMgPO4.