In Situ Neutron Diffraction Studies of LiCe(WO₄)₂ Polymorphs: Phase Transition and Structure–Property Correlation

Abstract

Polymorphs of LiCe­(WO4)2 [α-LiCe­(WO4)2 and β-LiCe­(WO4)2] were successfully synthesized by a citric acid-assisted sol–gel method for the first time. Phase purity and crystallinity were confirmed by powder X-ray diffraction and further characterized by X-ray photoelectron spectroscopy, field emission scanning electron microscopy, Raman, and thermogravimetric–differential thermal analysis measurements. Investigation of the effect of calcination temperature and time indicated the existence of an irreversible structural phase transition from low-temperature (LT) β-phase to high-temperature (HT) α-phase, which is systematically followed by in situ HT powder neutron diffraction (NPD) studies. Rietveld refinements using NPD data revealed that α-LiCe­(WO4)2 crystallizes in tetragonal Scheelite-type structure (I41/a), while β-LiCe­(WO4)2 crystallizes in triclinic α-LiPr­(WO4)2-type structure (P1̅). Furthermore, β-LiCe­(WO4)2 undergoes a reconstructive phase transition where WO6 of the β-phase rearranges to WO4 at HT in α-phase and is supported by Raman measurements. Anodic redox activities of these polymorphs were determined by cyclic voltammetry and galvanostatic charge–discharge measurements. Interestingly, β-phase has shown promising results compared with that of α-phase, which is attributed to the easy Li-ion diffusion in between the parallel layers of WO6 and also to the greater structural stability of the β-phase. Thus, our initial understanding on the structure–property of these LiCe­(WO4)2 polymorphs provides insights into the design of new insertion anode electrodes for Li-ion batteries.

Hydrothermal synthesis of defect-induced pristine α-NaCe(WO4)2: a novel material for solid state lighting and gas sensing

“…The low lattice parameters, unit cell volumes, Na–O and Ce–O bond lengths, Na–O–W, Ce–O–W and O–W–O bond angles of NCWO 120°C are attributed to distortions within the CeO 8 polyhedra and WO 6 octahedra induced by oxygen vacancies (V O ). 10 Very briefly, we have evaluated the degree of CeO 8 polyhedron distortion ( K ) to be ∼0.96, 0.93 for NCWO 120°C and NCWO 140°C , respectively, using the relation where d 1 (Ce–O) and d 2 (Ce–O) denote two different bond lengths. The WO 6 octahedron distortion ( N ) was found to be ∼0.86 and 0.79 for NCWO 120°C and NCWO 140°C , respectively, using the relation where α 1 (O–W–O) and α 2 (O–W–O) represent two different bond angles.…”

Controllable crystal form transformation and temperature sensing properties studies of K3Sc0.5Lu0.5F6: Ho3+, Yb3+ with cryolite structure

“…Therefore, a better understanding of the crystal structure or phase transition of rare-earth cryolite luminescent materials is conducive to regulating their luminescence properties, which is of great significance for molecular design, new material synthesis and expanding the application field of materials. 43,44 So far, the optical properties of rare-earth ion-doped cryolite-type materials under different synthesis conditions is a problem that needs further study. As far as we know, the luminescence properties of Ho 3+ , Yb 3+ co-doped KSLF have not been observed, and the luminescence properties of Ho 3+ , Yb 3+ doped cubic and monoclinic KSLF have not been compared.…”

“…The specific crystal phase has own luminescence properties. Therefore, a better understanding of the crystal structure or phase transition of rare‐earth cryolite luminescent materials is conducive to regulating their luminescence properties, which is of great significance for molecular design, new material synthesis and expanding the application field of materials 43,44 . So far, the optical properties of rare‐earth ion‐doped cryolite‐type materials under different synthesis conditions is a problem that needs further study.…”

Antiferromagnetism of Double Molybdate LiFe(MoO4)2

“…The combinations of three categories of metal ions make this family full of varieties in physics and functionality. The inclusion of Li ion at A site make them suitable to be used in lithium-ion batteries as anode materials, while the W/Mo can provide a relative large spin-orbit coupling considering its 4d/5d orbitals 1,[6][7][8][9] . Most importantly, the B-site ions with narrow bands can provide other applicable physical properties, such as magnetism and luminescence [10][11][12][13][14][15] .…”

“…Double tungstates and molybdates with the chemical formula A I B III (MO 4 ) 2 form a big family of transition metal oxides, where A is an alkali metal; B is a trivalent cation such as Bi 3+ , In 3+ , or Fe 3+ or a rare earth, Sm 3+ or Eu 3+ ; and M represents W 6+ or Mo 6+ . − The combinations of three categories of metal ions make this family full of varieties in physics and functionality. The inclusion of the Li ion at A site makes them suitable to be used in lithium-ion batteries as anode materials, while the W/Mo can provide a relative large spin–orbit coupling considering its 4d/5d orbitals. ,− Most importantly, the B-site ions with narrow bands can provide other applicable physical properties, such as magnetism and luminescence. − …”