New Insights into Alkali Metal Tungstates: The High Temperature Polymorphism of Na2WO4, the New Polymorph Li2WO4‐V and the Redetermined Crystal Structure of Li2W2O7. Issue 10 (14th February 2022)

• Record Type: Journal Article
• Authors: Hämmer, Matthias; Höppe, Henning A.
• Is Part Of: Zeitschrift für anorganische und allgemeine Chemie. Volume 648:Issue 10(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-14
• Subjects: tungstates -- alkaline metal -- crystal structure -- thermal analysis -- polymorphism; Chemistry, Inorganic -- Periodicals; Chemistry -- Periodicals; 540
• DOI: 10.1002/zaac.202100373
• Languages: English
• ISSNs: 0044-2313

Abstract

Abstract: Trimorphous temperature‐dependent polymorphism (I: above 591°C, II: 589‐591°C, III: below 589°C) was confirmed for sodium tungstate Na2 WO4 using DSC and temperature‐programmed powder XRD. Na2 WO4 ‐I crystallises in space group Fddd (no. 70, a =650.28(1), b =1285.12(3), c =1105.26(2) pm, 63 rparam., R Bragg = 0.008), for Na2 WO4 ‐II a unit cell is suggested. Moreover, the crystal structure of the new triclinic polymorph Li2 WO4 ‐V prepared employing a LiF flux was elucidated in space group P 1 ‾ (no. 2, a =527.45(2), b =777.69(3), c =797.31(3) pm, α =105.835(2), β =103.391(2), γ =90.581(2)°, 1080 irefl., 100 param., w R 2 =0.063). Finally, the crystal structure of Li2 W2 O7 crystallising in space group P 1 ‾ (no. 2, a =505.57(1), b =705.00(2), c =829.03(2) pm, α =69.646(1), β =77.868(1), γ =77.868(1)°, 2386 refl., 105 param., w R 2 =0.025) was redetermined revealing yet unreported lithium disorder yielding new insights into its high ionic conductivity. Abstract :