title: Multiple Fluorine-Substituted Phosphate Germanium Fluorides and Their Thermal Stabilities.
abstract: Anhydrous compounds are crucially important for many technological applications, such as achieving high performance in lithium/sodium cells, but are often challenging to synthesize under hydrothermal conditions. Herein we report that a modified solvo-/hydro-fluorothermal method with fluoride-rich and water-deficient condition is highly effective for synthesizing anhydrous compounds by the replacement of hydroxyl groups and water molecules with fluorine. Two anhydrous phosphate germanium fluorides, namely, Na3[GeF4(PO4)] and K4[Ge2F9(PO4)], with chainlike structures involving multiple fluorine substitutions, were synthesized using the modified solvo-/hydro-fluorothermal method. The crystal structure of Na3[GeF4(PO4)] is constructed by the common single chains∞1{[GeF4(PO4)]3-} built from alternating GeO2F4octahedra and PO4tetrahedra. For K4[Ge2F9(PO4)], it takes the same single chain in Na3[GeF4(PO4)] as the backbone but has additional flanking GeOF5octahedra via an O-corner of the PO4groups, resulting in a dendrite zigzag single chain∞1{[Ge2F9(PO4)]4-}. The multiple fluorine substitutions in these compounds not only force them to adopt the low-dimensional structures because of the "tailor effect" but also improve their thermal stabilities. The thermal behavior of Na3[GeF4(PO4)] was investigated by an in situ powder X-ray diffraction experiment from room temperature to 700 °C. The modified solvo-/hydro-fluorothermal method is also shown to be effective in producing the most germanium-rich compounds in the germanophosphate system.
authors.affiliation: Fujian Provincial Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, College of Materials, Xiamen University , Xiamen 361005, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Huang
authors.affiliation: Fujian Provincial Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, College of Materials, Xiamen University , Xiamen 361005, China.
authors.forename: Biao
authors.initials: B
authors.lastname: Liu
authors.affiliation: Xiamen Zijin Mining and Metallurgy Technology Co Ltd , Xiamen 361101, China.
authors.forename: Rong-Chuan
authors.initials: RC
authors.lastname: Zhuang
authors.affiliation: Department of Geological Sciences, University of Saskatchewan , 114 Science Place, Saskatoon, SK S7N5E2, Canada.
authors.forename: Yuanming
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Fujian Provincial Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, College of Materials, Xiamen University , Xiamen 361005, China.
authors.forename: Jin-Xiao
authors.initials: JX
authors.lastname: Mi
authors.affiliation: Fujian Provincial Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, College of Materials, Xiamen University , Xiamen 361005, China.
authors.forename: Ya-Xi
authors.initials: YX
authors.lastname: Huang