Unexpected Coexisting Solid Solutions in the Quasi‐Binary Ag^(II)F₂/Cu^(II)F₂ Phase Diagram**

Abstract

High‐temperature solid‐state reaction between orthorhombic AgF2 and monoclinic CuF2 (y=0.15, 0.3, 0.4, 0.5) in a fluorine atmosphere resulted in coexisting solid solutions of Cu‐poor orthorhombic and Cu‐rich monoclinic phases with stoichiometry Ag1−xCuxF2. Based on X‐ray powder diffraction analyses, the mutual solubility in the orthorhombic phase (AgF2 : Cu) appears to be at an upper limit of Cu concentration of 30 mol % (Ag0.7Cu0.3F2), while the monoclinic phase (CuF2 : Ag) can form a nearly stoichiometric Cu : Ag=1 : 1 solid solution (Cu0.56Ag0.44F2), preserving the CuF2 crystal structure. Experimental data and DFT calculations showed that AgF2 : Cu and CuF2 : Ag solid solutions deviate from the classical Vegard's law. Magnetic measurements of Ag1−xCuxF2 showed that the Néel temperature (TN) decreases with increasing Cu content in both phases. Likewise, theoretical DFT+U calculations for Ag1−xCuxF2 showed that the progressive substitution of Ag by Cu decreases the magnetic interaction strength |J2D| in both structures. Electrical conductivity measurements of Ag0.85Cu0.15F2 showed a modest increase in specific ionic conductivity (3.71 ⋅ 10−13±2.6 ⋅ 10−15 S/cm) as compared to pure AgF2 (1.85 ⋅ 10−13±1.2 ⋅ 10−15 S/cm), indicating the formation of a vacancy‐ or F adatom‐free metal difluoride sample.

Application of Silver Compounds in Fluoroorganic Synthesis: A Minireview

“…Use of mixed metal AgÀ Cu systems, such as Ag 1-x Cu x SO 4 [209] and Ag 1-x Cu x F 2 , [210,211] or of mixed-valence compounds such as Ag 3 (SbF 6 ) 4 [212] or Ag 3 (SO 3 F) 4 , [213] constitutes a virtually unchartered territory of organic and organofluorine chemistry. They could contribute to natural expansion of the range of possible strongly oxidizing reagents in organofluorine chemistry, in some ways similar to AgSO 4 , with additional reactivity is selected cases (e. g. introduction of SO 3 F group etc.…”