On New Alkaline‐Earth Hexafluorogermanates as Host Structures for UV Phosphors

Two new hexafluorogermanate dihydrates, viz. SrGeF 6  ⋅ 2H 2 O and CaGeF 6  ⋅ 2H 2 O, were synthesised from aqueous solutions; their crystal structures were refined in space group P 2 1 / n (SrGeF 6  ⋅ 2H 2 O: a =5.9605(2) Å, b =9.6428(3) Å, a =10.9866(3) Å and β =99.1590(10), Z =4, 5122 refl., 104 param., R 1 =0.0195, w R 2 =0.0470; CaGeF 6  ⋅ 2H 2 O: a =5.8472(5) Å, b =10.5099(9) Å, c =9.6267(9) Å and β =103.521(3), Z =4, 4756 refl., 101 param., R 1 =0.0224, w R 2 =0.0616). Upon doping with Eu 2+ luminescence in the NUV regime was observed. The crystal structures of CaGeF 6 and MgGeF 6 could be solved and refined via Rietveld refinement from powder samples gained by thermal decomposition of the respective hydrates; both compounds adopt the LiSbF 6 structure type (CaGeF 6 : a =5.4099(5) Å, c =13.9835(13) Å, Z =3, R wp =0.0291, R Bragg =0.0142; MgGeF 6 : a =5.1219(2) Å, c =13.0851(7), Z =3, R wp =0.034, R Bragg =0.01). Further, the luminescence of MgGeF 6  ⋅ 6H 2 O:Eu 2+ , which emits light in the violet to blue regime, is reported.