“…This weak-field scheme occurs where Eu 2+ ion is substituted for larger cations at highly coordinated sites surrounded by small and highly charged cations. 50 Some examples of this type of phosphors (type Eu2-A) are: Ba 2 Mg 3 F 10 :Eu 2+ , 51 BaMg(SO 4 ) 2 :Eu 2+ , 52 BaY 2 F 8 :Eu 2+ , 53 Be 2 MSi 2 O 7 (M = Sr, Ba):Eu 2+ , 54 KMgF 3 :Eu 2+ , 55 LiBaF 3 :Eu 2+ , 37,56 LiMgPO 4 :Eu 2+ , 57 MM'AlF 7 :Eu 2+ (M, M' = Ca, Sr, Ba), 58 MFCl (M = Sr, Ba):Eu 2+ , 59 MFX (M = Sr, Ba; X = Cl, Br):Eu 2+ , 60 MSO 4 :Eu 2+ (M = Ca, Sr, Ba), 61 SrAlF 5 :Eu 2+ , 62 SrAl 12 O 19 :Eu 2+ , 63,64 SrB 4 O 7 :Eu 2+ , 65,66 and RbMgF 3 :Eu 2+ . 67 The weak crystal-field splitting scheme for the electronic energy levels in Eu 2+ ion is schematically shown in Fig.…”