K3Gd3B4O12: a new member of rare-earth orthoborate for luminescent host matrix

A new member of rare-earth orthoborate K 3 Gd 3 B 4 O 12 was prepared by a flux method and structurally characterized by single-crystal structure analysis for the first time. It features a two-dimensional layer structure containing [Gd 8 (BO 3 ) 8 ] ∞ layers parallel to the ab -plane. Gd(3)O 7 groups, B(3)O 3 groups, B(4)O 3 groups and large K + ions distribute in between the[Gd 8 (BO 3 ) 8 ] ∞ layers, and bond adjacent layers. Theoretical researches by density functional theory (DFT) revealed that the compound K 3 Gd 3 B 4 O 12 is an indirect band-gap semiconductor and the optical absorption can be mainly ascribed to O→K, O→Gd and O→B charge transfers. Moreover, a series of K 3 Gd 3− x − y B 4 O 12 : x Tb 3+ , y Eu 3+ phosphors were prepared, their morphology and tunable multicolour emission properties were studied. Under UV or near-UV excitations the luminescence colours will tune from green through yellow, orange to red by simply adjusting the relative Tb 3+ and Eu 3+ concentrations.