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

A new member of rare-earth orthoborate KGdBO 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(BO)] layers parallel to the ab-plane. Gd(3)O groups, B(3)O groups, B(4)O groups and large K ions distribute in between the[Gd(BO)] layers, and bond adjacent layers. Theoretical researches by density functional theory (DFT) revealed that the compound KGdBO 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 KGdBO:xTb, yEu 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 and Eu concentrations.