Substitution disorder and photoluminescent property of a new rare-earth borate: K₃TbB₆O₁₂

Abstract A new rare-earth borate K3TbB6O12 has been prepared using the high temperature molten salt method and was structurally determined by single crystal X-ray diffraction analyses. The structure features a three-dimensional (3D) framework which is composed of isolated B5O10, KO6, KO8 and TbO6 groups. An atom site in the 32 screw axis is shared by K and Tb atoms with the molar ratio of 1:1. The self-activated photoluminescence (PL) property of K3TbB6O12 was studied. Under the excitation of 378 nm, the emission spectrum exhibits an intense green emission centered at 543–548 nm with the chromaticity coordinates (0.342, 0.590), which can be assigned to the 5D4→7F5 transition of Tb3+. The excitation spectra cover a wide range from 330 to 385 nm, which suggests that the K3TbB6O12 phosphors can be effectively excited by a near-UV light source. One may expect that compound K3TbB6O12 can be used as a green phosphor pumped by near-UV LED chips.