Synthesis, color-tunable emission, thermal stability, luminescence and energy transfer of Sm3+ and Eu3+ single-doped M3Tb(BO3)3 (M = Sr and Ba) phosphors

Abstract

A series of new tunable emission phosphors of Sm³⁺ and Eu³⁺ single-doped M₃Tb(BO₃)₃ (M = Sr and Ba) phosphors were synthesized by the solid-state reaction. Crystallization behavior and structure, reflectance spectral properties, luminescence properties, energy transfer, lifetimes, temperature-dependent luminescence properties and CIE chromaticity coordinate of M₃Tb(BO₃)₃:Ln³⁺ (M = Sr and Ba, Ln = Sm and Eu) were systematically investigated. M₃Tb(BO₃)₃ (M = Sr and Ba) crystallizes in a rhombohedral cell with space group R by Rietveld structure refinement of the obtained phosphors with the standard data of Ba₃Dy(BO₃)₃. Sr₃Tb(BO₃)₃ and Ba₃Tb(BO₃)₃ emit yellowish-green emission with the main peak around 555 and 550 nm, respectively, which originates from the ⁵D₄ → ⁷F₄ transition of Tb³⁺, and M₃Tb(BO₃)₃:Ln³⁺ (Ln = Sm and Eu) phosphors show intense yellowish-green, yellow, orange and red emission with increasing Ln³⁺ concentration under 274 and 286 nm excitation. The orange-red/red emissions show peak maxima at 613 nm (Sr₃Tb(BO₃)₃:Sm³⁺), 627 nm (Sr₃Tb(BO₃)₃:Eu³⁺), 607 nm (Ba₃Tb(BO₃)₃:Sm³⁺) and 625 nm (Ba₃Tb(BO₃)₃:Eu³⁺), and are due to the efficient energy transfer of Tb³⁺–Sm³⁺ and Tb³⁺–Eu³⁺. The temperature-dependent luminescence properties of M₃Tb(BO₃)₃:Ln³⁺ are characterised by good thermal stabilities up to 150 °C, up to 72.8%. However, due to the defect in the host of the Sr₃Tb_0.99(BO₃)₃:0.01Sm³⁺ phosphor, an amazing and interesting phenomenon can be observed that the emission intensity is enhanced constantly with increasing temperature.