Tb3+- and Yb3+-doped novel KBaLu(MoO4)3 crystals with disordered chained structure showing down- and up-conversion luminescence

Abstract

In this study, a novel dual-mode luminescence phosphor KBaLu(MoO₄)₃:Tb³⁺,Yb³⁺ has been synthesized by high-temperature solid-state reactions, and the crystal structures have been determined for the first time. Single-crystal X-ray diffraction data reveal that its space groups are C2/c. The crystalline structure is constituted by K/BaO₈ distorted square antiprisms, distorted LuO₈ polyhedra and two kinds of distorted MoO₄ tetrahedra, which form chains lying along the c-axis. Spectroscopic properties and energy transfer mechanisms are investigated by detailed analyses of emission and excitation spectra and excited-state lifetimes. The KBaLu(MoO₄)₃:Tb³⁺,Yb³⁺ phosphor shows dominant green emissions in the visible region, which are due to ⁵D₄ → ⁷F₅ transition of Tb³⁺ under excitation light in ultraviolet region as well as a 980 nm laser, and the CIE coordinates are close to the Society of Motion Picture and Television Engineers (SMPTE) standard values for primary green (0.310, 0.595). With the increasing temperature, the luminescence of KBaLu(MoO₄)₃:Tb³⁺,Yb³⁺ phosphor decreases almost linearly with the CIE coordinate variation from (0.326, 0.616) to (0.327, 0.530), which results in photoluminescence color variation from primary green to yellowish-green. The present results demonstrate the successful synthesis of a dual-mode luminescence material KBaLu(MoO₄)₃:Tb³⁺,Yb³⁺ phosphor with both up- and down-conversion luminescence properties; moreover, it can be used as a potential spectrum converter in display lighting and anti-counterfeiting.