Remarkable role of lanthanide substitution on luminescence chromaticity and thermostability of Sm3+-activated tellurate phosphors synthesized via microwave-assisted method

Abstract

Trivalent samarium-activated inorganic phosphors have held promise in optoelectronic field. Nevertheless, the troubles of low synthesis efficiency and weak luminescence performance limit their practical utilizations. Herein, a lanthanide substitution strategy is employed to construct NaLnTe₂O₇:Sm³⁺ (Ln = Y, Gd) phosphors by microwave-assisted one-step solid-state reaction. The Sm³⁺ concentration and temperature-related luminescence quenching mechanisms are investigated thoroughly. Under 405 nm excitation, the orange-red emitting behavior is controlled by the ⁴G_5/2→⁶H_7/2 (607 nm) transition. Excitingly, the whole substitution of Gd³⁺ for Y³⁺ plays a remarkable role on the improvement of luminescence chromaticity and thermostability. For the optimized NaGdTe₂O₇:3 %Sm³⁺ phosphor, at 423 K, the emissive intensity can maintain 83 % of the beginning level, which is attributed to large band gap, good structural rigidity and appropriate charge transfer band. This study illustrates a successful case of improving optical properties via chemical substitution, obtaining a promising Sm³⁺-activated tellurate phosphor for solid-state lighting.