A strategy for realizing tunable luminescence and full-color emission in Sr₃Gd₂(Si₃O₉)₂:Eu phosphors by introducing dual functional Mn²⁺

The exploration of new single-phase phosphors with tunable luminescence and full-color emission is of great importance due to their unique material properties and potential applications in the solid-state lighting field. By introducing Mn²⁺ into the SGSO:Eu system, on the one hand, the Mn²⁺ ion can act as an activator to emit green light together with the blue light corresponding to Eu²⁺ and the red light of Eu³⁺ due to the efficient energy transfer from Eu²⁺ and Gd³⁺ to Mn²⁺ and on the other hand, Mn²⁺ can also act as a structure regulator to tune the luminescence properties of Eu²⁺ and Eu³⁺ ions in the SGSO host by varying their site occupation, distribution and polyhedron distortions. As a result, the color hue of SGSO:Eu,Mn can be tuned from cyan to white and to yellow under the excitation of selective ultraviolet (UV) light. A white light-emitting diode (LED) device has been demonstrated by integrating the representative SGSO:Eu,0.09Mn with a UV LED light source, which shows a low corresponding color temperature (CCT = 4934 K), a high color rendering index (R_a = 86.6), and a CIE color coordinate (0.35, 0.34). In addition, at low Mn²⁺ concentrations, the as-prepared SGSO:Eu,Mn presents excellent thermal stability and a tiny chromaticity shift under the excitation of 274 nm light in the temperature range of 298-478 K due to the comparable thermal stability of Eu²⁺, Mn²⁺ and Eu³⁺, while at high Mn²⁺ concentrations, the SGSO:Eu,Mn shows a high temperature sensitivity (as high as 2.9% K^-1 at 298 K) excited at 350 nm due to the increased thermal stability of Eu²⁺ and the decreased thermal stability of Mn²⁺. More importantly, the approach to achieve tunable luminescence and full-color emission via incorporating the activator and structure regulator Mn²⁺ ions demonstrated in this work is not limited to the SGSO:Eu material, but applies to other phosphor material systems.