Mn²⁺ luminescence of Gd(Zn,Mg)B₅O₁₀ pentaborate under high pressure

The results of X-ray diffraction studies of the Gd(Mg_0.95-x,Zn_xMn_-0.05)B₅O₁₀ down-converting phosphor as a function of Mg-Zn composition are presented. The lattice parameters and unit cell volumes of GdMg_0.95-xZn_xMn_0.05B₅O₁₀ pentaborates are examined. The relationships between the structure and optical properties of these materials are explicated based on the results of theoretical calculations of the energy structure. The effect of pressure on the luminescence of Mn²⁺ in this system was studied up to ca. 32 GPa. The observed quenching of Mn²⁺ luminescence is due to the crossing of the emitting ⁴T_1g level with the non-emitting ²T_2g state. This crossing sets a long-wavelength limit on the possibility of observing the emission of Mn²⁺ ions, which is around 850 nm.