Phosphorescence in Mn4+-Doped R +/R 2+ Germanates (R + = Na+ or K+, R 2+ = Sr2+)

Single crystals of three new compounds, Na_0.36Sr_0.82Ge₄O₉ (1, proposed composition), Na₂SrGe₆O₁₄ (2), and K₂SrGe₈O₁₈ (3), were obtained and characterized using single-crystal X-ray diffraction. Their structures contain three-dimensional (3D) anionic frameworks built from GeO₄ and GeO₆ polyhedra. The presence of octahedral Ge⁴⁺ sites makes the new phases suitable for Mn⁴⁺ substitution to obtain red-emitting phosphors with a potential application …