Crystallization‐induced valence state change of Mn2+ → Mn4+ in LiNaGe4O9 glass‐ceramics

Abstract Tetra‐valent manganese (Mn 4+ ) has been regarded as an efficient non‐rare‐earth red‐light emitting ion, which has stimulated continued search of robust hosts and efficient synthetic methods to stabilize Mn 4+ centers with strong photoluminescence. In this work, we demonstrate a facile synthetic method for Mn 4+ doped glass‐ceramic (GC) based on crystallization‐induced oxidation state change in an oxide glass. The parent glass with a formula of LiNaGe 4 O 9 is fabricated by melt‐quenching and crystallization is induced by thermal treatment in air. Oxidation of Mn 2+ in glass to Mn 4+ in the GC is confirmed by both optical spectroscopy and electron paramagnetic resonance (EPR) measurements. After thermal treatment, the characteristic reddish photoluminescence (PL) of Mn 2+ in the glass centered at 611 nm disappears and a strong photoluminescence peak at 660 nm attributed to Mn 4+ is observed. The conversion to Mn 4+ after crystallization in the examined system may have strong implications for synthesis of Mn 4+ doped phosphors which always requires rigorous control of the redox equilibrium during synthesis.