Optimizing photo- and mechanoluminescence of CaGeO3: Mn2+, Ga3+, Si4+ through synergistic B-site regulation

Manganese-doped calcium germanate was used as the model host to optimize dual-mode emission by synergistic regulation at the B site. A series of Ga 3+ -doped samples was first prepared to determine the composition with the strongest mechanoluminescence (ML) response. A small amount of Si 4+ was then introduced to recover the photoluminescence (PL) performance. The Ga 3+ /Si 4+ co-doping strategy combines defect construction with lattice rigidification. Heterovalent Ga 3+ substitution creates an oxygen-vacancy trap network, which preserves the energy-storage capability required for ML. Isovalent Si 4+ incorporation strengthens the lattice framework through highly stable Si-O bonds, thereby suppressing non-radiative relaxation of Mn 2+ and compensating for the defect-induced energy loss. Thermoluminescence (TL), Raman spectroscopy, and optical characterizations show that B-site regulation modifies both trap distribution and lattice rigidity. As a result, PL and ML are simultaneously improved. This work provides a structural-regulation strategy for designing multimodal luminescent materials.