Optical properties of Cr3+ ion in lithium metasilicate Li2O · SiO2 transparent glass-ceramics

The optical properties of Cr3+ ions in lithium metasilicate (Li2O · SiO2) transparent glass-ceramics were investigated. The main crystalline phase precipitated was the lithium metasilicate (Li2O · SiO2) crystal. The percent crystallinity and crystalline size were ranging 65-75% and 20-35 nm, respectively. The color changes drastically to deep pink from emerald green upon crystallization. New and strong absorption bands appeared and the absorption intensity increases by about 10 times that in glass. These new absorption bands are found to be derived from Cr3+ ions in octahedral sites in the lithium metasilicate crystal lattice. Cr3+ ions substitute for three Li+ ions and occupy the distorted octahedral site between single [SiO4]n chains of lithium metasilicate crystal. The ligand field parameters can be estimated: 10Dq = 13 088 cm−1, B = 453 cm−1, Dq/B = 2.89 and C = 2036 cm−1. The near-infrared luminescence centered at 1250 nm was not detected in the deep pink glass-ceramics unlike emerald green glass.