Long-lasting phosphorescence in Mn~(2+): Zn_2GeO_4 crystallites precipitated in transparent GeO_2-B_2O_3-ZnO glass-ceramics

摘要

Mn~(2+)-doped GeO_2-B_2O_3-ZnO (GBZ) glasses were investigated and developed as long-lasting phosphorescence host materials. Transparent glass-ceramics were obtained after heat-treated at the first crystallization temperature for 20 min. By X-ray diffraction measurement and SEM observation, it is clarified that Zn_2GeO_4 crystallites with a diameter of about 1 μm precipitate on the sample's surface after heat-treatment. An orange long-lasting phosphorescence from Mn~(2+) was observed in the 25GeO_2-25B_2O_3-50ZnO glass matrix, however, a stronger long-lasting green phosphorescence was observed in the phase of Zn_2GeO_4 crystallites. This phenomenon is considered to be due to the different ligand field environment surrounding Mn~(2+) ions in the glass and the glass-ceramics. A possible mechanism for the long-lasting phosphorescence in the Mn~(2+)-doped glass was discussed.