Solvothermal synthesis of Zn ₂GeO ₄:Mn ² nanophosphor in water/diethylene glycol system

The influence of aging of the suspension containing the amorphous precusors on structural, compositional and photoluminescent properties is studied to understand the mechanism on the formation of Zn ₂GeO ₄:Mn ² nanoparticles during the solvothermal reaction in the water/diethylene glycol mixed solvent. Aging at 200 °C for 20 min forms the crystalline Zn ₂GeO ₄ nanorods and then they grow up to ∼ 50 nm in mean length after aging for 240 min. Their interplanar spacing of (410) increases with increasing the aging time. The photoluminescence intensity corresponding to the d-d transition of Mn ² increases with increasing the aging time up to 120 min, and then decreases after aging for 240 min. The photoluminescence lifetime decreases with increasing the aging time, indicating the locally concentrated Mn ² ions. These results reveal that Mn ² ions gradually replace Zn ² ions near surface through repeating dissolusion and precipitation processes during prolonged aging after the complete crystallization of Zn ₂GeO ₄.