Syntheses and optical properties of α- and β-Zn2SiO4: Mn nanoparticles by solvothermal method in ethylene glycol–water system

Mn doped Zn2SiO4 phosphors (Zn2SiO4:Mn) with different morphologies and crystal structures, exhibiting different luminescence, were synthesized via a low-temperature solvothermal method in ethylene glycol–water system. Powder X-ray (XRD) and scanning electron microscopy (SEM) were used to characterize the phase purity, particle size and morphology. Photoluminescence (PL) spectra were collected and analyzed. The usual α-phase Zn2SiO4:Mn exhibited green emission centered at about 525 nm while the yellow emission centered at 563 nm resulted from β-phase Zn2SiO4:Mn. In situ XRD measurement results showed that the phase transfers from yellow to green phosphor at high temperature. The dependence of the emission intensity on the Mn2+ doping concentration was also investigated, showing that the optimum doping concentrations were relatively low. XPS analysis revealed the red shifts for both Mn 2p3/2 and Zn 2p3/2 binding energies in yellow phosphor. The shifts might indicate Zn2+ and doped Mn2+ ions in β-Zn2SiO4:Mn adopt different coordination environments from tetrahedral case that is adopted in α-Zn2SiO4:Mn.