Synthesis and characterization of manganese-doped zinc orthosilicate phosphor powders

Homogeneous and nanocrystalline manganese-doped zinc orthosilicate (Zn2SiO4:Mn) phosphor powders were prepared using a sol–gel process by controlling the hydrolysis of silicon alkoxide and zinc chloride precursors. The Mn dopant content influenced the gelation rate, homogeneity, degree of agglomeration, and luminescence of powders. Mn-doped xerogel powders were amorphous and crystallized into pure willemite (α-Zn2SiO4) structure when heated to 600 °C. After heating at 800–1000 °C, the crystallite sizes of Zn2−xMnxSiO4 phosphor powders were around 15–32 nm at an Mn doping level of x = 0.2–20 mol%. The resulting powder phosphors exhibited prominent photoluminescence emission peaks centered at 520–529 nm, depending on the doping content. The intensity of the green emission was strongly related to the dopant content and improved crystallinity. Furthermore, reducing the specific surface area and pore volume further enhanced the luminous efficiency of willemite powders. The sol–gel transition, crystallinity, microstructure, and luminescent property of phosphor powders were investigated.