Luminescent properties of hydrothermally prepared zinc silicate phosphors

Mn substituted willemite Zn2SiO4:Mn2+ phosphor is traditionally used in low refresh rate display technology. This phosphor shows high quantum efficiency, high luminance and purer green color than other green phosphors such as Tb3+-activated phosphates and aluminates. The long lifetime of the phosphor limits its use in the display that needs a rapid change in its image.; In this research, the decay properties of Zn silicate phosphor were investigated by a new experimental technique. Hydrothermal reactions were carried out at high temperatures to synthesize pure and dopant-containing Zn2SiO 4:Mn2+ phosphors. The dopants include the ion pairs of Ga3+ + Li+ and Al3+ + Li +.; High emission intensity was obtained at 700°C under hydrothermal conditions for the pure and dopant-containing phosphors.; For the pure Zn2SiO4:Mn2+ phosphor, the decay properties at low Mn contents were investigated. The intrinsic decay time t1/e (the decay time to the 1/e emission point) is about 13 ms at room temperature. The influence of the Mn content on the decay time t10 was studied. The Mn distribution in each single particle and among particles was adjusted by the solid/water ratio and the reactivity of ZnO. Mode emission wavelength was measured to determine the Mn concentration in the emission layer of phosphor particles. The results show that the decay time t10 of an isolated Mn2+ ion pair is not less than 15 ms. Fast decay rate is attributed to the formation of Mn clusters in willemite structure.; For the phosphors with dopants, the dopants (Ga + Li; Al + Li) do not influence the decay time t10 at 11 ms or below. The solubility of (Ga + Li) in Zn silicate willemite phase at 700°C is estimated to be 1.5--2atm% of the Zn couples, or 3--4atm% of the Zn sites can be occupied by the Ga + Li ion couples. About 4--5atm% of Zn sites can be occupied by Al + Li ion couples at 700°C. The addition of the Al + Li ion couples promotes the quantum efficiency in the VUV range, that is, from 120 to 200 nm.