Effects of starting compositions on the phase equilibrium in hydrothermal synthesis of Zn2SiO4:Mn2+

The hydrothermal technique is one of the wet-chemical methods to produce phosphor for display applications. In this study Mn-doped Zn2SiO4 phosphors were hydrothermally synthesized using ZnO and SiO2. When the composition of the raw materials was consistent with the stoichiometry of Zn2SiO4, hemimorphite (Zn4Si2O7(OH)(2).H2O) phase formed under the condition of low temperature and pressure. The phase transition from Zn4Si2O7(OH)(2).H2O to Zn2SiO4 occurred at 350similar to360degreesC under an external pressure of 140MPa. However, it was found that the Zn2SiO4 phase could be precipitated at low temperature by adjusting the composition of raw materials. Investigation of actual doping concentrations of Mn in Zn2-xMnxSiO4 revealed that about 10% of initial Mn content were doped in Zn2SiO4 lattice. The photoluminescence of the synthesized phosphor showed maximum brightness at x=0.02, which is lower concentration than reported elsewhere. This was due to the increase in residual SiO2 at higher x value.