Effect of heat treatments on the luminescence properties of Zn2SiO4:Mn2+ phosphors prepared by glycothermal methods

Manganese-doped Zn₂SiO₄ phosphors with different crystal structures and morphologies were synthesized by glycothermal reactions of zinc acetate dihydrate and manganese(II) acetate tetrahydrate with tetraethyl orthosilicate in various glycols at 315 °C. The reactions in 1,3-propanediol and 1,4-butanediol yielded α-Zn₂SiO₄:Mn²⁺, whereas the reactions in ethylene glycol and 1,5-pentanediol yielded β-Zn₂SiO₄:Mn²⁺ and ZnO, respectively. The samples obtained in 1,4-butanediol and 1,3-propanediol emitted green light (522 nm), and the sample prepared in 1,4-butanediol showed a higher emission intensity. The photoluminescence intensity of the Zn_1.96Mn_0.04SiO₄ phosphor prepared by a glycothermal reaction in 1,4-butanediol and subsequently calcined at 1100 °C was twice as high as that of the sample synthesized by a conventional solid-state reaction. The high emission efficiency was obtained because the highly homogeneous distribution of Mn²⁺ in the α-Zn₂SiO₄ host synthesized by the glycothermal reaction was maintained during calcination treatment in air.