Thermal analysis and mechanism of formation of Zn2SiO4:Mn phosphor under heating of synthetic hemimorphite

Abstract Detailed study of thermal decomposition of synthetic hemimorphite was performed to understand the process formation of metastable and stable structural modifications of Zn2SiO4:Mn phosphor. X-ray powder diffraction, differential-thermal and thermogravimetric methods are demonstrated that dehydration product of Zn4[Si2O7](OH)2•H2O at 680 °C is mixture of metastable β-Zn2SiO4 and α-Zn2SiO4. At further heating, metastable phase undergoes transition to α-Zn2SiO4 at 873 °C. Luminescence spectrum of Zn2SiO4:Mn in phase coexistence region is wide band with two maxima, which explains the loss of purity of green glow of phosphor. Luminescence spectrum of sample annealed at the higher temperature is represented by single maximum, corresponding to green emission of α-Zn2SiO4:Mn. Identification of thermal effects indicates that at 1500 °C α-Zn2SiO4 turns into stable β-Zn2SiO4 and exists up to melting point 1512 °C. Information on phase transition of stable modifications α-Zn2SiO4→β-Zn2SiO4 complements phase equilibrium diagram of system SiO2–ZnO.