Studies on the luminescence properties of europium doped strontium alumino-silicate phosphors by solid state reaction method

The Sr₂Al₂SiO₇:Eu²⁺ and Sr₂Al₂SiO₇:Eu³⁺ phosphors were prepared by the traditional high temperature solid state reaction method. The crystal structures of sintered phosphors were gehlenite type structure which belongs to the tetragonal crystallography with space group \( {\rm P}\bar{42}_{1}{\rm m} \). Thermoluminescence properties of these phosphors were investigated and results were also compared. Under the ultra-violet excitation (345 nm), the Sr₂Al₂SiO₇:Eu²⁺ phosphor would emit bluish-green (cyan) light, belonging to the broad emission band ascribed to the 4f ⁶5d ¹ → 4f ⁷ transition. The emission spectrum (λ_ex = 395 nm) of Sr₂Al₂SiO₇:Eu³⁺ phosphor were consisted of two emission peaks at 593 and 613 nm, which were attributed to ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ of Eu³⁺ ions. The strongest excited band at 395 nm can be assigned to ⁷F₀ → ⁵L₆ transition of Eu³⁺ ions due to the typical f–f transitions within Eu³⁺ of 4f ⁶ configuration. Commission International de I’Eclairage color coordinates of Sr₂Al₂SiO₇:Eu²⁺ and Sr₂Al₂SiO₇:Eu³⁺ phosphors were suitable as bluish-green and orange-red light emitting phosphors respectively. The mechanoluminescence (ML) intensity of Sr₂Al₂SiO₇:Eu²⁺ and Sr₂Al₂SiO₇:Eu³⁺ phosphors increase linearly with increasing impact velocity of the moving piston. Thus the present investigation indicates that the piezo-electrically induced de-trapping model is responsible to produce ML in sintered phosphors.