Luminescence behavior of europium activated strontium aluminate phosphors by solid state reaction method

Abstract

The SrAl₂O₄:Eu²⁺ and SrAl₂O₄:Eu³⁺ phosphors were prepared by the traditional high temperature solid state reaction method. The crystal structures of the prepared phosphors were consistent with standard monoclinic phase with a space group P2₁. The different TL kinetics parameters [activation energy (E), frequency factor (s) and order of the kinetics (b)] were evaluated and compared by using the peak shape method. Under the ultra-violet excitation (344 nm), the SrAl₂O₄:Eu²⁺ phosphor would emit green light, belonging to the broad emission band ascribed to the 4f⁶5d¹ → 4f⁷ transition. The emission spectrum of SrAl₂O₄:Eu³⁺ phosphor was consisted of two emission peaks at 590 and 615 nm, which were attributed to ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ of Eu³⁺ ions. The strongest excitation band at 396 nm can be assigned to ⁷F₀ → ⁵L₆ transition of Eu³⁺ ions due to the typical f–f transitions of 4f⁶ configuration. Commission International de I’Eclairage color coordinates of prepared SrAl₂O₄:Eu²⁺ and SrAl₂O₄:Eu³⁺ phosphors were suitable as green and orange-red light respectively. The mechanoluminescence (ML) intensity of prepared SrAl₂O₄:Eu²⁺ and SrAl₂O₄:Eu³⁺ phosphors increase linearly with increasing impact velocity of the moving piston (load). Thus the present investigation indicates that the piezoelectricity was responsible to produce ML in sintered phosphors. Decay rates for different impact velocities were also calculated using curve-fitting techniques. The time of the peak ML and the rate of decay did not change significantly with respect to increasing impact velocity of the moving piston and peak ML intensity varied linearly.