Effect of sintering temperature on the emission-spectrum-shape-evolution of Sr₂SiO₄:Eu²⁺ phosphor

Color rendering index and color temperature are the key factors for the LEDs application. The two points are closely related to the emission spectrum shape of phosphors. As the key factors for the LEDs application, both the above aspects are closely dependent on the emission spectrum shape of phosphors. In this study, the emission spectrum shape has been adjusted via a home designed route. A combination of structural, morphological, and optical characterization techniques has been used to study the shape evolution mechanism. The structural results show that the Sr₂SiO₄ phase has not been changed with the sintering temperature increasing, but the emission spectrum shape has changed dramatically, meanwhile, the colorimetric coordinate moves from blue-green to green region. Gaussian fitting method has been used to treat the emission spectrum, and the as-obtained results indicate the emission spectrum contains two single bands, which come from the 4f⁷(⁷S_7/2)–4f⁶(⁷F_J)5d¹ transition of Eu²⁺ on the different Sr sites in the Sr₂SiO₄ crystal. The intensity of the two single bands is driven by sintering temperature, because of the difference between the energy barrier of the Eu²⁺ occupying the different Sr sites in the matrix crystal. Moreover, the mechanism of the above phenomenon has also been studied by means of first principles method, and the obtained results agree well with the former deduction.