Enhanced Photoluminescence and Thermal Properties of Size Mismatch in Sr_{2.97–<i>x</i>–<i>y</i>}Eu_0.03Mg_<i>x</i>Ba_<i>y</i>SiO₅ for High-Power White Light-Emitting Diodes

In this Study, Mg²⁺ and Ba²⁺ act to enhance the maximum emission of Sr_2.97SiO₅:0.03Eu²⁺ significantly and redshift the emission band to the orange-red region in Sr_{2.97–<i>x</i>–<i>y</i>}Mg_<i>x</i>Ba_<i>y</i>SiO₅:0.03Eu²⁺. Size mismatch between the host and the doped cations tunes the photoluminescence spectra shift systematically. A slight blue shift when increasing the amount of Mg²⁺ occurs in the Sr_{2.97–<i>x</i>}Eu_0.03Mg_<i>x</i>SiO₅ lattices, and a rapid red shift occurs when Ba²⁺ is codoped in the Sr_{2.57–<i>y</i>}Eu_0.03Mg_0.4Ba_<i>y</i>SiO₅ lattices. The emission spectra were tuned from 585 to 601 nm by changing the concentration of Ba²⁺. Accordingly, we propose the underlying mechanisms of the changes in the photoluminescence properties by adjusting the cation composition of phosphors. The influence of the size mismatch on the thermal quenching is also observed. This mechanism could be widely applied to oxide materials and could be useful in tuning the photoluminescence properties, which are sensitive to local coordination environment. The emission bands of Sr_{2.97–<i>x</i>–<i>y</i>}Eu_0.03Mg_<i>x</i>Ba_<i>y</i>SiO₅ show the blue shift with increasing temperature, which could be described in terms of back tunneling of the excited electrons from the low-energy excited state to the high-energy excited state. Thus, the Sr_{2.97–<i>x</i>–<i>y</i>}Eu_0.03Mg_<i>x</i>Ba_<i>y</i>SiO₅ phosphors could have potential applications in the daylight LEDs or warm white LEDs