Multiple site occupancy induced yellow-orange emission in an Eu2+-doped KSr6Sc(SiO4)4 phosphor towards optical temperature sensors

Abstract

Phosphors have attracted significant interest as potential optical temperature sensors in recent years. In our work, a new blue-light stimulated KSr₆Sc(SiO₄)₄:Eu²⁺ phosphor with decorative kröhnkite-like octahedral tetrahedral chains was successfully synthesized. Multiple site occupancy occurred in KSr₆Sc(SiO₄)₄:Eu²⁺ and induced a yellow-orange emission band with a peak at 571 nm and an FWHM of 91 nm. Gaussian fitting and time-resolved photoluminescence mapping were combined to analyze the occupation of Eu²⁺ in five Sr²⁺ sites. In the meantime, the site occupation preference, energy transfer process, and thermal quenching mechanism of Eu²⁺ emission centers have been comprehensively examined. Under 450 nm excitation, the optimal sample possesses an acceptable quantum efficiency (EQE = 17.3%) and a high sensitivity between luminescence properties and temperature variation ranging from 200 to 475 K. The optimal sample's relative sensor sensitivity achieves a maximum value of 3.53% K⁻¹ at 475 K. The phosphor KSr₆Sc(SiO₄)₄:0.07Eu²⁺ presents the potentiality as an optical thermometer.