Site-selective luminescence in Ca-doped Sr₂YNbO₆:Eu³⁺ phosphors for high-color-purity red emission

Narrow-band red phosphors excited by blue light are vital for high-color-rendering lighting and wide-color-gamut displays. Nevertheless, the commonly utilized red phosphors exhibit considerable deficiencies in hydrothermal stability and color purity, thus constraining their practical usage. In this study, by using a developed doping strategy with Ca²⁺ to regulate a local crystal field and the possible preferential occupation behavior of the Sr₂YNbO₆:Eu³⁺ red phosphor with a double perovskite structure, it is found that their luminescence intensity and thermal stability are significantly enhanced. High-resolution scanning transmission electron microscope (STEM) measurements equipped with an aberration corrector revealed that Eu³⁺ occupied the Sr²⁺ or Y³⁺ sites, forming two emission centers. This resulted in significant changes in the emission intensity at 594 nm and 611 nm with changes in the excitation wavelength. Furthermore, the introduction of Ca²⁺ can increase the proportion of Eu³⁺ at the Sr²⁺ site, thereby enhancing the emission of the ⁵D₀ → ⁷F₂ transition at 611 nm. Meanwhile, we have significantly improved the color purity and thermal stability of the obtained red phosphors. The current findings reveal the site-selective luminescence mechanism in Eu³⁺-activated double perovskite structures and propose a cation substitution strategy to optimize excitation and emission simultaneously. This approach may provide an effective pathway for the design of high-performance red phosphors for advanced optoelectronic applications.