Tunable luminescent Eu²⁺-doped dicalcium silicate polymorphs regulated by crystal engineering

In this work, tunable luminescence of dicalcium silicate doped with Eu²⁺ ions is demonstrated based on crystal engineering. Five types of dicalcium silicate polymorphs (γ-, β-, α_L′-, α_H′-, α-Ca₂SiO₄) are synthesized by incorporating a crystal-phase stabilizer (CPS), in order to afford variable accommodation frameworks for the Eu²⁺ activator. Tunable luminescence is observed as the polymorph transforms from one crystal form into another. In addition, the luminescence of Eu²⁺ in peculiar crystal-phase Ca₂SiO₄ hosts is further customized by crystal-site engineering, which regulates the coordination environment of Eu²⁺ in multiple types of Ca²⁺ sites. The luminescence properties of our Eu²⁺-doped dicalcium silicate polymorphs show promising prospects for LED lighting applications.