Energy-Transfer-Engineered CaO:Eu ^2+/3+ , Tb ³⁺ , Cl ^– Phosphor Enabling Enhanced Multicolor Luminescence, White-Light Emission and Optical Thermometry

With their tunable multicolor light emission and ability to sense temperature optically, single-host multifunctional materials offer great practical promise and are thus the subject of extensive study. This study adopted a two-step approach─first a carbonation method, then a double-crucible carbon reduction process─to prepare CaO:Eu^2+/3+,Tb³⁺,Cl^- phosphor, which crystallizes in a face-centered cubic structure with the space group <i>Fm-</i>3<i>m</i>. Under ultraviolet excitation, the phosphors simultaneously emit blue light (Eu²⁺), green light (Tb³⁺), and red light (Eu³⁺). Notably, the introduction of Tb³⁺ ions, which serve as an energy bridge, not only contributes the green emission but also enhances the intensity of red light associated with the Eu³⁺ ions. Therefore, tuning the Tb³⁺ doping concentration allows the CaO:Eu^2+/3+,Tb³⁺,Cl^- phosphor to produce white light. Additionally, tunable luminescence is achievable through adjusting either the excitation wavelength or the Tb³⁺ concentration, and this characteristic greatly improves the material's applicability. As a consequence, the as-fabricated CaO:0.01 Eu^2+/3+,0.008 Tb³⁺,0.06 Cl^- phosphor is a promising candidate for white light-emitting diodes (WLEDs), display technologies, and optical anti-counterfeiting applications. Moreover, the material exhibits non-contact temperature sensing capability, facilitated by the fluorescence intensity ratio (FIR) method. Based on the calculated absolute (S_a) and relative sensitivities (S_r), the CaO:Eu^2+/3+,Tb³⁺,Cl^- phosphor also exhibits potential application value in optical thermometry.