Improvement of Luminescence Properties of Eulytite Single-Phase White Emitting Ca3Bi (PO4)3: Ce3+/Dy3+ Phosphor

To reduce the issue of tri-primary color reabsorption, a new approach for single-phase phosphors as light-emitting diodes (LEDs) has been recommended. The structures, morphology, photoluminescence, thermal stability, and luminescence mechanism of a variety of Ca₃Bi (PO₄)₃ (CBPO): Ce³⁺/Dy³⁺ phosphors were investigated. XRD characterization showed that all CBPO samples were eulytite structures. Furthermore, the energy transfer process from Ce³⁺ to Dy³⁺ in CBPO is systematically investigated in this work, and the color of light can be adjusted by changing the ratio of doped ions. Under UV light, energy is transferred from Ce³⁺-Dy³⁺ mainly through quadrupole-quadrupole interactions in the CBPO host, and doping with different Dy³⁺ concentrations tunes the emission color from blue to white. The thermal stability of the CBPO: 0.04Ce³⁺, 0.08Dy³⁺ samples is outstanding, and the CIE coordinates of the samples after emission have little effect with temperature, while their emission intensity at 423 K is as strong as that at room temperature, reaching 90%. The above results indicate that this CBPO material has great potential as a white light phosphor under near-UV excitation at the optimized concentration of Ce³⁺ and Dy³⁺.

Simultaneous Thermal Enhancement of Upconversion and Downshifting Luminescence by Negative Thermal Expansion in Nonhygroscopic ZrSc(WO4)2PO4:Yb/Er Phosphors

Thermal quenching (TQ) is still a critical challenge for lanthanide (Ln³⁺)-doped luminescent materials. Herein, we report the novel negative thermal expansion nonhygroscopic phosphor ZrSc(WO₄)₂PO₄:Yb³⁺/Er³⁺. Upon excitation with a 980 nm laser, a simultaneous thermal enhancement is realized on upconversion (UC) and downshifting (DS) emissions from room temperature to 573 K. In situ temperature-dependent X-ray diffraction and photoluminescence dynamics are used to reveal the luminescence mechanism in detail. The coexistence of the high energy transfer efficiency and the promoted radiative transition probability can be responsible for the thermally enhanced luminescence. On the basis of the luminescence intensity ratio of thermally coupled energy levels ²H_11/2 and ⁴S_3/2 at different temperatures, the relative and absolute sensitivities of the targeted samples reach 1.10% K^-1 and 1.21% K^-1, respectively, and the low-temperature uncertainty is approximately 0.1-0.4 K on the whole temperature with a high repeatability (98%). Our findings highlight a general approach for designing a hygro-stable, thermostable, and highly efficient Ln³⁺-doped phosphor with UC and DS luminescence.