Blue-excitable orange-red-emitting M₃Y(PO₄)₃:Pr³⁺ (M = Ba, Sr, Ca) phosphors for multifunctional applications

Abstract

Research on multifunctional luminescent materials has become an emerging trend for new applications of optical sensing, monitoring, anticounterfeiting, lighting, etc. Herein, a library of Pr3+-doped M3Y(PO4)3 (M = Ba, Sr, Ca) phosphors was prepared for careful spectroscopic studies in potential lighting and optical temperature sensing applications. With the help of density functional theory calculation, diffuse reflectance spectra, and steady/dynamic photoluminescence spectra, the effects of alkaline earth metals on the fluorescence properties of M3Y(PO4)3:Pr3+ were studied systematically. Under the excitation of blue ∼ 445 nm, orangish-red fluorescence of approximately 602 nm was efficiently detected due to Pr3+ 1D2 → 3H4 transition, which becomes stronger by regulating alkaline-earth elements from Ba to Sr and to Ca. An optimized Ca3Y(PO4)3:0.7%Pr3+ sample was validated with excellent thermal stability 89%@423 K and further applied to fabricate a white light emitting diode by combining with commercial YAG:Ce3+ phosphors on a 445 nm blue chip. Specifically, CIE chromaticity coordinates (0.3510, 0.3650) and correlated color temperature (∼ 4838 K) were obtained for an obvious improvement. Moreover, optical thermometry properties of Ca3Y(PO4)3:0.7%Pr3+ were explored on basis of Pr3+ 3P0-3P1 thermally coupled energy levels. Their fluorescence intensity ratios following the Boltzmann equation could be operated over 298-598 K with superior relative sensitivity ∼ 0.87% K-1 at 298 K. These interesting results for multifunctional luminescence will greatly promote the development of novel Pr3+-doped luminescent materials as well as the related photoelectric devices.