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High-color-rendering illumination is an important application direction in the development of white-light-emitting diodes (WLEDs). In this work, the Ce3+-activated Sr3Sc4O9-CaSc2O4 phosphors are successfully obtained by cation exchange from Sr3Sc4O9:Ce3+. Due to the high reaction activity and reaction rate in CaCl2 melt, the exchange process can be realized under much lower temperature than that of traditional high-temperature sintering, even near the melting point of CaCl2 (1058 K). The color tunability of as-prepared phosphors from orange to green is also easily tailored by adjusting the content of CaCl2. What is more, combining the exchanged phosphor and a blue LED, a high-color-rendering warm WLED is also demonstrated (CCT = 3555 K, Ra = 88, R9 = 94), which is comparable to most of commercial WLEDs. The obtained results not only manifest the potential application of ion exchange in preparing luminescent materials and adjusting corresponding spectral properties, but also provide a promising platform in developing the high-color-rendering warm white-light illumination.

Eu3+-doped SrGa2O4 from γ- to β-phases is successfully manipulated by controlling sintered temperature from 1273 K to 1673 K. The related structural changes are characterized by the thermal analysis, Rietveld refinement and Raman investigation. And on that basis, the photoluminescence (PL) survey is used to study the corresponding crystal-field splittings of Eu3+ ions in γ- and β-SrGa2O4, which shows the obvious difference in the 4f-4f energy transitions of Eu3+ ions between two SrGa2O4 phases, especially in the non-degenerate 5D0→7F0 transition region. Both γ- and β-SrGa2O4 show two 5D0→7F0 transition peaks, being in agreement with the two nonequivalent Sr sites in each SrGa2O4 phase. For γ-SrGa2O4, it is 580.8 nm (SrO7) and 579 nm (SrO8), respectively, and for β-SrGa2O4, it is 579.6 nm (SrO7) and 578.7 nm (SrO8), respectively. The difference of Eu3+ crystal field splitting between SrO7 sites and SrO8 sites in γ-SrGa2O4 is larger than that in β-SrGa2O4, which is mainly derived from the larger polyhedral difference between two Sr sites (SrO7 and SrO8). What discussed in this work manifests the sensitive response of Eu3+ ions for the change of local structural surroundings, and further indicates the potential application of rare-earth fluorescent probes in the field of phase identification.

The design and development of phosphors have received widespread attention with the increasing demand for white light-emitting diodes (WLEDs). In this work, a series of Ce3+-doped gadolinium scandium aluminum garnet (GSAG) phosphors were successfully synthesized by the sol-gel method, and the relevant structural, optical, and lighting properties were investigated in detail. The optimal sintering process was optimized to 1873 K for 5 h under an Ar/H2 reduction atmosphere, and the structural analysis showed that the lattice parameters were gradually increased with an increase in Sc/Al substitution. The cationic substitution of GSAG adjusted the local coordination environments of Ce3+ ions effectively, and the increasing Sc3+-doped concentrations gave rise to a blue-shift of photoluminescence spectra and a decline of related fluorescence lifetimes. Furthermore, the doping concentration of Ce3+ ions was optimized and the concentration quenching mechanism was also clarified. Based on the temperature-dependent spectral survey, the thermally induced fluorescence quenching behavior of GSAG:Ce3+ (x = 1 at.%, y = 0.65) was measured, and the relevant activation energy was evaluated to 0.28 eV. Moreover, the effects of different Sc/Al substitution ratios on the thermal stability of GSAG:Ce3+ samples were also tested. Benefited from the tunable emission of GSAG:Ce3+ phosphors, the WLEDs device was fabricated by combining with a blue LED, yielding the Ra value of 82.1 and the CCT value of 3981 K. This study indicates the potential application of GSAG:Ce3+ phosphors in white lighting and also provides some guiding inspirations in the exploration of new garnet phosphors.

In this work, the electronic structure modulation of ScOOH is proposed, and the density functional theory (DFT) calculations indicate the introduction of oxygen vacancies (VO) in ScOOH could generate the defect-related energy levels within the band gap. The following photoluminescence and chemical state analyses verify the existence of VO in the two ScOOH phases, and the temperature-dependent fluorescence investigation further confirms the thermal sensitivity of VO-related emissions. On that basis, a self-calibration temperature sensing strategy is demonstrated with a combination of the emissions of VO defects and lanthanide luminescent probes (Eu3+ and Tb3+), yielding a relative sensitivity of 1.33%·K-1 (173 K). The findings in this work lay a foundation for developing LnOOH materials by the electronic structure modulation and further broaden the relevant optoelectronic applications.