A novel dual-emitting temperature sensor, Sr1.7Zn0.3CeO4F0.2:Eu3+, is successfully synthesized via a ceramic reaction. Powder X-ray diffraction patterns and Rietveld refinement verify the phase purity of the sensor. Its photoluminescence spectrum exhibits a pronounced intrinsic dual emission, theoretically divided by the wavelength of 570 nm: one stems from Eu3+ and the other is derived from the Ce4+–O2− charge transfer state. The temperature-dependent luminescence spectra of the dual-emission thermophosphor demonstrate its superior sensitivity towards ambient temperature. Further studies illustrate that the intensity ratio between the aforementioned two parts, as a function of temperature, is perfectly linear over a broad temperature window, yielding a convenient and accurate approach to obtain the temperature of a target, measured using the noncontact self-referencing model. We also investigate the basis of the underlying mechanism of Sr1.7Zn0.3CeO4F0.2:Eu3+ as a dual-emission thermometric sensor. The research herein shows that the intrinsic dual-emission sensor, as a new-fashioned thermophosphor, displays potential for ratiometric intensity measurements in thermometry domains.

Although a variety of Bi3+-activated common luminescent materials have been investigated, few Bi3+-doped long afterglow phosphors have been discovered up to now. In this work, we developed a novel long afterglow material KGaGeO4:Bi3+ by solid-state reaction. The highlight of this work is the observation of bright cyan to blue color tunable long afterglow of KGaGeO4:Bi3+. The structural information of the samples was studied in detail using Rietveld refinement. Photoluminescence and phosphorescence properties of the phosphor were investigated systematically. The reason why the photoluminescence and phosphorescence color can be tuned has been discussed. A bright long afterglow could be observed by the naked eye for 3 hours in the dark after ultraviolet irradiation was ceased. Moreover, we have analyzed the reason why the KGaGeO4 host is suitable for Bi3+ to generate afterglow emission by exploring the nature of traps in KGaGeO4:Bi3+ with the help of thermoluminescence spectra. In this phosphor, Bi3+ ions doped in K+ sites behave as luminescence centers, while negatively charged defects serve as hole-trapping centers. In view of the experimental results, a feasible afterglow mechanism of KGaGeO4:Bi3+ was also proposed and discussed.

•A series of SC:0.01Eu3+ materials with different charge compensators were synthesized and further investigated by EDS, XPS, XRD and Rietveld refinements to verify the purity.•The effects of charge compensators on optical features were systematically studied via the reflectance and photoluminescence spectra.•The anionic charge compensators, especially F−, greatly enhanced photoluminescence properties, which may provide a novel method to synthesize and improve phosphors.Presently enormous interest in the modification of photoluminescence properties of Sr2CeO4:Eu3+ with charge compensators has been stimulated. Here we report the effect of charge compensators on optical characteristic of Sr2CeO4:Eu3+ synthesized by altering types of charge compensators and propose the possible explanation. The conclusion is made that anionic charge compensators, especially F−, may provide a novel approach to the development and improvement of the phosphors.

A series of novel red-emitting Sr1.7Zn0.3CeO4:Eu3+ phosphors were synthesized through conventional solid-state reactions. The powder X-ray diffraction patterns and Rietveld refinement verified the similar phase of Sr1.7Zn0.3CeO4:Eu3+ to that of Sr2CeO4. The photoluminescence spectrum exhibits that peak located at 614 nm (5D0–7F2) dominates the emission of Sr1.7Zn0.3CeO4:Eu3+ phosphors. Because there are two regions in the excitation spectrum originating from the overlap of the Ce4+–O2– and Eu3+–O2– charge-transfer state band from 200 to 440 nm, and from the intra-4f transitions at 395 and 467 nm, the Sr1.7Zn0.3CeO4:Eu3+ phosphors can be well excited by the near-UV light. The investigation of the concentration quenching behavior, luminescence decay curves, and lifetime implies that the dominant mechanism type leading to concentration quenching is the energy transfer among the nearest neighbor or next nearest neighbor activators. The discussion about the dependence of photoluminescence spectra on temperature shows the better thermal quenching properties of Sr1.7Zn0.3CeO4:0.3Eu3+ than that of Sr2CeO4:Eu3+. The experimental data indicates that Sr1.7Zn0.3CeO4:Eu3+ phosphors have the potential as red phosphors for white light-emitting diodes.Keywords: concentration quenching; photoluminescence; red-emitting phosphors; thermal quenching;

•Bluish green long-lasting phosphorescence Ca9Bi(PO4)7:Eu2+,Dy3+ phosphor was synthesized for the first time.•The luminescence and phosphorescence properties of Ca9Bi(PO4)7:Eu2+,Dy3+ were systematically studied.•The corresponding afterglow mechanism of this phosphor was discussed.A new long-lasting phosphorescence phosphor Ca9Bi(PO4)7:Eu2+,Dy3+ was synthesized by solid state reaction and its long-lasting phosphorescence properties were investigated for the first time. The X-ray powder diffraction, photoluminescence, long-lasting phosphorescence spectra, decay curves and thermoluminescence curves were measured. The Ca9Bi(PO4)7:Eu2+,Dy3+ phosphor exhibits an asymmetric emission centered at 475 nm, which can be ascribed to the 4f65d1–4f7 electronic transition of Eu2+. For the optimized sample, the bright bluish green long-lasting phosphorescence could be observed for 5 h by naked eyes after the excitation source was removed. The long-lasting phosphorescence spectra show that the co-doping of Dy3+ ions greatly enhance the intensity of the long-lasting phosphorescence. Meanwhile, the long-lasting phosphorescence mechanism of this phosphor was discussed. Based on our study, Dy3+ ions are suggested to increase the density of electron or hole traps so as to improve the performance of the bluish green phosphorescence of Eu2+, including the intensity and persistent time.

•Green long-lasting phosphorescence phosphor Ca14Mg2(SiO4)8:Eu2+, Dy3+ was prepared.•The luminescence and phosphorescence properties were investigated systematically.•Long-lasting phosphorescence mechanism of this phosphor was generally discussed.A novel silicate long-lasting phosphorescence phosphor Ca14Mg2(SiO4)8:Eu2+, Dy3+ was prepared by high-temperature solid state reaction. Its properties were investigated systematically by powder X-ray diffraction patterns, Rietveld refinements, photoluminescence spectra, long-lasting phosphorescence spectra, phosphorescence decay curves, and thermoluminescence spectra. Under the excitation of 400 nm, Ca14Mg2(SiO4)8:Eu2+, Dy3+ phosphor exhibits green light with the peak at 505 nm, which is attributed to the 4f65d1–4f7 electronic transition of Eu2+ ions. It is also found that Ca14Mg2(SiO4)8:Eu2+, Dy3+ phosphor can emit green persistent phosphorescence after the irradiation of ultraviolet or visible light is stopped. And for the optimal sample, the green persistent luminescence can last for about half an hour. The co-doping of Dy3+ ions greatly enhances the intensity and duration of the persistent luminescence in Ca14Mg2(SiO4)8:Eu2+, Dy3+ phosphor. However, the peak position of the long-lasting phosphorescence spectrum is red shift compared to that of the photoluminescence spectrum, and the possible reason was analyzed. Meanwhile, the long-lasting phosphorescence mechanism of this phosphor was also discussed.

•The synthesized Sr2CeO4:Eu3+ phosphors were firstly probed by the Rietveld refinement.•The luminescence properties of Sr2CeO4:Eu3+ were systematically investigated.•The energy transfer from the Ce4+–O2− CTS to Eu3+ was discussed in detail based on the Inokuti–Hirayama theory.A series of color-tunable Sr2CeO4:Eu3+ phosphors have been successfully synthesized. The Rietveld refinement was firstly used to probe the phase purity and the structure of Sr2CeO4:Eu3+. The photoluminescence excitation spectra exhibit that the phosphors show a broad excitation band from 200 to 400 nm, which concurs well with the commercial near-UV LED. The photoluminescence spectra vary with the dopant content due to the energy transfer and the tunable blue-red color can be simply achieved by altering the doped Eu3+ ions concentrations. On the basis of the Inokuti–Hirayama theory, we obtained that the dipole-dipole interaction type takes charge for the energy transfer from the Ce4+–O2− charge-transfer state transition to Eu3+ ions and the schematic was plotted to illuminate the possible energy transfer process. The experimental results indicate that Sr2CeO4:Eu3+ phosphors may be potentially used as promising single-phased phosphors for near-UV white light-emitting diodes applications.

Although a variety of Bi3+-activated common luminescent materials have been investigated, few Bi3+-doped long afterglow phosphors have been discovered up to now. In this work, we developed a novel long afterglow material KGaGeO4:Bi3+ by solid-state reaction. The highlight of this work is the observation of bright cyan to blue color tunable long afterglow of KGaGeO4:Bi3+. The structural information of the samples was studied in detail using Rietveld refinement. Photoluminescence and phosphorescence properties of the phosphor were investigated systematically. The reason why the photoluminescence and phosphorescence color can be tuned has been discussed. A bright long afterglow could be observed by the naked eye for 3 hours in the dark after ultraviolet irradiation was ceased. Moreover, we have analyzed the reason why the KGaGeO4 host is suitable for Bi3+ to generate afterglow emission by exploring the nature of traps in KGaGeO4:Bi3+ with the help of thermoluminescence spectra. In this phosphor, Bi3+ ions doped in K+ sites behave as luminescence centers, while negatively charged defects serve as hole-trapping centers. In view of the experimental results, a feasible afterglow mechanism of KGaGeO4:Bi3+ was also proposed and discussed.