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A series of single-composition emission-tunable Ca9Y(PO4)7:Eu2+,Mn2+phosphors were synthesized by solid-state reaction. The energy transfer from Eu2+to Mn2+in Ca9Y(PO4)7host matrix was studied and demonstrated to be a resonant type via a dipole−quadrupole mechanism with the critical distance of ∼ 11 Å. The wavelength-tunable white light can be realized by coupling the emission bands centered at 486 and 638 nm ascribed to the contribution from Eu2+and Mn2+, respectively. By properly tuning the relative composition of Eu2+/Mn2+, chromaticity coordinates of (0.31, 0.33) can be achieved under excitation at 250−440 nm. Moreover, white-light-emitting diodes were fabricated through the integration of 365 nm chips and single composition white-light-emitting phosphors (Ca0.975Eu0.01Mn0.015)9Y(PO4)7into a single package shows a cool white light of 7200 K, color rendering index of 76, and color coordinates of (0.30, 0.31) close to that of ideal white light can be achieved.

The nanometer-sized zinc sulfide (ZnS) as a blue-emitting phosphor was prepared in a water-in-supercritical CO2microemulsion. The nanoparticles were characterized by XRD, TEM, and PL. XRD analysis shows that the average crystalline size of ZnS nanometer-scale samples is about 2–3 nm. Emission intensity of the ZnS nanophosphors obtained by the process is higher than that micrometer-sized ZnS.

Novel green-emitting phosphors of Ca3Y2(Si3O9)2:Ce3+,Tb3+ was successfully synthesized by solid-state reaction. Not merely the luminescence properties and energy transfer of Ca3Y2(Si3O9)2:Ce3+,Tb3+, the calculation of the energy transfer critical distance between Ce3+ and Tb3+ ions are also investigated in this work. By codoping Ce3+ into Ca3Y2(Si3O9)2:Tb3+, the emission intensity is dramatically enhanced by 5.8 times and the emission intensity is 126% as compared to that of ZnS:Cu,Al. We has been demonstrated that the energy transfer from Ce3+ to Tb3+ is a resonant type via dipole-dipole mechanism with the energy transfer critical distance of 6.78 Aå. The preliminary data demonstrate that the novel phosphor can emit blue to yellow-greenish under UV excitation and it exhibit the potential to act as UV convertible phosphor.

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Green-emitting phosphors of Ca3Y2(Si3O9)2:Ce3+,Tb3+have been synthesized by solid-state reaction. The luminescence properties were characterized by photoluminescence (PL) and photoluminescence excitation spectra, reflection spectra, and a detection system using an integrating sphere equipped with a spectrofluorometer. With Ce3+co-doping as a sensitizer, the PL intensity of Ca3Y2(Si3O9)2:Ce3+,Tb3+was found to increase dramatically by a factor of 5.8. For comparison, the emission intensity of composition-optimized Ca3Y2(Si3O9)2:Ce3+,Tb3+is 126% of green commodity, ZnS:Cu,Al. The quantum efficiency of Ca3Y2(Si3O9)2:Ce3+,Tb3+is as high as 77% compared to ZnS:Cu,Al (53%). The energy transfer from Ce3+to Tb3+is also of resonant type via a dipole–dipole mechanism with the energy-transfer critical distance of 6.78 Å. By utilizing the principle of energy transfer and appropriate tuning of activator contents, we are currently evaluating the potential application of Ca3Y2(Si3O9)2:Ce3+,Tb3+as a highly efficient UV-convertible phosphor.

A series of Ca10K(PO4)7:Eu2+,Mn2+(CKP:Eu2+,Mn2+)phosphors was synthesized by solid-state reaction. Under an optimal excitation of 347 nm, we have observed a blue emission band at 467 nm and a red emission band at 634 nm, which resulted from Eu2+and Mn2+, respectively. The energy transfer from Eu2+to Mn2+in CKP host matrix is of a resonant type via a dipole–quadrupole mechanism. By properly varying the ratio of Eu/Mn, the emission hue can be tuned from blue (0.18,0.21), to white (0.30,0.24), and finally to red (0.35,0.24). The intensity of composition-optimized CKP:Eu2+is about 30% of BaMgA110O17:Eu2+. The measurement of thermal quenching for CKP:Eu2+,Mn2+and yttrium aluminum garnet:Ce3+was also compared and investigated in the study. The (CKP:Eu2+,Mn2+)phosphor may serve as a candidate for UV light-emitting diode application.

A series of new phosphors of CaAlBO4:RE3+(RE=Ce,Tb,Eu)were synthesized by conventional solid-state reactions. The X-ray diffraction data indicate that a pure phase of CaAlBO4:RE3+can be successfully obtained. The photoluminescence (PL) spectra, quantum efficiency, and CIE coordinates of CaAlBO4:RE3+were investigated. The PL and PL excitation spectra indicate that the emission wavelengths of CaAlBO4:Ce3+are 372 and 398 nm (with full width at half maximum of 33 nm) attributed to the 4f65d–4f7transition of the Ce3+activator, respectively. CaAlBO4:Tb3+displays green emission at 483, 543, 584, and 620 nm, while CaAlBO4:Eu3+shows a dominating emission peak at 621 nm, which is attributed to the Eu3+D50−F72transition. The quantum efficiencies of optimized CaAlBO4:Ce3+, CaAlBO4:Tb3+, and CaAlBO4:Eu3+were found to be 43, 21, and 19%, respectively. The phosphors may provide a new kind of luminescent material under UV excitation.