Search

Solid-state phosphor-converted white light-emitting diodes (pc-WLEDs) are the leading trend of the lighting industry in the 21st century. To pursue high quality WLED lighting, the development of highly efficient phosphors with tunable luminescence has become a hot research topic. Herein, we reported for the first time on Bi3+/Eu3+-doped Li3Ba2Y3(WO4)8 phosphors that exhibited tunable emission and high energy transfer efficiency of 89.90% from Bi3+ to Eu3+. The phase purity, microstructure, electronic structure and photoluminescence properties of these phosphors were studied in detail. Bi3+ and Eu3+ were effectively doped in Li3Ba2Y3(WO4)8 with an optical bandgap of 3.81 eV. The band structure and density of states were quantitatively evaluated by density functional theory simulation. At an excitation wavelength of 342 nm, the Bi3+-doped phosphor achieved yellow-green emission. By alloying Eu3+ into Li3Ba2Y3(WO4)8:Bi3+, the luminescence gradually turned red due to the energy transfer from Bi3+ to Eu3+. Moreover, the activation energy of the prepared phosphor was 0.1897 eV, demonstrating excellent thermal stability. Eventually, by combining Li3Ba2Y3(WO4)8:4%Bi3+,4%Eu3+ and a blue-emitting BAM:Eu2+ phosphor with a 365 nm ultraviolet chip, a WLED device with a high colour rendering index (Ra) of 78.7, chromaticity coordinates of (0.3401, 0.3131) and correlated colour temperature of 5080 K was successfully achieved. This work provided new insights into the design and development of color-tunable phosphors for white LEDs. [ABSTRACT FROM AUTHOR]

Research into red phosphors with a high color rendering index is particularly compelling, given the absence of a red component in the spectrum of commercial pc-WLEDs, which combine blue LED chips with yellow-emitting YAG:Ce3+ phosphors. Herein, we reported a novel Eu3+ activated Ca3Zn3Te2O12 red-emitting phosphor, synthesized using a conventional high-temperature solid-phase method. The phase and crystal structures were analyzed by powder X-ray diffraction and Rietveld refinement. The optimal excitation peak of the Ca3Zn3Te2O12:Eu3+ phosphor was located at 395 nm, matching those of conventional commercial near-ultraviolet chips. In addition, the Ca3Zn3Te2O12:9%Eu3+ phosphor exhibited good thermal stability, with an activation energy of 0.267 eV, and the CIE color coordinates hardly changed with temperature. Ultimatel, a high-quality white LED device was fabricated by combining Ca3Zn3Te2O12:9%Eu3+ red phosphor, a commercial BaMgAl10O17:Eu2+ blue phosphor, and(Ba,Sr)2SiO4:Eu2+ green phosphor with a 395 nm near-UV chip. Despite a substantial increase in the input current from 20 to 320 mA, the white-LED maintained a stable color rendering index of around 80, highlighting its consistent performance. These results indicated that Eu3+ activated Ca3Zn3Te2O12 phosphors are promising red emission candidates for white LEDs pumped by near ultraviolet chips. [ABSTRACT FROM AUTHOR]

A series of Ca3Y(GaO)3(BO3)4:Tb3+,Eu3+ phosphors were prepared by a high-temperature solid-state reaction. Their phase structures were confirmed by powder X-ray diffraction and the element distribution was measured using transmission electron microscopy elemental mapping. The photoluminescence emission and excitation spectra and fluorescence lifetime were studied and discussed in detail. The results revealed that Eu3+ ions can be efficiently sensitized by Tb3+ ions under near-UV excitation. In addition, the energy transfer efficiency can be controlled by adjusting the ratio of Eu3+ and Tb3+ to realize colour tunable emission from green to red. For Ca3Y(GaO)3(BO3)4:0.50Tb3+,0.10Eu3+, the emission intensity at 425 K is 78.11% of that at 300 K, being available to near-UV LEDs. [ABSTRACT FROM AUTHOR]

For drilling with oil-based mud, the oil slurry and film attached on wellbore or casing wall affect severely the cementing quality of the interface. To improve the compatibility between cement sheath and well surfaces, as well as increase the interface cementing quality, a preflush system BCS-020L was developed. The BCS-020L provides good compatibility with drilling mud and spacer fluid, and can effectively remove the oil-based drilling mud attached to the well and casing wall, with high cleaning efficiency, higher than 80%. Also, the BCS-020L could change cementing interface effectively from oil wet to water wet, and improve the cementing quality of interface efficiently. The preflush system BCS-010L has been successfully applied on Well LIUPING 1 in Yumen Oilfield with excellent cementing quality. [ABSTRACT FROM AUTHOR]

Solid-state phosphor-converted white light-emitting diodes (pc-WLEDs) are the leading trend of the lighting industry in the 21st century. To pursue high quality WLED lighting, the development of highly efficient phosphors with tunable luminescence has become a hot research topic. Herein, we reported for the first time on Bi 3+ /Eu 3+ -doped Li 3 Ba 2 Y 3 (WO 4 ) 8 phosphors that exhibited tunable emission and high energy transfer efficiency of 89.90% from Bi 3+ to Eu 3+ . The phase purity, microstructure, electronic structure and photoluminescence properties of these phosphors were studied in detail. Bi 3+ and Eu 3+ were effectively doped in Li 3 Ba 2 Y 3 (WO 4 ) 8 with an optical bandgap of 3.81 eV. The band structure and density of states were quantitatively evaluated by density functional theory simulation. At an excitation wavelength of 342 nm, the Bi 3+ -doped phosphor achieved yellow-green emission. By alloying Eu 3+ into Li 3 Ba 2 Y 3 (WO 4 ) 8 :Bi 3+ , the luminescence gradually turned red due to the energy transfer from Bi 3+ to Eu 3+ . Moreover, the activation energy of the prepared phosphor was 0.1897 eV, demonstrating excellent thermal stability. Eventually, by combining Li 3 Ba 2 Y 3 (WO 4 ) 8 :4%Bi 3+ ,4%Eu 3+ and a blue-emitting BAM:Eu 2+ phosphor with a 365 nm ultraviolet chip, a WLED device with a high colour rendering index ( R a ) of 78.7, chromaticity coordinates of (0.3401, 0.3131) and correlated colour temperature of 5080 K was successfully achieved. This work provided new insights into the design and development of color-tunable phosphors for white LEDs.

Nowadays, the development of phosphors with excellent luminescent thermal stability for various applications has become a research hotspot. Therefore, the Dy 3+ /Sm 3+ co-activated multifunctional NaYTiO 4 phosphors with excellent comprehensive performance in the field of non-contact optical measurement and white LED solid-state lighting were reported in this paper, and their crystal structure, elemental composition, optical bandgap and photoluminescence properties were systematically studied. Remarkably, the reason why NaYTiO 4 :Dy 3+ ,Sm 3+ phosphors achieved color-controlled emission from yellow to orange-red and even to white at the excitation wavelength of 363 nm was not based on the energy transfer process from Dy 3+ to Sm 3+ but on co-excitation. When the temperature reached 475 K, the luminescence intensity of the phosphor still maintained 96.75% of the initial intensity, demonstrating excellent thermal quenching property. Furthermore, the temperature sensing performance was evaluated by FIR technique according to the differential decreasing trend of Dy 3+ and Sm 3+ emission intensity with increasing temperature. Finally, we also certified the applicability of NaYTiO 4 :Dy 3+ ,Sm 3+ phosphors in white LEDs for indoor health lighting. These results indicate that NaYTiO 4 :Dy 3+ ,Sm 3+ multifunctional phosphors are promising dual functional luminescent platforms that can be used for non-contact optical thermometers and white LED device applications.

A series of Ca 3 Y(GaO) 3 (BO 3 ) 4 :Tb 3+ ,Eu 3+ phosphors were prepared by a high-temperature solid-state reaction. Their phase structures were confirmed by powder X-ray diffraction and the element distribution was measured using transmission electron microscopy elemental mapping. The photoluminescence emission and excitation spectra and fluorescence lifetime were studied and discussed in detail. The results revealed that Eu 3+ ions can be efficiently sensitized by Tb 3+ ions under near-UV excitation. In addition, the energy transfer efficiency can be controlled by adjusting the ratio of Eu 3+ and Tb 3+ to realize colour tunable emission from green to red. For Ca 3 Y(GaO) 3 (BO 3 ) 4 :0.50Tb 3+ ,0.10Eu 3+ , the emission intensity at 425 K is 78.11% of that at 300 K, being available to near-UV LEDs.