Search

The novel orange‐red light‐emitting garnet‐type phosphors Li3Bi3Te2O12:xSm3+ (0.005 ≤ x ≤ 0.25) were first synthesized using the high‐temperature solid‐state reaction method. The phase structure was recorded with XRD. Raman spectroscopic analysis was conducted for the first time to extract detailed structural insights of the tellurate garnet Li3Bi3Te2O12:Sm3+. The characteristics of the obtained compounds were investigated, including particle morphology, elemental mapping, diffuse reflection spectra, excitation and emission spectra, thermal stability, chromaticity coordinates according to the Commission International del′Eclairage, and color purity. The Li3Bi3Te2O12:Sm3+ phosphor could be effectively excited by 406 nm irradiation, and four sharp peaks were presented. The dominant peaks are located at 613 and 653 nm, corresponding to the typical transition of Sm3+ ions at 4G5/2→6H7/2 and 4G5/2→6H9/2, respectively. The phosphors present a regular concentration quenching trend, with an optimum Sm3+ doping concentration of 0.02. Impressively, the product demonstrates remarkable thermal stability by maintaining an emission intensity of 93% at a working temperature of 423 K. Additionally, the thermal quenching temperature (T0.5) surpasses 480 K. The lighting performance of the white light‐emitting diode fabricated using Li3Bi3Te2O12:0.02Sm3+ phosphor has been found to be exceptional, characterized by a high color rendering index (Ra = 90) and a low correlated color temperature (CCT = 5122 K). The electroluminescent spectrum of the red light‐emitting diode device fabricated by Li3Bi3Te2O12:0.02Sm3+ overlapped well with the absorption spectra of the phytochromes, suggesting its potential for plant cultivation light source. In conclusion, considering all these photoluminescent properties mentioned above, Li3Bi3Te2O12:Sm3+ phosphor can be regarded as a promising material for daily illumination and plant cultivation LEDs. [ABSTRACT FROM AUTHOR]

A sequence of reddish‐orange emitting NaSrBi(1−x)TeO6:xSm3+ phosphors were successfully composited by a favorable solid‐phase chemical process. The sintering temperature is optimized as 850°C. NaSrBiTeO6 (NSBTO):Sm3+ samples were assigned to the cubic double‐perovskite structure, exhibiting the space group of Fm3¯$\bar{3}$m (225). Photoluminescence emission spectra display the main peaks at 562, 598, 645, and 705 nm at 404 nm excitation. Among them, the most intense emission peak is at 645 nm. The concentration‐quenching mechanism of Sm3+ follows the interaction between electric dipoles and quadrupoles. The asymmetric ratio (I(4G5/2‐6H9/2)/I(4G5/2‐6H5/2) of NSBTO:2 mol%Sm3+ phosphor is extracted as 4.96. The optimum NSBTO:2 mol%Sm3+ phosphor has excellent thermal stability with a remained emission intensity riches 93.61% (420 K). After testing with high‐pressure water steam at various periods, the phosphor remains chemically stable for moisture resistance. For the NSBTO:2 mol%Sm3+ phosphor, the satisfactory color purity and low correlated color temperature (CCT) are obtained with 99.9% and 1494 K, respectively. The electroluminescence spectra of the prepared red light emitting diode (LED) are in conformity with the phytochrome absorption spectra of chlorophyll a, chlorophyll b, PFR, and PR. The white light‐emitting diode (w‐LED) is also perfectly packaged, obtaining an efficient color rendering index (Ra) of 92.12 and CCT of 5553 K. These exceeding optical properties certified that NaSrBi(1−x)TeO6:xSm3+ demonstrates promising prospects and can be efficiently applied in horticultural LED applications. [ABSTRACT FROM AUTHOR]

In this study, novel layered niobate KCa 2 Nb 3 O 10 :Sm3+ orange red phosphors have been successfully prepared by adopting the molten-salt method. The phase purity, surface morphology, photoluminescence properties, thermal stability, and fluorescence lifetime are systematically demonstrated. The X-ray diffraction (XRD) analysis revealed that these powders were pure phase and crystallized in an orthorhombic with a space group of Cmcm (No.63). Under 407 nm excitation, the KCa 2 Nb 3 O 10 :Sm3+ phosphors have the strongest emission peak at 603 nm which can be put down to the 6H 5/2 → 4F 7/2 transition of Sm3+. The optimum concentration of KCa 2 Nb 3 O 10 : x Sm3+ is 5 mol%. The KCa 2 Nb 3 O 10 :Sm3+ phosphors display excellent thermostability because of their high T 0.5 (over 480 K). Meanwhile, these samples show a high color purity from 96.6 to 98.2%. The white light-emitting diodes (w-LEDs) have been prepared with flying colors. All the results indicated that the potential application of the new kind of KCa 2 Nb 3 O 10 :Sm3+ luminescent powder in w-LEDs. • The KCa 2 Nb 3 O 10 :Sm3+ phosphors show a good energy transfer. • The KCa 2 Nb 3 O 10 :Sm3+ phosphors have excellent thermal stability (E a = 0.17 eV). • The synthesized phosphors exhibit the superior color purity (98.2%). • The fabricated w-LED exhibits a high color rendering index (R a = 90). [ABSTRACT FROM AUTHOR]

Novel apatite-type NaCa 3 Bi(PO 4) 3 F: x Sm3+ (0.01 ≤ x ≤ 0.30) orange-red-light phosphors were synthesized through the solid-state method at high temperature. The crystal structure, energy band structure, density of state, phase purity, particle morphology, photoluminescence properties, thermostability, and luminescence decay of the phosphors were comprehensively characterized. When λ ex = 404 nm, the optimal NaCa 3 Bi(PO 4) 3 F:0.05 S m3+ phosphor showed the orange-red emission (597 nm). The NaCa 3 Bi(PO 4) 3 F:Sm3+ phosphors exhibited abnormal thermal quenching properties as their emission intensity increased by about 2.57% from 300 to 380 K. Their intensity at 440 K was still 1.01-fold stronger than that at room temperature. The abnormal thermal quenching mechanisms were well explained via the coordinate configuration scheme. The thermal activation energy (E a) was calculated to be 0.79 eV. The color purity of all the phosphors reached 99.9%. Ultimately, a white light-emitting diode (w-LED) was fabricated based on the tri-color RGB method. The color rendering index and the chromaticity coordinates of the fabricated w-LED were 89 and (0.310, 0.319), respectively. Thus, these high thermostability NaCa 3 Bi(PO 4) 3 F:Sm3+ orange-red phosphors can be potentially used in w-LED applications. [ABSTRACT FROM AUTHOR]