Composition Screening in Blue-Emitting Li4Sr1+xCa0.97–x(SiO4)2:Ce3+ Phosphors for High Quantum Efficiency and Thermally Stable Photoluminescence

A series of novel red‐emitting Ca8ZnLa1−xEux(PO4)7 phosphors were successfully synthesized using the high‐temperature solid‐state reaction method. The crystal structure, photoluminescence spectra, thermal stability, and quantum efficiency of the phosphors were investigated as a function of Eu3+ concentration. Detailed analysis of their structural properties revealed that all the phosphors could be assigned as whitlockite‐type β‐Ca3(PO4)2 structures. Both the PL emission spectra and decay curves suggest that emission intensity is largely dependent on Eu3+ concentration, with no quenching as the Eu3+ concentration approaches 100%. A dominant red emission band centered at 611 nm indicates that Eu3+ occupies a low symmetry sites within the Ca8ZnLa(PO4)7 host lattice, which was confirm by Judd‐Ofelt theory. Ca8ZnLa1−xEux(PO4)7 phosphors exhibited good color coordinates (0.6516, 0.3480), high color purity (~96.3%), and high quantum efficiency (~78%). Temperature‐dependent emission spectra showed that the phosphors possessed good thermal stability. A white light‐emitting diode (LED) device were fabricated by integrating a mixture of obtained phosphors, commercial green‐emitting and blue‐emitting phosphors into a near‐ultraviolet LED chip. The fabricated white LED device emits glaring white light with high color rendering index (83.9) and proper correlated color temperature (5570 K). These results demonstrate that the Ca8ZnLa1−xEux(PO4)7 phosphors are a promising candidate for solid‐state lighting.

Section: Photoluminescence Propertiesmentioning

confidence: 96%

Section: Structure Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A novel dazzling Eu³⁺‐doped whitlockite‐type phosphate red‐emitting phosphor for white light‐emitting diodes

Tang

Zheng

et al. 2018

“…As we have seen, the Mn 4+ emission ( 2 E g – 4 A 2g ) in the Sr 4− x Ba x Al 14 O 25 host more be closer to a single exponential fitting equation. Therefore, the lifetime could be estimated to equation representing below:

I = I_{0} \times \exp (\frac{- t}{τ})

where, the I and I 0 represent the emission intensity at times t and 0, respectively; the t as well as the varying time; the τ is the fluorescence lifetimes. As above‐mentioned, the fluorescence lifetimes a series of Sr 4− x Ba x Al 13.99 O 25 :0.01Mn 4+ phosphors could be calculated to 1.259, 1.277, 1.298, 1.282, and 1.264 ms when the x = 0, 0.05, 0.10, 0.15, and 0.20, respectively.…”

Section: Resultsmentioning

confidence: 99%

Enhancing photoluminescence properties of Mn⁴⁺‐activated Sr₄₋_xBa_xAl₁₄O₂₅ red phosphors for plant cultivation LEDs

Yang

Gai

et al. 2019

Non–rare earth Mn4+‐activated strontium aluminate phosphor is considered to be a promising material for plant cultivation field owing to their advantage of inexpensively, environment friendly, nontoxic, and appropriate spectral range. In this paper, a Sr4−xBaxAl13.99O25:0.01Mn4+,1.4H3BO3 strontium aluminate phosphor is synthesized by a convenient high‐temperature solid‐state reaction. The photoluminescence spectra located at red region with a peak at 655 nm in the range of 600 to 750 nm that can be excited under the excitation of ultraviolet (~346 nm) or blue light (~450 nm). The shape emission band at 655 nm is attributed to the transition of 2Eg‐4A2g. Furthermore, the emission intensity of Sr4−xBaxAl13.99O25: 0.01Mn4+,1.4H3BO3 phosphor is conducted in detail with the variety of Ba2+ doping concentration and the intensity can be enhanced to 140.9% than the Sr4Al13.99O25:0.01Mn4+,1.4H3BO3 when the value of Ba2+ concentration equal to 0.1 mol. In addition, the X‐ray diffraction spectra, element mapping, composition modifying, optical properties, FT‐IR spectra, diffuse reflectance spectra, thermal stability, and fluorescence lifetime are systematically investigated. According to the electro‐luminescent spectra of as‐packaged LED, indicating that the Sr3.9Ba0.1Al13.99O25:0.01Mn4+,1.4H3BO3 phosphor will become a great candidate for plant cultivation LEDs due to the emission spectra match well the plant pigment spectrum.

“…Obviously, radiation reabsorption and exchange coupling are not the main working factors in this study. In order to figure out the exact mechanism of concentration quenching, the critical energy‐transfer distance R c has been calculated according to the relationship given by Blasse:

R_{c} \approx 2 {(][, \frac{3 V}{4 π χ_{c} N})}^{1 / 3}

where V , χ c , and N represent the volume of the unit cell, the critical concentration of the Ti 4+ ions, and the number of host cations in the unit cell, respectively. For the present CAZO:4%Ti 4+ phosphors, V = 922.77 Å 3 , χ c = 0.04, and N = 4.…”

Section: Resultsmentioning

confidence: 99%

Exploration of bluish violet‐emitting phosphor Ca₃Al₄ZnO₁₀:Ti⁴⁺ with enhanced emission by Ca²⁺ vacancies

Zhou

et al. 2018

In this paper, we introduced a bluish violet‐emitting phosphor Ca3Al4ZnO10:Ti (IV) (CAZO:Ti4+) synthesized by high‐temperature solid‐state reaction. Upon 265 nm excitation, a broad emission band spanned from 300 nm to 500 nm and centered at 370 nm was observed. In addition, the effects of flux and charge compensation to photoluminescence properties of CAZO:Ti4+ were systematically investigated. The results show that 103% improvement of emission intensity was achieved when 1% H3BO3 flux was introduced and 32.8% enhancement of it for 2% Ca2+ vacancies doped as charge compensator. Moreover, the lifetimes, band gap energy, concentration quenching mechanism, as well as electron transition process of CAZO:Ti4+ were discussed. Due to the efficient broad bluish violet emission, this phosphor may find a potential application in mercury vapor‐excited fluorescent lamp for plant growth.