Tunable luminescence from Eu3+ and Ce3+ doped/co-doped color tunable Na4Ca(PO3)6 phosphors for white LEDs and solar cell applications

Journal of Materials Science: Materials in Electronics - In recent years, the invention of white light by combining red, green and blue (RGB) phosphors with near-ultraviolet (NUV) chips has been...     

Visible quantum cutting through downconversion in Eu3+-doped K2GdZr(PO4)3 phosphor

K₂Gd_1?xZr(PO₄)₃:Eu_x³⁺ (0.02 ≤ x ≤ 0.1, x is in mol.%) were prepared by solid-state reaction method and their photoluminescence properties were investigated in ultra-violet (UV) and vacuum ultra-violet (VUV) region. The phenomenon of visible quantum cutting through downconversion was observed for the Gd³⁺–Eu³⁺ couple in this Eu³⁺-doped K₂GdZr(PO₄)₃ system. Visible quantum cutting, the emission of two visible light photons per absorbed VUV photon, occurred upon the 186 nm excitation of Gd³⁺ at the ⁶G_J level via two-step energy transfer from Gd³⁺ to Eu³⁺ by cross-relaxation and sequential transfer of the remaining excitation energy. The results revealed that the efficiency of the energy transfer process from Gd³⁺ to Eu³⁺ in the Eu³⁺-doped K₂GdZr(PO₄)₃ system could reach to 155% and K₂GdZr(PO₄)₃:Eu³⁺ was effective quantum cutting material.     

红色荧光粉Ca_9Al(Po_4)_7:Eu~(3+)的制备与发光特性

本文采用高温固相法合成了Ca9Al(Po4)7:Eu3+红色荧光粉,并对其发光特性进行了研究。该荧光粉在350nm-410nm有一个宽带激发峰,适用于UVLED管芯的激发;在紫外激发下的发射峰由位于589nm和593nm,612nm、616nm和619nm,654nm及688nm四组线状峰构成,分别对应于Eu3+的(5D0～7F1)、(5D0～7F2)、(5D0～7F3)及(5D0～7F4)特征跃迁,呈现红色发光。探讨了掺杂的Eu3+浓度对样品发光强度的影响,其最佳掺杂浓度为5%。研究了其自身浓度猝灭机理,为电偶极-电四极相互作用。发现不同电荷补偿剂Li+,Na+,K+的引入均能使发光强度得到提高,尤其以Li+最佳,发光强度提高了大约35%。结果表明,Ca9Al(Po4)7:Eu3+是一种适用于UVLED管芯激发的用于白光LED的红色荧光粉。     

Ca10K（PO4）7:Eu3+红色荧光粉的制备及其发光性质

高温固相法合成了Ca10-xK(PO4)7:xEu3+(x=0.02,0.04,0.06,0.08,0.10,0.12,0.14和0.16)的红色荧光粉。X射线衍射表明,样品具有标准的Ca10K(PO4)7六角晶体结构,且无第二相存在。在393nm的波长激发下,样品获得由Eu3+的4f-4f跃迁产生红光发射,其中以613nm附近的5 D0→7F2电偶极跃迁发射为最强。通过调节Eu3+的掺杂浓度,获得了色坐标与商业化Y2O2S:Eu3+荧光粉十分接近的接近纯色的红色荧光粉。Ca10K(PO4)7:Eu3+是一种可望应用于紫外激发的白光LED的红色荧光粉。     

Synthesis and photoluminescence properties of a cyan-emitting phosphor Ca3(PO4)2:Eu2+ for white light-emitting diodes

In this paper, a cyan-emitting phosphor Ca₃(PO₄)₂:Eu²⁺ (TCP:Eu²⁺) was synthesized and evaluated as a candidate for white light emitting diodes (WLEDs). This phosphor shows strong and broad absorption in 250–450 nm region, but the emission spectrum is prominent at around 480 nm. The emission intensity of the TCP:Eu²⁺ was found to be 60% and 82% of that of the commercial BaMgAl₁₀O₁₇:Eu²⁺ (BAM) under excitation at 340 nm and 370 nm, respectively. Upon excitation at 370 nm, the absolute internal and external quantum efficiencies of the Ca₃(PO₄)₂:1.5%Eu²⁺ are 60% and 42%, respectively. Moreover, a white LED lamp was fabricated by coating TCP:Eu²⁺ with a blue-emitting BAM and a red-emitting CaAlSiN₃:Eu²⁺ on a near-ultraviolet (375 nm) LED chip, driven by a 350 mA forward bias current, and it produces an intense white light with a color rendering index of 75.     

Comparative study of Ca3Bi(PO4)3:Eu3+ phosphors prepared by three methods

Ca₃Bi(PO₄)₃:Eu³⁺ phosphors were synthesized by solid-state (SS) reaction, co-precipitation (CP) and sol–gel methods. The resulting phosphors were well characterized by X-ray diffraction, field-emission scanning electron microscopy and photoluminescence spectra. The X-ray diffraction results suggested that the pure phase of Ca₃Bi(PO₄)₃:Eu³⁺ can be obtained by SS reaction and CP method. The phosphors obtained by CP method showed more homogeneous, agglomerate-free particles. The samples obtained by the CP method showed the highest emission intensity among the three methods which fired at 1,000 °C for 2 h. It was showed that the CP method was the most respected process for the preparation of Ca₃Bi(PO₄)₃:Eu³⁺ phosphors.     

BaMg2(PO4)2:Sm3+红色荧光粉发光性质的研究

采用高温固相法合成了BaNg2(PO4)2:Sm3+红色荧光材料发光材料并对其发光特性进行了研究.该荧光粉有三个主要发射峰,分别位于564 nm、600 nm、648 nm,对应于4G5/2→6H5、4G5/2→6H7、4G5/2→6H9/2的跃迁发射,其中600 nm处发射最强,呈现红色发光.随着Sm3+浓度的增加,...     

Luminescence properties of Eu2+-activated Sr5(PO4)2(SiO4) for green-emitting phosphor

A green-emitting phosphor of Eu²⁺-activated Sr₅(PO₄)₂(SiO₄) was synthesized by the conventional solid-state reaction. It was characterized by photoluminescence excitation and emission spectra, and lifetimes. In Sr₅(PO₄)₂(SiO₄):Eu²⁺, there are at least two distinguishable Eu²⁺ sites, which result in one broad emission situating at about 495 nm and 560 nm. The phosphor can be efficiently excited in the wavelength range of 250–440 nm where the near UV (～ 395 nm) Ga(In)N LED is well matched. The dependence of luminescence intensities on temperature was investigated. With the increasing of temperature, the luminescence of the phosphor shows good thermal stability and stable color chromaticity. The luminescence characteristics indicate that this phosphor has a potential application as a white light emitting diode phosphor.     

Photoluminescence and quenching study of the Sm3+-doped LiBaPO4 phosphor

Journal of Materials Science: Materials in Electronics - Sm3+-doped LiBaPO4 phosphors have been successfully synthesized by solution combustion method. As prepared samples were characterized by...     

绿色荧光粉Zn_2Ca(PO_4)_2:Tb~(3+)的制备及发光性能研究

采用高温固相法合成了绿色荧光粉Zn2Ca(PO4)2:Tb3+,测定了该荧光粉的XRD图谱、激发光谱及发射光谱。XRD图谱表明在高温还原气氛下合成了纯相的荧光粉Zn2Ca(PO4)2:Tb3+。该荧光粉的激发谱位于340～400nm。在紫外激发下主要发射峰位于490、544、584、622nm,对应于Tb3+的5D4→7F6、5D4→7F5、5D4→7F4、5D4→7F3的特征发射。考察了Tb3+的掺杂浓度对样品发光效率的影响,分析了Tb3+的544nm发射的自身浓度猝灭机理并探讨了敏化剂Ce3+离子的加入对荧光粉发光的影响。此绿色荧光粉Zn2Ca(PO4)2:Tb3+是一种很有潜力的适于UVLED管芯激发的发光粉。     

Emission analysis of Sm3+:Ca4GdO(BO3)3 powder phosphor

This paper reports on the spectral analysis of reddish orange color luminescent Sm³⁺:Ca₄GdO(BO₃)₃ powder phosphor. This phosphor powder has been synthesized by a solid state reaction method. Emission spectrum of it has shown four emission transitions of ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2, 9/2, 11/2) and among them, the transition ⁴G_5/2 → ⁶H_7/2 displays the reddish orange (605 nm) color. Lifetimes of three emissions (⁴G_5/2 → ⁶H_{J=5/2, 7/2 & 9/2}) have been computed based on the measured decay curves. Besides the measurement of emission spectrum of this material, its nature and structural details have also been investigated from XRD, SEM and FTIR studies.     

Photoluminescence properties of Sr3(PO4)2: Eu2+, Dy3+ double-emitting blue phosphor for white LEDs

Double-emitting blue phosphor Sr₃(PO₄)₂: Eu²⁺, Dy³⁺ was synthesized by solid state reaction under H₂ atmosphere. XRD exhibited the pure hexagonal phase of the prepared phosphor. The photoluminescence results showed that all samples had intense broad absorption band between 250 and 450 nm, which matched well with the near-UV (350–420 nm) emission band of InGaN-based chips. The emission spectrum of Sr₃(PO₄)₂: Eu²⁺, Dy³⁺ consisted of two broad bands, peaked at 485 nm and 410 nm, which originated from two luminescent centers, related to 4f⁶5d¹ → 4f⁷ transition of Eu²⁺ in six-coordinated Sr(I) and ten-coordinated Sr(II) sites respectively. The intensity ratio of two emission bands could be easily tuned by adjusting Dy³⁺ co-doping content, which resulted in color-tunable luminescence in bluish green region to purplish blue region.     

Luminescence properties of long-lasting phosphor SrMg2(PO4)2:Eu2+, Ho3+, Zr4+

Novel long lasting phosphors SrMg₂(PO₄)₂:Eu²⁺, SrMg₂(PO₄)₂:Eu²⁺, Zr⁴⁺, SrMg₂(PO₄)₂:Eu²⁺, Ho³⁺ and SrMg₂(PO₄)₂:Eu²⁺, Ho³⁺, Zr⁴⁺ were synthesized by conventional solid-state reaction method. The luminescent properties were systematically characterized by X-ray diffraction, photoluminescent excitation and emission spectra, as well as thermoluminescence spectrum and decay curves. The XRD patterns indicated that the samples belonged to monoclinic phase and co-doping Eu²⁺, Ho³⁺ and Zr⁴⁺ ions had no effect on the basic crystal structure. These phosphors emitting purplish blue light is related to the characteristic emission of Eu²⁺. The afterglow time of Eu²⁺ activated SrMg₂(PO₄)₂ can be greatly enhanced by the co-doping of Ho³⁺, Zr⁴⁺. After the 365 nm UV light excitation source switching off, the Sr_0.92Mg_1.95(PO₄)₂:Eu²⁺_0.01, Zr⁴⁺_0.05, Ho³⁺_0.07 phosphorescence can be observed for more than 1013 s in the limit of light perception of dark-adapted human eyes (0.32 mcd/m²). Different kinds of TL peaks at 423, 448 and 473 K have appeared, and traps densities have increased compared with the Eu²⁺ single doped SrMg₂(PO₄)₂ phosphor. By analyzing the TL curve the depths of traps were calculated to be 0.846, 0.896 and 0.946 eV, respectively, which suggested that the co-doping of Ho³⁺, Zr⁴⁺ improved the electron storage ability of material. Besides, the mechanism was discussed in this report.     

Ca3(PO4)2:Er3+,Yb3+: An upconversion phosphor for in vivo imaging

Using a sol-gel process, we have synthesized compounds isostructural with the biogenic mineral whitlockite and containing calcium phosphate, β-Ca₃(PO₄)₂, codoped with Er³⁺ and Yb³⁺ in various concentrations and ratios. Their particle size was determined to be ～42–57 nm by atomic force microscopy and ～93 nm by dynamic light scattering. The particles were shown to be weak anion exchangers (their zeta potential is ?13.3 mV). The observed luminescence of the β-Ca₃(PO₄)₂:Er³⁺,Yb³⁺ phosphates in the visible spectral region (λ = 0.525, 0.550, and 0.650 μm) under IR excitation (λ = 0.98 μm) is due to the upconversion mechanism and is acceptable for in vivo imaging in terms of safety (green emission) and intensity. Biocompatibility testing results demonstrate that the β-Ca₃(PO₄)₂:Er³⁺,Yb³⁺ phosphates meet the relevant biosafety and nontoxicity criteria.