Ln2+ stabilization in strontium borates

The effect of crystal structure on the stability of Ln²⁺ ions in strontium borates has been studied by luminescence spectroscopy. The results indicate that the stability of Ln²⁺ in strontium borates depends on the nature of the borate anions surrounding it and the effectiveness of the compensation of the charge on Ln³⁺, which can be quantified by the formal volume per oxygen atom, V _O, in the structure of the borate.     

Phosphors based on NaZr2(PO4)3-type calcium and strontium phosphates activated with Eu2+ and Sm3+

Ca_0.5Zr₂(PO₄)₃:Eu²⁺, Sr_0.5Zr₂(PO₄)₃:Eu²⁺, and Ca_0.5Zr₂(PO₄)₃:Eu²⁺, Sm³⁺ orthophosphates prepared through precipitation using sol-gel processes are analogs of NaZr₂(PO₄)₃ (NZP) and crystallize in space group R $\bar 3$ . Their crystallographic parameters determined by X-ray diffraction are consistent with the interatomic distances extracted from EXAFS data. Their luminescence spectra obtained under excitation in the range 300?C400 nm contain emission bands between 425 and 525 nm. Substitution of the larger sized cations Eu²⁺ and Sm³⁺ for Ca²⁺ shifts the emission bands to shorter wavelengths and reduces their width because of the decrease in the effect of the crystal field. Analysis of the spectra indicates that Eu²⁺ occupies two types of crystallographic sites (independent interstitial sites of different sizes and shapes in the NZP framework structure). Codoping with Eu and Sm has ensured luminescence with chromaticity coordinates approaching those of white light: (x = 0.27, y = 0.34).     

Eu2+在多铝酸钠体系中的发光

应用高温固相法合成了Na的多铝酸盐,并研究了Eu^2＋在体系中的发光性能．结果表明,Na_1＋xMgAl_11－xO₁₇体系在整个组成范围内保持Na的β－Al₂O₃结构不变,而对于Na_1．67－2xBa_xAl1_0．33O₁₇体系,在x＝0．30附近体系结构发生转变,x＜0．30,体系形成Na的外β－Al2O3结构的固溶体,x＞0．30,体系形成Ba的β－Al₂O₃结构的有序体;与体系组成和结构的变化相对应,Eu^2＋的发射能量和发光强度产生相应的变化,在Na的β－Al₂O₃中Eu^2＋存在高、低能两种发射中心;通过系列化研究,获得了新的组成的、具有β－Al₂O₃结构的荧光体Na_0．67Ba_0．50Mg_0．67Al_10．33O₁₇：Eu^2＋,在较低的掺杂浓度（0．05mol）下可以产生较强的发光．     

Luminescence of Eu2+ in Barium Octoborate

The luminescence of Eu2+ in low- and high-temperature modified BaB8O13 are reported. The valance change from Eu3+ to Eu2+ is observed when the samples are prepared in air. Eu2+ shows f-d transition at room temperature under UV excitation. The temperature dependency of the emission of Eu2+ in the hosts is studied. Multiple crystallographic sites for Eu2+ in the lattice are observed.     

Luminescence of Eu2+ in Barium Octoborat

The luminescences of Eu2+ in low- and high-temperature modified BaB8O13 are reported. The valance change from Eu3+ to Eu2+ is observed when the samples are prepared in air. Eu2+ shows f-d transition at room temperature under UV excitation. The temperature dependency of the emission of Eu2+ in the hosts is studied. Multiple crystallographic sites for Eu2+ in the lattice are observed.     

Luminescence and energy transfer of Sm3+/Eu3+ co-doped transparent glass ceramics

Journal of Materials Science: Materials in Electronics - The Sm3+/Eu3+ doped transparent glass ceramics (GCs) containing Na7.15(Al7.2Si8.8O32) crystallite were successfully prepared by melt...     

Sm3+ photoluminescence in co-sputtered SiO2 thin films

Thin films of SiO₂ containing Sm were deposited by magnetron co-sputtering. The concentration of Sm in the films was varied by changing the amount of Sm placed on the fused silica target. The samarium content in the films was established by Rutherford back-scattering measurements. Photoluminescence (PL) was excited with the 488-nm line of an Ar ion laser. It consists of several lines in the visible, which are assigned to transitions between multiplets of Sm³⁺. The concentration dependence of the PL intensity was studied. It passes through a maximum and decreases at higher Sm content. The films were annealed in vacuum at temperatures between 300 and 1000 °C. There was a strong increase in the PL intensity after annealing at 600 °C, and then it fell again after annealing at 1000 °C. The data are compared to spectra of Sm³⁺ in other matrices. The mechanisms of PL excitation and quenching are discussed.     

Luminescence enhancing encapsulation for strontium aluminate phosphors with phosphate

SrAl₂O₄:Eu²⁺,Dy³⁺ phosphors are chemically unstable against water. An encapsulation on the phosphors by direct reactions between triethyl phosphate and strontium aluminate was reported in this paper. Powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), thermogravimetric (TG) analysis, water resistance measurements, and photoluminescence (PL) spectrophotometry were used to characterize the phosphors before and after encapsulation. Experimental results showed that products of encapsulation reactions under an appropriate condition were in shape of nano-films on the phosphors. These thin films could effectively enhance both water resistance and photoluminescence of the phosphors.     

VUV sensitization of Mn2+ emission by Tb3+ in strontium aluminate phosphor

The luminescence properties of green emitting strontium aluminate phosphor SrAl₁₂O₁₉ doped and co-doped with Mn²⁺ and Tb³⁺ were studied using synchrotron radiation. It is shown that Tb³⁺, exhibiting a strong absorption band in the vacuum-ultraviolet (VUV), provides sensitisation of Mn²⁺ emission in this host. The observed sensitisation effect of the Tb–Mn pair can be used for improving the efficiency of VUV phosphors.     

Eu2+在多铝酸钠体系中的发光

应用高温固相法合成了Ｎａ的多铝酸盐,并研究了Ｅｕ＾２＋在体系中的发光性能,结果表明,Ｎａ１＋ｘＭｇＡｌ１１－ｘＯ１７体系在整个组成范围内保持Ｎａ的β－Ａｌ２Ｏ３结构不变,而对于Ｎａ１．６７－２ｘＢａｘＡｌ１０．３３Ｏ１７体系,在ｘ＝０．３０附近体系结构发生转变,ｘ〈０．３０,体系形成Ｎ的β－Ａｌ２Ｏ３结构的固溶体,ｘ〉０．３０,体系形成Ｂａ的β－Ａｌ２Ｏ３结构的有序体;与体系组成的和结构的变化相对     

Eu2+离子在Sr2Al6O11基磷光体中发光行为的研究

研究了不同Eu掺杂浓度对Sr₂Al₆O₁₁基磷光体发光性能的影响.结果发现,当Eu掺杂浓度低于0.01mol时,在其发射光谱中存在403和493nm的主发射峰,对应着Sr₂Al₆O₁₁基质中Sr的两种不同位置Sr1和Sr2位.随着Eu掺杂浓度增加,由于能量传递作用,导致403nm的发射峰消失,493nm的发射峰增强.余辉衰减曲线表明,未掺杂Dy的磷光体没有余辉性能,当Eu掺杂量在0.01mol时,余辉性能最好.进一步提高Eu的掺杂量,由于浓度猝灭作用,导致发光性能下降.     

碘化铯晶体中Pb2+基聚集相的发光性质

掺铅的碘化铯（Pb：CsI）晶体在400℃空气中进行热处理可以在晶体中诱导产生发光中心,这些发光中心的激发谱与CS－Pb-I体系中一系列化合物的激子吸收谱相吻合．它们被认为是由该晶体在退火过程中所形成的CsPbI3、Cs4PbI6等聚集相产生的．测量了10～30K温度范围内分别在410nm和360nm波长激发下Ph：CsI的发射谱,观察到各发射谱的相对强度随退火时间而变化,这表明在400℃退火温度下晶体中各类Cs－Ph－I聚集相的形成和转化已十分活跃．     

Luminescence enhancement of Tb3+ in Sr3SiO5:Eu2+ phosphor

Sr₃SiO₅ phosphors co-doped with Eu²⁺ and Tb³⁺ were prepared by a conventional solid-state reaction method. The prepared Sr₃SiO₅:Eu²⁺,Tb³⁺,Li⁺ phosphors had characteristic luminescent spectra excited under near-UV excitation in which both the broadband spectrum assigned to Eu²⁺ and the line spectrum assigned to Tb³⁺ are observed, although Tb³⁺ is inactive with this photon energy in general. For Eu²⁺–Tb³⁺ codoped Sr₃SiO₅, energy transfer process takes place and the mechanism is ascribed to the overlap between the shorter Eu²⁺ luminescence band from the Sr₃SiO₅ crystal structure with two Sr sites and ₅D⁴ energy level of Tb³⁺ ion. Due to the energy transfer, PL intensity of Eu²⁺ emission increased about 26 %. We suggest that this enhancement mechanism could shed light on the potential applications in white light-emitting diodes excited by near-UV light. In addition, the emission peak position near the orange region indicates that our system is a step towards a new class of wavelength sources for artificial lighting with improved PL intensity and lower energy consumption.     

Luminescence Spectra of Am3+ in Cs2NaLuBr6:Am3+ Bromoelpasolite

Luminescence spectra of the cubic crystal of Cs₂NaLuBr₆:Am³⁺ (2.5 mol % ²⁴³Am) were studied in the region of the (² G ₂, ⁵ D ₂) ⁷ F ₀ (460-490 nm) and ⁵ L ₆ ⁷ F ₀ (510-540 nm) transitions in the range from room temperature to 12 K. From the analysis of the vibronic pattern of the spectra, the zero-phonon 0-0 transitions forbidden for the O _h symmetry were localized, and the first data on the splitting sublevels of the actinide element (Am³⁺, 5f ⁶) in the field of the ideal octahedron of the AmBr₆ ^3- type were obtained. It was found that in the wavelength ranges indicated, the crystal studied exhibits a fairly strong self-luminescence due to the -decay energy of ²⁴³Am.     

Luminescence properties of SnO2 nanoparticles dispersed in Eu3+ doped SiO2 matrix

SnO2 nanoparticles dispersed in Eu3+ doped silica (SnO2-SiO2:Eu3+) were prepared at a low temperature (185 degrees C) in ethylene glycol medium. Transmission electron microscopy studies on as-prepared samples have established that SnO2 nanoparticles having size of 4.6 nm are uniformly covered by the SiO2 matrix. Significant extent of exciton mediated energy transfer between SnO2 and Eu3+ ions in heat treated SnO2-SiO2:Eu3+ samples has been attributed to the diffusion of Eu3+ ions from the SiO2 matrix to the near vicinity of SnO2 nanoparticles and its incorporation in the SnO2 matrix. On the other hand, very weak energy transfer exists for SnO2:Eu3+ nanoparticles heated at different temperatures due to the phase segregation of Eu3+ ions from the matrix.     

Effect of La3+ Doping on the Luminescence of BaSi2O2N2 : Eu2+ Phosphors

研究了L3+掺杂对BaSi2O2N2∶Eu2+发光性能的影响.通过高温固相反应制备了纯相的Ba0.94-Si2O2N2∶0.06Eu2+荧光粉.在此基础上进行La3+的掺杂,并对少量La3+掺杂的LaxBa0.94-1.5xSi2O2N2∶0.06Eu2+荧光粉的结构和光学性能进行了研究.XRD图谱表明粉体在低掺杂时保持了基质BaSi2O2N2的晶格结构.通过共掺x=0.035的La3+可使荧光粉的发光效率提高到157％,原因是La3+部分取代Ba12+产生了阳离子缺陷,其可以吸收光源能量并将能量传递给Eu2+.最终这些能量通过Eu2+的4f65d→4f7跃迁以光辐射的形式释放出来.