The Preparation and Optical Properties of Novel LiLa(MoO4)2:Sm3+,Eu3+ Red Phosphor

Abstract

Novel LiLa1−x−y(MoO4)2:xSm3+,yEu3+ (in short: LL1−x−yM:xSm3+,yEu3+) double molybdate red phosphors were synthesized by a solid-state reaction at as low temperature as 610 °C. The optimal doping concentration of Sm3+ in LiLa1−x(MoO4)2:xSm3+ (LL1−xM:xSm3+) phosphor is x = 0.05 and higher concentrations lead to emission quenching by the electric dipole—electric dipole mechanism. In the samples co-doped with Eu3+ ions, the absorption spectrum in the near ultraviolet and blue regions became broader and stronger than these of the Sm3+ single-doped samples. The efficient energy transfer from Sm3+ to Eu3+ was found and the energy transfer efficiency was calculated. Under the excitation at 403 nm, the chromaticity coordinates of LL0.95−yM:0.05Sm3+,yEu3+ approach to the NTSC standard values (0.670, 0.330) continuously with increasing Eu3+ doping concentration. The phosphor exhibits high luminous efficiency under near UV or blue light excitation and remarkable thermal stability. At 150 °C, the integrated emission intensity of the Eu3+ remained 85% of the initial intensity at room temperature and the activation energy is calculated to be 0.254 eV. The addition of the LL0.83M:0.05Sm3+,0.12Eu3+ red phosphors can improve the color purity and reduce the correlated color temperature of WLED lamps. Hence, LL1−x−yM:xSm3+,yEu3+ is a promising WLED red phosphor.

Exploration of structural, thermal and spectroscopic properties of self-activated sulfate Eu2(SO4)3 with isolated SO4 groups

“…Among rare earth compounds, the crystals carrying Eu 3+ ions are of particular interest because the ions originate efficient red photoluminescence appropriate for the creation of WLED devices with spectral properties similar to the Sun daylight. In the recent years, the spectroscopic properties of different Eu 3+ -bearing phosphors were evaluated to see the relation between their structural and optical characteristics [22][23][24][25][26]. However, in the phosphor compounds, the Eu 3+ doping level is commonly low and, frequently, the Eu 3+ ions distribution over the appropriate crystallographic positions is not evident.…”

Evidence and Practical Applications of Site Occupancy Theory (SOT) of Eu3+ in Scheelite Compounds

“…Rare earth element is the general name of 15 elements from La (57) to Lu (71) and 17 elements with Y and Sc in the periodic table of chemical elements, whose electron configuration is [Xe]­4f n 5d m 6s 2 , and the general electron configuration of trivalent rare earth ions is [Xe]­4f n , where n = 1–14 and m = 0 or 1. ,− The excitation and emission of trivalent rare earth ions are due to the electron transition of the unfilled 4f orbital, which has two modes of transition, namely f–f transition and f–d transition. ,,, The f–f transition is a forbidden transition, the emission line is linear, the shape of the spectral line does not change with the change of temperature, good thermal stability, and rich spectral line. − The f–d transition is a permitted transition, and 5d electrons are more susceptible to the crystal field than 4f electrons. ,,, Therefore, due to the difference in the crystal field of the same ion in different substrates, the intensity and wavelength of excitation have huge differences. Taking the Eu 3+ ion as an example, the Eu 3+ ion has a 4f 6 configuration and mainly emits red light.…”

High Quantum Yield Shortwave Infrared Luminescent Tracers for Improved Sorting of Plastic Waste

“…Although the energy of optical 4f–4f transitions in Ln 3+ ions shows weak sensitivity to the environment, their radiative properties, a rate of radiative transitions and luminescence quantum yield (PLQY), are sensitive enough to the surrounding crystal field and provide plenty of opportunities for tuning when different inorganic crystal hosts are employed. Among inorganic phosphors, molybdate hosts generally have many attractive features, including easy solid-state growth and synthesis of the compounds with high Ln 3+ doping content. − Furthermore, ternary molybdates with the structural formula Li 3 Ba 2 Ln 3 (MoO 4 ) 8 have garnered considerable attention in recent years because they exhibit a large amount of structural diversity combined with outstanding thermal and chemical stability, a high degree of crystallinity, and a moderate phonon energy of approximately 1000 cm –1 . − The family of ternary cationic molybdates Li 3 Ba 2 Ln 3 (MoO 4 ) 8 was initially reported by Klevtsova et al, and Garcı́a-Cortés et al They explained that partial replacement of the Ln 3+ , Ba 2+ , and Li + cations in the ternary molybdate system makes it possible to construct a wide variety of structures with more complex compositions. In the ternary cationic molybdate system, there is no inversion center geometry at either the Ba 2+ or Gd 3+ site, which are connected by five and eight O 2– ions, respectively.…”