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δ-BiB3O6 shows a comparable nonlinear optical performance with the famous α-BiB3O6. It can be prepared either by a high temperature-high pressure method or by a sol–gel method associated with RE3+-doping (RE = La, Ce, Pr, and Nd). A direct solid state reaction at 700 °C stabilized 20 atom% La3+ doped δ-BiB3O6 compared to the previously reported record (15 atom%) in the literature. La3+ doping would not only expand the thermodynamically stable region, which is critical for the synthesis, but also hasten the crystallization process. Moreover, Eu3+, a smaller RE cation, was also doped for the first time at a high doping level (7 atom%) simply by a seed-assisted solid state reaction, which apparently provides additional functionality and will prompt further efforts on single crystal growth of RE3+-doped δ-BiB3O6 under ambient pressure. The combined powder X-ray diffraction and transmission electron microscopy analysis underpinned the phase purity and doping homogeneity of cation doped bismuth borates. UV-excited red luminescence was observed for δ-Bi0.93Eu0.07B3O6. [ABSTRACT FROM AUTHOR]

Searching efficient red phosphors under near‐UV or blue light excitation is practically important to improve the current white light‐emitting diodes (WLEDs). Eu2+‐ and Mn4+‐based red phosphors have been extensively studied. Here we proposed that Eu3+ is also a promising activator when it resides on a noncentrosymmetric coordination site. We proved that Cd4GdO(BO3)3 is a good host, which has a significantly distorted coordination for Eu3+. A careful crystallographic study was performed on the solid solutions of Cd4Gd1‐xEuxO(BO3)3 (0≤x≤1) by Rietveld refinements. The as‐doped Eu3+ cations locate at the Gd3+ site and are well separated by CdO8, CdO6 and BO3 groups; thus, only a slight concentration quenching was observed at ≈80 atom % Eu3+. Most importantly, the parity‐forbidden law of 4f‐4f transitions for Eu3+ are severely depressed, thus the absorptions at ≈393 and ≈465 nm are remarkable. Cd4Gd0.2Eu0.8O(BO3)3 can be pumped by a 395 nm LED chip to give a bright red emission, and when mixed with other commercial blue and green phosphors, it can emit the proper white light (0.3657, 0.3613) with a suitable Ra≈87 and correlated colour temperature ≈4326 K. In‐situ photoluminescence study indicated the low thermal quenching of these borate phosphors, especially under 465 nm excitation. Our case proves the practicability to develop near‐UV excited red phosphors in rare‐earth‐containing borates. [ABSTRACT FROM AUTHOR]

A series of Tb3+ and Eu3+ co-doped Ba6Bi9B79O138 (BBBO) phosphors were prepared by high-temperature solid-state reactions in order to utilize the host-sensitization effect of Bi3+. Energy transfer processes from Bi3+ in the host to both Tb3+ and Eu3+, as well as from Tb3+ to Eu3+ were proved. Under UV-excitation, three emissions can be simultaneously observed in a single-phase phosphor, including a blue band attributed to Bi3+ emission in the host, green lines due to Tb3+ transitions of 5D4→7FJ (J = 6, 5, 4, 3), and red lines due to Eu3+ transitions of 5D0→7FJ (J = 1, 2, 3, 4). Thus, the total emission could be rationally tuned by varying the relative doping contents of Tb3+/Eu3+ and by selecting appropriate exciting irradiation. Thermal stability was investigated by in situ PL spectra at elevated temperatures. It is quite interesting to observe a significant enhancement of red emission in both BBBO:0.05Eu3+ and BBBO:0.05Tb3+,0.005Eu3+ excited at 279 nm. Especially in the latter case, the red emission intensity at 150 °C is roughly 3 times that at room temperature, which is explained by the increasing efficiency of Bi3+→ Eu3+ and Tb3+→ Eu3+ energy transfer upon annealing. [ABSTRACT FROM AUTHOR]

Scheelite compounds with Eu3+ substitution are well-known red-phosphors. We prepared and performed a detailed structural characterization of A1–1.5xEux□0.5xWO4 and A0.64–0.5yEu0.24Liy□0.12–0.5yWO4 (A = Ca, Sr; □ = vacancy) to confirm the A-site vacancy mechanism for charge balance when bivalent A cations were substituted by Eu3+. All compounds crystallize in I41/a with a disordered arrangement of A2+, Eu3+, □ at the A-site. The title compounds are all good red phosphors with a high R/O ratio (∼10), indicating that Eu3+ is located at a significantly distorted cavity. A1–1.5xEux□0.5xWO4 shows a saturation phenomenon at a high doping level, x = 0.20. With the incorporation of Li+, the emission intensity was generally enhanced compared to the Li+-free samples, moreover, an increase of the Li+ content reduces the content of vacancies, resulting in further increase of the luminescence intensity. [ABSTRACT FROM AUTHOR]

Sol–gel method was applied to prepare homogenous and highly crystalline phosphors with the formulas α-GdB5O9:xTb3+ (0 ≤x≤ 1), α-Gd1−xCexB5O9 (0 ≤x≤ 0.40), α-GdB5O9:xCe3+, 0.30Tb3+ (0 ≤x≤ 0.15) and α-GdB5O9:0.20Ce3+, xTb3+ (0 ≤x≤ 0.10). The success of the syntheses was proved by the linear shrinkage or expansion of the cell volumes against the substitution contents. In α-GdB5O9:xTb3+, an efficient energy transfer from Gd3+ to Tb3+ was observed and there was no luminescence quenching. The exceptionally high efficiency of the f–f excitations of Tb3+ implies that these phosphors may be good green-emitting UV-LED phosphors. For α-Gd1−xCexB5O9, Ce3+ absorbs the majority of the energy and transfers it to Gd3+. Therefore, the co-doping of Ce3+ and Tb3+ leads to a significant enhancement in the green emission of Tb3+. Our current results together with the study on α-GdB5O9:xEu3+ in the literature indicate that α-GdB5O9 is a good phosphor host with advantages including controllable preparation, diverse cationic doping, the absence of concentration quenching, and effective energy transfer. [ABSTRACT FROM AUTHOR]

It is important to develop red phosphors which can be efficiently excited by near ultraviolet (NUV) irradiation, matching the wavelength of commercial LED chips. ZnLaB 5 O 10 possesses a significantly distorted coordination of La3+ and suitable for the Eu3+ incorporation, whose parity-forbidden law could be suppressed in such a coordination and be efficiently excited by f - f transitions in the NUV range. ZnLa 1- x Eu x B 5 O 10 (0 ≤ x ≤ 1.0) were prepared by high temperature solid state reactions. Excitation and emission spectra prove that the concentration saturation occurs at a high Eu3+ concentration (∼60 atm%). All the phosphors emit the bright red light with a high red-to-orange ratio (2.7–3.1) and CIE coordinate (0.64, 0.36). In-situ high temperature photoluminescence spectra of ZnLa 0.4 Eu 0.6 B 5 O 10 prove its high thermal stability, i.e. the emission intensity at 150 °C remains 90% of the value at room temperature, thus being a suitable candidate for NUV-LED pumped red phosphor. ZnLa 1- x Eu x B 5 O 10 (0 ≤ x ≤ 1.0) were prepared by solid state reactions and the photoluminescence property was investigated systematically. Eu3+ locates at a 10-fold coordination environment with C 1 symmetry, thus the f - f transition at 393 nm is substantially intense and the emission quenching occurs at a high Eu3+ concentration (>60 atm%). The optimal sample ZnLa 0.4 Eu 0.6 B 5 O 10 together with commercial blue and green phosphors were combined with the 390 nm LED chip to emit a warm white light. Image 1 • ZnLa 1- x Eu x B 5 O 10 (0 ≤ x ≤ 1.0) were prepared by typical solid state reactions. • The concentration saturation occurs at a high Eu3+ concentration (∼60 atm%). • All samples emit the bright red light with a high red-to-orange ratio (2.7–3.1). • The emission intensity of ZnLa 0.4 Eu 0.6 B 5 O 10 at 150 °C remains 90%. • ZnLa 0.4 Eu 0.6 B 5 O 10 phosphor can be efficiently pumped by a 395 nm LED chip. [ABSTRACT FROM AUTHOR]

The title compounds are prepared by solid state reaction of H3BO3 (10% excess), Bi2O3, BaCO3, and Tb4O7 (staged heating, 700-850 °C, 15 h). [ABSTRACT FROM AUTHOR]

The title compounds are synthesized by solid state reactions of Ln2O3 (Ln: Sm, Eu, Gd, Dy, Ho, Er, Y) or Tb4O7, Bi2O3, and H3BO3 (650 °C for 15 h, followed by sintering at 750-820 °C for 15 h). [ABSTRACT FROM AUTHOR]