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Abstract: A series of xCe3+/yDy3+: Sr3Y2−x−y (BO3)4 (x =0–0.8, y =0–0.5) phosphors have been successfully synthesized by a solid-state reaction route. Microstructure, emission spectra, decay curves and energy transfer process in the samples were investigated and discussed. With increasing of Ce3+ content (x) from 0.005 to 0.80, the variation of Ce3+ content at the two different Y3+ sites induces red-shifting of emission band from 410 to 457nm in the Ce3+ single-doped sample. Efficient energy transfer from Ce3+ to Dy3+ occurs owing to the spectral overlap between Ce3+ emission and Dy3+ excitation, which results in a great enhancement of Dy3+ emission. The energy transfer process is proposed to be dominated by the electric dipole–quadrupole interaction, and the critical distance is determined to be 1.60nm. [Copyright &y& Elsevier]

Abstract: Ultraviolet multiphoton upconversion emissions of Eu3+ (5 H 3–7, 5 G 2–6, 5 L 6 → 7 F 0) and Gd3+ (6 I J , 6 P J → 8 S 7/2) are studied in the Eu3+ (or Gd3+) doped SiO2–Al2O3–NaF–YF3 precursor glasses and glass ceramics containing β-YF3 nanocrystals, under continuous-wavelength 976nm laser pumping. It is experimentally demonstrated that energy transfer from Yb3+ to Tm3+, then further to Eu3+ or Gd3+ is responsible for the upconversion process. Compared to those in the precursor glasses, the upconversion emission intensities in the glass ceramics are greatly enhanced, owing to the participation of rare earth ions into the low-phonon-energy environment of β-YF3 nanocrystals. Hopefully, the studied glass ceramics may find potential applications in the field of ultraviolet solid-state lasers. [Copyright &y& Elsevier]

Abstract: Transparent SiO2–Al2O3–BaCO3–YF3–BaF2 glass ceramics co-doped with Yb3+/Ho3+ ions were prepared by melt quenching and subsequent heating. X-ray diffraction and transmission electron microscopy observation revealed that BaYF5 nanocrystals incorporated with Yb3+ and Ho3+ were precipitated homogeneously among the oxide glass matrix. Three upconversion emission bands centered at 483nm, 545nm and 645nm, corresponding to the 5 F 3 → 5 I 8, 5 S 2, 5 F 4 → 5 I 8 and 5 F 5 → 5 I 8 transitions of Ho3+ respectively, were detected under 976nm excitation, ascribing to the efficient energy transfer from Yb3+ to Ho3+. The red emission is prevailing in the precursor glass, while the green one turns to be dominant in the glass ceramic. [Copyright &y& Elsevier]

Abstract: The olive-like YF3 micro-particles were fabricated via a two-step route. The precursor NH4Y3F10 nano-cages sized 8nm with hollow interiors were first synthesized in a solid reaction at room temperature. In the course of subsequent hydrothermal treating, the unstable NH4Y3F10 nano-cages were decomposed, resulted in the formation of Y(OH)1.63F1.37 micro-tubes. Prolonging the hydrothermal reaction induced the further decomposition of Y(OH)1.63F1.37 to produce YF3 nano-crystals, which then aggregated together forming the final olive-like YF3 micro-particles. For the Er3+/Yb3+ co-doped olive-like YF3 micro-particles, intense visible upconversion emissions were measured under 976nm excitation owing to the partition of rare earth ions in the lattice, indicating this material a promising luminescent host. [Copyright &y& Elsevier]

Highlights: [•] A novel transparent glass ceramic containing Cs3LaCl6 nanocrystals was fabricated. [•] Crystallization behaviors of Cs3LaCl6 nanophase are systematically investigated. [•] The up-/down-conversion emissions are greatly intensified after crystallization. [ABSTRACT FROM AUTHOR]

Abstract: Tm3+-sensitized up-conversion and down-conversion are studied in transparent glass ceramics embedded with β-YF3 nanocrystals. Upon excitation at 1220nm, where crystalline silicon (c-Si) solar cells no longer absorb, the sub-bandgap photons could be converted to the higher-energy ones via up-conversion. In addition, under excitation at 468nm (a wavelength close to the peak in the air-mass 1.5 global solar spectrum), one blue photon might be split in up to two near-infrared ones via down-conversion. In both cases, the frequency-converted photons match the spectral response of c-Si solar cell well. Hopefully, the investigated luminescent materials may act as the spectral conversion layers to reduce the sub-bandgap transmission and charge carrier thermalization losses of c-Si solar cells, and in turn, enhance the energy efficiency. [Copyright &y& Elsevier]

Abstract: Nd3+-doped GeS2–In2S3–CsCl transparent chalcohalide glass ceramics containing In2.67S4 nanocrystals are prepared by melt-quenching and subsequent heating. The influence of Nd3+ doping on the In2.67S4 crystallization, the microstructure, as well as the transmission and photoluminescence spectra of glass ceramics are investigated. It is proposed that Nd3+ ions act as nucleating agents for In2.67S4 crystallization in the sample with relative low Nd3+ concentration, while a part of Nd3+ ions are believed being expelled from the crystallized regions and aggregate on the surfaces of the crystallites during crystallization when Nd3+ concentration is increased, which suppresses crystal growth, resulting in nano size and homogeneous distribution of grains, and subsequently remarkable blue-shift of the optical absorption edge of the glass ceramic. Evidently, the microhardness of chalcohalide glass is strengthened after the precipitation of In2.67S4 nanophase. [Copyright &y& Elsevier]

Abstract: Transparent oxyfluoride glass ceramics with composition of 45SiO2–25Al2O3–5CaCO3–10NaF–15CaF2–0.5ErF3 (in mol%) were developed through controlled crystallization of melt-quenched glass. Non-isothermal crystallization kinetics investigation showed that the average apparent activation energy E a and Avrami exponent n are about 283kJ/mol and 2.22, respectively, indicating the crystallization a three dimensional crystal growth process controlled by the diffusion with a decreasing nucleation rate. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observation revealed the precipitation of CaF2 crystallites sized about 15nm among the glass matrix after heat-treatment at 650°C for 2h. For as-made glass, no upconversion signals were detected when excited with a 30mW diode laser at 980nm, while strong upconversion emissions at 545, 660 and 800nm were obtained for transparent glass ceramic under similar excitation condition. [Copyright &y& Elsevier]