Facile synthesis of monodisperse Cu3SbSe4 nanoparticles and thermoelectric performance of Cu3SbSe4 nanoparticle-based materials

International audienceIn this study, large-scale synthesis of Cu3SbSe4 and Cu3Sb0.98Sn0.02Se4 nanoparticles with a narrow size distribution was achieved through a rapid-injection route. These nanoparticles showed a monodisperse and quasi-spherical morphology. The Cu3SbSe4 and Cu3Sb0.98Sn0.02Se4 nanoparticle-based bulk materials were then prepared by hot-pressed sinter of the nanoparticles, and their thermoelectric performances were systematically studied. Due to the reduced lattice thermal conductivity from enhanced phonon scattering at the grain interfaces of the bulk materials, the maximum ZT value of the Cu3Sb0.98Sn0.02Se4 bulk materials reached 0.50 at 575

Spectroscopic properties of Er3+ and Yb3+ co-doped glass ceramics containing SrF2 nanocrystals

International audienceThe spectroscopic properties of Er3+/Yb3+ co-doped 50SiO2-10Al2O3-20ZnF2-20SrF2 glass and glass ceramic containing SrF2 nanocrystals were investigated. The formation of SrF2 nanocrystals in the glass ceramic was confirmed by XRD. The oscillator strengths for several transitions of the Er3+ ions in the glass ceramic have been obtained and the Judd-Ofelt parameters were then determined. The XRD result and Judd-Ofelt parameters suggested that Er3+ and Yb3+ ions had efficiently enriched in the SrF2 nanocrystals in the glass ceramic. The lifetime of excited states has been used to reveal the surroundings of luminescent Er3+ and Yb3+ and energy transfer (ET) mechanism between Er3+ and Yb3+. Much stronger upconversion luminescence and longer lifetime of the Er3+/Yb3+ co-doped glass ceramic were observed in comparison with the Er3+/Yb3+ co-doped glass, which could be ascribed to more efficient ET from Yb3+ to Er3+ due to the enrichment of Yb3+ and Er3+ and the shortening of the distance between lanthanide ions in the precipitated SrF2 nanocrystals

Near-infrared emission of Yb3+ through energy transfer from ZnO to Yb3+ in glass ceramic containing ZnO nanocrystals.

International audienceYb(3+)-doped glass and glass ceramic containing ZnO nanocrystals were prepared by the melting-quenching method and subsequent heat treatment. Intense near-IR emission around 1000 nm that originated from the transition of Yb(3+):(2)F(5/2)→(2)F(7/2) was generated as a result of energy transfer from oxygen interstitials in ZnO nanocrystals to Yb(3+) with energy transfer efficiency of about 10%. The quantum yield for the near-IR emission of Yb(3+) under the excitation of 390 nm was about 16.7%. These materials have potential application in achieving high-efficiency Si solar cells via spectrum modification

Preparation and luminescence properties of Ce3+ and Tb3+ co-doped glasses and glass ceramics containing SrF2 nanocrystals

International audienceThe Ce3+ and Tb3+ co-doped glasses and glass ceramics containing SrF2 nanocrystals were prepared by melt-quenching and subsequent heat treating and their luminescence properties were described. The formation of SrF2 nanocrystals in glass ceramics was confirmed by X-ray diffraction and transmission electron microscopy. The XRD patterns and photoluminescence spectra revealed that the Ce3+ ions and Tb3+ ions have been incorporated into SrF2 nanocrystals. The decay time of excited states has been used to reveal the energy transfer mechanism between Ce3+ and Tb3+. The emission intensity of Tb3+ ions in the glass ceramics was much stronger than that in the precursor glass, which could be ascribed to the more efficient energy transfer from Ce3+ to Tb3+ in the glass ceramics due to the enrichment of Ce3+ and Tb3+ ions and the shortening of the distance between Ce3+ and Tb3+ ions in the precipitated SrF2 nanocrystals. The glasses and glass ceramics could emit bright green light by adjusting concentration ratio of Ce3+ to Tb3+ and heat treatment temperature

Spectroscopic properties of Er3+-Yb3+ co-doped glass ceramics containing BaF2 nanocrystals

International audienceA Er3+ and Yb3+ co-doped transparent oxyfluoride glass ceramic containing BaF2 nanocrystals has been prepared. The formation of BaF2 nanocrystals in the glass ceramic was confirmed by X-ray diffraction. Intense upconversion luminescence in the Er3+ and Yb3+ co-doped glass ceramic could be observed. Stark splitting of the Er3+ upconversion luminescence peaks in the glass ceramic indicated that Er3+ and Yb3+ had been incorporated into the BaF2 nanocrystals. Near infrared luminescence decay curves showed that the Er3+ and Yb3+ co-doped glass ceramic had higher luminescence efficiency than the precursor glass

Luminescence Properties of Eu2+-Doped Glass Ceramics Containing SrF2 Nanocrystals

International audienceThe Eu2+-doped glasses and glass ceramics containing SrF2 nanocrystals were prepared and their luminescence properties were investigated. The formation of SrF2 nanocrystals in glass ceramics was confirmed by X-ray diffraction and transmission electron microscopy. The melting in a reducing atmosphere and then the crystallization of glass resulted in the reduction of almost all Eu3+ ions to Eu2+ ions in the glass ceramics. The Eu2+-doped glass ceramics containing SrF2 nanocrystals exhibited a much stronger broad blue emission band and a longer lifetime of excited state than the glasses

Luminescence behavior of Er3+ doped glass ceramics containing Sr2RF7 (R=Y, Gd, La) nanocrystals

International audienceThe luminescence behaviors of Er3+ doped glass ceramics containing Sr2RF7 (R = Y,Gd,La) nanocrystals were investigated. The formation of Sr2RF7 nanocrystals in the glass ceramics was confirmed by x-ray diffraction and high resolution transmission electron microscopy. Energy dispersive x-ray spectroscopy analysis showed that the Er3+ ions were efficiently incorporated in Sr2GdF7 nanocrystals. The efficient upconversion luminescence of the Er3+ in the glass ceramics can be observed. The lifetime of the Er3+ in the glass ceramics was found to be much longer than that in the glass due to the lower phonon energy of fluoride crystals when Er3+ entered efficiently fluoride crystals in the glass ceramics

Spectroscopic properties of Er3+/Yb3+ co-doped 50SiO2-20Al2O3-30CaF2 glass and glass ceramics

International audienceA spectroscopic investigation of Er3+/Yb3+ co-doped 50SiO2-20Al2O3-30CaF2 glasses and transparent glass ceramics containing CaF2 nanocrystals is presented. The formation of CaF2 nanocrystals in the glass ceramic was confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The Judd-Ofelt parameters of the Er3+ ions in the glass and glass ceramic have been calculated; they suggested that Er3+ ions had been incorporated into CaF2 nanocrystals in the glass ceramics. The upconversion luminescence intensity of the Er3+/Yb3+ co-doped glass ceramic was much stronger than that of the Er3+/Yb3+ co-doped glass. The upconversion luminescence mechanism has been ascribed to a two-photon absorption process for the green and red luminescence and a three-photon absorption process for the blue luminescence

Nanocrystallization and photoluminescence of Ce/Dy/Eu-doped fluorosilicate glass ceramics

International audienceCe3+-Eu2+-Dy3+-Eu3+-doped fluorosilicate glass ceramics containing orthorhombic CaCeOF3 nanocrystals were prepared by annealing the precursor glass above 640 °C, along with the reduction of Eu3+ → Eu2+. Under near ultraviolet excitation, the emission bands of Eu2+ or Dy3+ were enhanced by several ten or hundred times, owing to energy transfers from Ce3+ to Eu2+ or Dy3+. The glass and glass ceramics emitted warm white light deriving from the blue, yellow and red emission from Eu2+, Dy3+ and Eu3+. Tuning the annealing temperature, the Eu2+/Eu3+ ratio and the warm white Commission Internationale de I'Eclairage (CIE) coordinates can be adjusted. Thus, the present materials can be applied on warm white high power light-emitting-diodes for indoor illumination application

Luminescence Properties of Eu2+and Mn2+Codoped 50SiO(2)-17Al(2)O(3)-23MgF(2)-10NaF Glasses and Glass-Ceramics

International audienceThe Eu2+ and Mn2+ codoped 50SiO2-17Al2O3-23MgF2-10NaF glasses and glass-ceramics were prepared and their luminescence properties were investigated. The red emission intensity of Mn2+ in the Eu2+ and Mn2+ codoped glass was about five times stronger than that in the Mn2+ doped glass, which could be attributed to energy transfer from Eu2+ to Mn2+. The energy transfer mechanism from Eu2+ to Mn2+ in glasses was determined to be a dipole-quadrupole interaction. The luminescence intensity of the glass-ceramics was stronger than that of the glass because some Eu2+ and Mn2+ ions entered lower phonon energy environment of MgF2 nanocrystals in the glass-ceramics