Czochralski growth of Yb doped oxyapatite for high power laser application

Ca₈(La,Yb)₂(PO₄)₆O₂ (Yb:CLPA) single crystals with the apatite-type structure could be grown from the melt using the Czochralski method. Grown crystal was 18 mm in diameter and 110 mm in length. It is transparent with slightly blue color. Neither visible inclusion nor crack was observed. Thermal conductivity of Yb:CLPA was calculated from the values of thermal diffusivity, heat capacity measurement and density. Luminescent characterization was carried out from the results of emission, absorption and Raman spectrum.     

Quartz Ore Beneficiation by Reverse Flotation for Silicon Production

Silicon - In this work the reverse flotation as beneficiation process for high-purity silica valorization from Draissa quartz deposits (Algeria) is studied as a potential raw material for...     

Fiber Single-Crystal Growth from the Melt for Optical Applications

The micro-pulling-down technique has been applied to produce undoped and 0.1% Nd³⁺-doped Y₃Al₅O₁₂ garnet single-crystal fibers with controlled diameter. The hot zone construction and fiber-pulling conditions have been optimized. As a result, growth of transparent and homogeneous fiber crystals has been achieved. The crystals have been grown under 10⁵ Pa (1 atm) of argon atmosphere, with the pulling rate varied in the range of 0.3–2.0 mm/min. One hundred percent of the starting melt has been normally transformed into a crystalline material, with an empty crucible ready for the next growth procedure. The as-produced fibers demonstrate promising optical properties.     

Orientations and seed type effect on Al2O3-YAG-ZrO2 eutectic microstructure solidified from the melt by the micro-pulling down technique

Al₂O₃-YAG-ZrO₂ eutectic ceramic rods of 5 mm in diameter were grown by micro-pulling down technique. The seeding and the solidification rate affect microstructure, morphology, crystallography, and thermal stress of the solidified ceramics. The ternary eutectic grown through zirconia (111) seed had inhomogeneous and irregular cellular microstructures. At the stationary stable regime, the microstructure spacing (λ) depends on the pulling rate (v). Under solidification rate of 0.5 mm.min^?1, the rods grown by using eutectic poly-crystal, (100), (111) YAG, and c(0001), A(1?210), M(10?10) sapphire seeds, the YAG and ZrO₂ phases are oriented along the <100> direction parallel to the growth direction. The zirconia (111) seeding X-ray diagram eutectic presents additional peaks and the monoclinic ZrO₂ phase appears at the solidification rate of 1 mm.min-1. The rods grown through ZrO₂ seeding are more stressed than those solidified by using eutectic, YAG and sapphire seeds, respectively.     

Compositional and Temperature Effects on Stability and Superconducting Behaviour of 1223 Type Phases

The studies have been focused to the determination of the best elaboration conditions of Tl-1223 phases. The objectives were to obtain a well defined composition and an optimization of the superconducting behaviour by Tl/Pb, Sr/Ba and O/F substitutions. To reach these objectives, we have investigated the monophased field of Tl/Pb, Sr/Ba-1223 phase in dependence on composition and temperature and the compositional effect on the superconducting behaviour. Samples were elaborated by conventional solid state reaction in flowing oxygen from a stepwise process.     

Effect of Ba Substitution on the Superconducting Properties and the Irreversibility Line of the Compounds TIPb 1223: Tl0.5Pb0.5(Sr 2−xBax)Ca2Cu3O9−δ

The superconducting properties and the irreversibility line of the Tl_0.5Pb_0.5(Sr_2?xBa_x)Ca₂Cu₃O_9?δ were studied by ac susceptibility on both ceramic and powdered samples. The samples were prepared by solid state reaction in flowing oxygen at 880°C or in sealed quartz tube at 960°C. The irreversibility lines were measured up to 4 Tesla and were determined by the maximum of the X″ peak, using the same ac field to allow comparison between them. The presence of the 1212 phase as a minor superconducting phase was clearly evidenced in all cases. The case of samples of TlPbl223 with Tl/Pb ratio different from unity was also examined.     

Improvement of the Irreversibility Line of the 1212 Compound Tl0.5Pb0.5Sr2CaCu2O7−δ

The superconducting properties and the irreversibility line of the Tl_0.5Pb_0.5Sr₂CaCu₂O_7?δ were studied by ac susceptibility on both ceramic and powder samples prepared in sealed quartz tube at 960°C. In parallel, carefull investigations by DTA/Tg, X rays diffraction and plasma emission spectroscopy were performed on each sample after each thermal treatment. It is shown that the superconducting properties are strongly dependent on further heat treatments and that the irreversibility line may be optimized. Nevertheless, the results obtained suggest that further improvement of the irreversibility line might be expected.     

Monophase domain, fibers single crystals grown by the micro-pulling down technique and optical characterisation of LiGd1−xYbx(WO4)2

We have determined the single phase domain of LiGd_1−xYb_x(WO₄)₂. The lattices parameters decrease as a function of Yb³⁺ substitution in Gd³⁺ sites. Transparent LiGd_1−xYb_x(WO₄)₂ fibers single crystals were successfully grown by the micro-pulling down technique (μ-PD). The Yb³⁺-doped LiGd(WO₄)₂ fibers single crystals have been pulled under stationary stable growth conditions corresponding to flat crystallization interface with meniscus length equal to 120 μm. The fibers diameters varied from 0.5 to 1 mm depending on the capillary die diameter, pulling rate and the molten zone temperature. Fibers single crystals free of defects are observed for Ytterbium concentration in the melt up to 5 at%. Above this limit, inclusions and cracks appear and the optical quality of the fibers were deteriorated. The emission spectra of Yb³⁺-doped LiGd(WO₄)₂ were investigated.     

Evaluation of Fiber-Shaped LYSO for Double Readout Gamma Photon Detection

Recently, the development of the micro pulling-down method has allowed the growth of single inorganic scintillation crystals with a uniform fiber shape. The dimensions may vary from 0.3 to 3 millimeters in diameter with length up to 1 meter. This paper presents an experimental set up built in order to study the scintillation light propagation within fiber shaped crystals. The interaction position of a gamma photon in the fiber is determined by a coincidence method. Light yields measured by photomultipliers at both sides of the fiber are correlated to the photon interaction position and the scintillating properties of the crystals. X-ray excited luminescence experiments were also performed to study the process of light attenuation along the fibers. X-ray and gamma ray measurements are in good agreement. Two cerium doped lutetium yttrium orthosilicate Lu_2(1-x)Y_2x SiO₅:Ce³⁺ fibers have been studied. The first was a cylindrical crystal fiber of 6.9 cm in length and of 1 mm in diameter obtained by the micro pulling-down technique. The second was a squared shaped fiber crystal of 1times1times43 mm³ obtained from a bulk after cutting and polishing. The interaction localization can be determined with a precision from 4 to 12 mm depending on the fiber shape     

Recent progress on elaboration of undoped and doped Y2O3, Gd2O3 rare-earth nano-oxide

Some selected materials with small sizes in the nanometer region are reviewed. Different methods for synthesis of nanoscale materials are classified and discussed. Basic prerequisites for successful use of the materials for nanotechnology application are their synthesis with specific and homogeneous composition and geometry. This review summarizes recent results on nanoscale materials containing optically active lanthanide ion especially focused on Y2O3 and Gd2O3 oxide.