Papers by Keyword: Crystal Growth

Abstract: The Cd_1-xMn_xTe crystal is believed to be a good candidate to compete with Cd_1-xMn_xTe in the X-ray and γ-ray detector application. In this paper, Indium (In) doped Cd_0.8Mn_0.2Te (CdMnTe) ingots were grown by the modified Vertical Bridgman method. The as-grown crystals were characterized using Near-Infrared (NIR) transmission spectrum mapping of composition, X-ray double-crystal rocking curve measurement, I-V measurement and ²⁴¹Am gamma rays radiation measurement. The Mn composition extracted from the NIR spectra at different axial and radial distances of the 30×40×2 mm³ CdMnTe wafers shown that the Mn concentration in the range of 0.19430.0008 to 0.2020.0025 mole fraction. The FWHM values of the X-ray rocking curves are of 40-80 arc sec, indicating a high crystalline perfection. The resistivity of the wafers is (2-3) ×10¹⁰Ω.cm. The CdMnTe planar detector irradiated by ²⁴¹Am source shows the energy resolution of 8.5%.

Abstract: Cubic KTa_1-xNb_xO₃ single crystals with difference compositions have been grown by Czochralski technique in KTaO₃- KNbO₃ solid solution system. Growth habit, morphological feature, and other properties of two different composition KTN crystals, KTa_0.65Nb_0.35O₃, and KTa_0.63Nb_0.37O₃ are investigated in this work. The X-ray diffraction (XRD) experimental results show that all crystals belong to cubic phase at room temperature, lattice parameter a is 3.993 and 3.994Å corresponded to the composition of x (Nb) =0.35, 0.37, respectively. HXRD and AFM measurement results show all KTN crystals are in high integrity and good quality. The transmittance spectra of KTN crystals show that the cut off wavelength of KTN crystals decreased with the Nb increasing in the crystal. The dielectric-temperature measurement results shows KTN crystal have optimal performance on Kerr effect at the Currie temperature of the crystal. All the results show that the KTN crystals we grown are in good quality and have a broad application prospects

Abstract: Triclinic and hexagonal structure of TbBO₃ was synthesized by Sol-Gel combustion method and high temperature solid state method respectively. The TbBO₃ crystal was grown by fluxing Czochralski(CZ) method and LiBO₂ as flux. The crystal structure was studied by FT-IR and DTA. The results of powder magnetic susceptibility of hexagonal one showed that TbBO₃ may be a good candidate magneto optical material.

Abstract: The influences of saline waterproof agent composed of carboxylic acid sodium (RCOONa), Al₂(SO₄)₃, K₂SO₄ on the hydration of semi-hydrated gypsum were investigated. The results showed: (1) with the concentration of K₂SO₄ increasing, the ζ potential rose due to the increasing K⁺ entering the electric double layer of gypsum; (2) with the concentration of Al₂(SO₄)₃ heightening, the ζ potential gradually decreased as a result of the formed AFt phase during the hydration process and the increasing Al³⁺ entering the electric double layer of gypsum. The ζ potential rose because the RCOO^- base groups adhered to the surface of gypsum crystal, which slowed down the growth rate of the gypsum crystal in direction c, and short hexahedron poles were produced.

Abstract: Under the condition that the solid-liquid interface bends periodically in continuous casting, the expression of solid-phase growth rate adapting to continuous casting was set up, and then the growth rates were calculated. On this basis, the morphologic of crystal growth and the variation of primary dendrite spacing during continuous casting slabs were studied. The results show that the growth rate is the fastest when solid-phase moves to wave crest within a deformation periodicity, whereas the growth rate is the slowest when the crystal moves to wave hollow. The bigger the bulge size is, the greater the variation amplitude of the growth rate will become. The variation of the growth rate results in the S/L interface to develop towards a planar surface. Because the value is much smaller than the critical value of the transformation from cells to dendrites, and the crystals only grow in the fashion of dendrites. The primary dendrite spacing at wave crest is bigger than the primary dendrite spacing at wave hollow in early stage of columnar crystal growth, and the dendrite spacing at wave crest is basically equal with the dendrite spacing at wave hollow in the late stage of solidification, and they quickly simultaneous increase. Good correlation is obtained between the experimental results and the calculation results of the dendrite arm spacing.

Abstract: In this paper, we reported a facile microwave-assisted green chemical route to prepare pure, uniform, and monodispersed Cu₂O octahedron wrapped by the {111} faces by using glucose as a reducing agent. X-ray diffraction (XRD), energy dispersive X-ray spectrometry(EDX) and field emission scanning electron microscopy (FESEM) were used to characterize the as-synthesized products. It was found that the morphology and structure of Cu₂O crystals were greatly affected by the concentration of NaOH. A solid-solution-solid growth mechanism was possibly proposed on the basis of the comparative experimental results.

Abstract: A reduced-pressure melts growth method was first presented to grow the vacuum ultraviolet double frequency crystal KBe₂BO₃F₂ (KBBF). The bulk KBBF crystal, with a dimension of about 11mm×10mm×5mm, has been grown successfully, and the grown crystal exhibits a high optical homogeneity except for the seed zone. The optical transmittance spectrum of the grown KBBF crystal was measured and it indicated that the high-frequency absorption edge is observed at 160nm, the transmittance is up to about 70% between 250nm and 400nm. The results show that the reduced-pressure melts growth is a promising growth method for bulk KBBF crystal and the grown KBBF crystal is possible for applying as a frequency-doubling device for the vacuum ultraviolet region.

Abstract: We have successfully synthesized single-crystal samples of fast Li-ion conducting cubic Li₇La₃Zr₂O₁₂ with the garnet related-type structure by a self-flux method using LiNO₃ at 1150°C. The as-grown Li₇La₃Zr₂O₁₂ crystals are colorless and transparent; they also have a polyhedral-shape with a maximum dimension of 0.15 ´ 0.10 ´ 0.10 mm³. The powder XRD pattern shows the obtained crystals have cubic Li₇La₃Zr₂O₁₂ structure, and the EDX analysis confirms the chemical composition of La : Zr = 3 : 2.

Abstract: High-performance single crystals of ferroelectric Bi₄Ti₃O₁₂ (BiT) have been successfully obtained via the top-seeded solution growth under high oxygen pressure (Po₂) atmosphere. Crystals grown at 960°C at a Po₂ of 0.9 MPa exhibited a well-saturated hysteresis loop with a remanent polarization of 48 mC/cm² and a coercive field of 29 kV/cm. The results of piezoresponse force microscopy indicate that polarization switching is accomplished throughout the BiT crystals obtained. Electric-field-induced strain measurements along the a axis yield a piezoelectric constant d₁₁* of 37 pm/V for BiT.

Abstract: Spontaneous self-assembling of interacting atoms prototyping crystallization and reconstructive phase transitions in crystalline state is discussed in terms of Atomic Density Function (ADF) theory. It is demonstrated that a multi-mode potential can reproduce any crystal structure. 3D computer modeling of formation of the FCC crystal and crystal lattice rearrangement in the FCCàBCC transformation is presented.