The Cd_{1-x}Ni_{x}Te crystals were grown by the Bridgman method. The investigated samples were cut from five different ingots with nominal contents of nickel varied from 0.005 to 0.05. The investigations were performed using X-ray powder diffraction method and energy dispersive and wavelength dispersive electron microprobe analysis. The samples were ałso examined in a scanning electron microscope. Examinations of wavelength dispersive electron microprobe analysis show that the actual contents of nickel differ from the nominal values. The solubility limit of nickel was determined to be x = 0.005. The precipitates of NiTe were found in samples of a greater content of nickel. Their dimensions were between 5 to 90 micrometers. X-ray powder diffraction measurements did not reveal any significant change of the lattice constant of investigated crystals in comparison with pure CdTe.
Based on the invention and widely application of the Czochralski pulling method, vanadate crystals have been grown and commercialized in recent decades. In this paper, the growth and characterization of a series of neodymium doped vanadate crystals have been reviewed, including Nd:YVO_4, Nd:GdVO_4, and Nd:LuVO_4. The excellent thermal-mechanical and laser property make them to be used in many respects.
The recent successful growth of single, bulk Pb_{1-x}Cd_{x}Te crystals by self-selecting vapor transport method at the Institute of Physics of the Polish Academy of Sciences in Warsaw opened new opportunities to study the physical properties of this interesting material in detail. In this work we report the preliminary results of X-ray powder diffraction studies performed on a set of Pb_{1-x}Cd_{x}Te solid solutions (where x ≤ 0.056) at high temperatures (295 K ≤ T ≤ 1100 K) and analyzed with the Rietveld refinement. Our results demonstrate the necessity of some correction of the relevant phase diagram and of the solubility limit, known from the literature.
The Czochralski method of crystal growth is used since 1950s in scientific and industrial laboratories for growth of single crystals of large size and high quality. The article presents the general characteristics and selected improvements of the Czochralski method, and discusses its meaning and advantages in growth of silicon single crystals playing a key role in microelectronics.
The growth of series of actual laser crystals belonging to different structural types by the Czochralski method is presented. The primary attention is given to single crystalline compounds and their solid solutions with garnet structure (scandium-containing rare-earth garnets with general formula {LnSc}_3[ScMe]_2Me_3O_{12}, Me = Al, Ga) as well as with olivine (forsterite Mg_2SiO_4) and scheelite structure (double tungstates and molybdates with formula NaLn(TO_4)_2, where T = Mo or W). The broad bands of luminescence and absorption produced by activator ions in these laser hosts that appear either as a result of structural disorder (garnets, scheelites) or due to the doping by transition metal ions (chromium in forsterite) join together these representatives of different structural classes and determine their application in photonics. The paper considers the problems of growing of large crystals with uniform distribution of components and dopants, determination of congruently melting composition, especially in compounds with complex isomorphism. The mutual influence of components and dopants, redistribution of ions along crystallographically non-equivalent sites in the structure, alteration of valency of transition metal ions accompanied with the change of their segregation coefficients under variation of redox conditions is discussed.
Electron probe microanalysis and X-ray diffraction studies have been performed on samples of ternary Cd_{1-x}Mg_{x}Te (0.05 ≤ x ≤ 0.09) and quaternary Cd_{1-x-y}Mg_{x}Mn_{y}Te (0.025 ≤ x ≤ 0.4; 0.025 ≤ y ≤ 0.7) alloys. The investigated samples were cut from 24 different ingots grown by Bridgman method. Microprobe examinations have revealed significant differences between actual and nominal content of Mg along the longitudinal direction for both ternary and quaternary ingots. In contrast to Mg, for most Cd_{1-x-y}Mg_{x}Mn_{y}Te samples the actual Mn content was within ±5% of nominal content. The lattice constants have been determined by X-ray powder diffraction method. Whereas Cd_{1-x-y}Mg_{x}Mn_{y}Te samples exhibit only zinc blende crystal structure for the entire region of x and y investigated, the Cd_{1-x}Mg_{x}Te alloy has two different structures depending on Mg content; a zinc blende structure below x = 0.5 and a wurtzite structure above it. In both alloys the lattice constant decreases with increasing Mg content.
Oxide crystal scintillators play a considerable role in fundamental and applied researches. However, working out of new generation of high-sensitivity equipment and new methods of research puts higher requirements. The ZnBO_{4} (B = W, Mo) crystals were grown from charge in platinum crucibles with high frequency heating, using the Czochralski method. The raw powder with optimum composition was prepared by solid phase high temperature synthesis using ZnO and BO_{3} (B = W, Mo) with 4-5N purity. Single crystals with sizes up to ∅ 50 × 100 mm were grown and scintillation elements of various sizes and shapes (cylinders, rectangular and hexahedron prisms) were produced. High spectrometric characteristics were obtained for ZnWO_{4}:R = 8-10% under excitation by ^{137}Cs (E_{γ}=662 keV), low radiation background (less than 0.2 mBq/kg) and low afterglow (0.002%, 20 ms after excitation). The obtained results demonstrate good prospects for ZnWO_{4} and ZnMoO_{4} crystal scintillators for application in low-count rate experiments, searching for double beta decay processes, interaction with dark matter particles, and also studies of rare decay processes. The material has also a good potential for application in modern tomography, scintillation bolometers and for other major researches using scintillators.
This study focuses mainly on the verification of a peritectic reaction during the crystallization of quasicrystals. The β and λ phases apparently provide the necessary material for crystallization of the quasicrystalline ψ phase. We present results of an experimental visualization of the evolution of the flux dissolution process of the high temperature β phase. Solidified droplets of the β phase, formed primarily by the surface tension of the liquid within a bubble or a shrinkage, after crumbling during the flux dissolution may contribute to the quasicrystal formation process according to a peritectic reaction: β_{c} + λ + L → ψ, where β_{c} denotes the crumbled β phase immersed in the liquid.
Single crystals of SrPrGaO_{4} and SrLaGaO_{4} have been grown using the Czochralski technique. Both materials melt incongruently at 1462°C and 1516°C. The non-stoichiometric crystals contain more strontium than the starting melts. Constitutional supercooling is retarded by special growth conditions and optimum melt composition. Because of their small mismatch both crystals are recommended as substrates for YBa_{2}Cu_{3}O_{7-x} epitaxy.
The paper reports on the growth conditions of Li_2B_4O_7 single crystals in both pure and Yb, Co, Mn doped systems. The crystals were grown by the Czochralski method using an intentional concentration of the above-mentioned ions at a level of 0.5 mol.%. The pure and Mn-doped crystals were found to be highly transparent and clear. The crystals doped with Yb_2O_3 had a lot of precipitations making them opaque. The Co-doped crystals were purple-blue in colour and highly transparent. The growth of Yb and Co doped Li_2B_4O_7 crystals was reported for the first time in this paper. Absorption was measured in the range of 200 to 3200 nm, moreover analysis of changes in the absorption spectrum ofγ-irradiated pure and doped Li_2B_4O_7 crystals was performed. Some thermoluminescence properties were measured, e.g. energies and lifetimes of the traps of different charge carriers occurring in the crystals at low temperatures.
Czochralski method of crystallization allows obtaining single crystals of many intermetallic compounds. New series Gd_7Ni_xPd_{3-x} (x=2, 3) intermetallics was grown by the modified Czochralski method using a levitated melt in protective argon atmosphere. Preliminary studies of magnetic properties have shown that all crystals of the series order ferromagnetically. It was found that Gd_7Ni_2Pd shows magnetic transition to the ferromagnetic state at 225 K while Gd_7Ni_3 orders at 145 K.
Uranium(3+) doped single crystals of Cs_{2}LiYCl_{6} with a 0.3 and 2.0% U^{3+} concentration have been obtained by the Bridgman-Stockbarger method. Luminescence spectra of the crystals were recorded at 27 and 15 K, respectively. The emission bands observed in the visible and near infrared regions have been assigned to transitions from the ^{4}I_{11/2}, ^{4}F_{3/2}, and ^{4}G_{7/2} levels to the ^{4}I_{9/2} ground level.
Uranium(3+) doped single crystals of RbY_{2}Cl_{7} with a uranium concentration of 0.05% and 0.2% were grown by the Bridgman-Stockbarger method using RbU_{2}Cl_{7} as the doping substance. Polished plates of ca. 5 mm in diameter were used for measurements of luminescence and excitation spectra. Since the U^{3+} ions occupy two somewhat different site symmetries, a splitting of all observed f-f bands was observed. The analysis of the spectra enabled definitively an assignment of 22 crystal field bands for both site symmetries as well as the total crystal field splitting of the ground level, equal to 473 cm^{-1} and 567 cm^{-1} for the first and second site symmetry, respectively.
We present results of investigation on growth of solid solution crystals with perovskites and K_2NiF_4 structures used as substrates for epitaxy. Perovskite single crystals with no twins and crystals with K_2NiF_4 structure with the lattice parameter in the range 3.876-3.819Å and 3.754 to 3.688Å, respectively, can be grown. Here preliminary results on investigation on growth of other solid solution crystals with the lattice constant from 3.946 to 3.688Å are also presented thus covering the whole interesting range for depositing oxide materials. These crystals can be grown by the Czochralski method that secures their high structural quality. Discussed crystals are resistant to reaction with the deposited oxide layers.
The pseudo-cubic lattice parameters of rare-earth (RE) scandate, REScO_3, single crystals grown by the Czochralski technique with RE = Dy to Pr lie between about 3.95 and 4.02 Å. These crystals are the only available perovskite substrates in this lattice constant range that can withstand virtually any thin film growth conditions. Two members of this series, PmScO_3 and EuScO_3, are, however, not suitable for substrate applications. Because the pseudo-cubic lattice parameters between neighbouring REScO_3 compounds decrease with rising atomic number of the RE in about 0.01 Å steps, the unsuitability of PmScO_3 (radioactivity) and EuScO_3 (incompatibility with Si) causes an interruption in this lattice spacing sequence. To replace them, solid solutions of their adjacent rare-earth scandates, i.e., (Nd_{0.5}Sm_{0.5})ScO_3 and (Sm_{0.5}Gd_{0.5})ScO_3, were grown by the Czochralski method. Their average pseudo-cubic lattice parameters of 3.9979 Å and 3.9784 Å are very close to those of PmScO_3 and EuScO_3, respectively, and they show very low segregation. These qualities make these solid solutions excellent substitutes for PmScO_3 and EuScO_3.
The present paper briefly overviews the application of the Czochralski method for growth of a set of oxide crystals for photonics, as well as the design of equipment at the Institute for Single Crystals, NAS of Ukraine. The examples of crystal growth and their characterization are described. The simultaneous Q-switched lasing and self-Raman frequency conversion were demonstrated in Nd-doped PbWO_4 and PbMoO_4 crystals grown by the Czochralski method. The slope lasing efficiency obtained for a PbMoO_4:Nd^{3+} laser is the best result for all the crystals with the scheelite-type structure. A detection unit with high scintillation characteristics based on a large volume (V ≈ 350 cm^3) CdWO_4 crystal was produced. Crystal growth procedures and properties of new double tungstate and vanadate crystals are presented, too.
In this article there are presented the developments on the crystal growth by the Czochralski method of fluoride laser materials at the Center for Lasers and Applications from Institute of Nuclear and Energy Research, IPEN, Brazil. A brief report of the Czochralski furnace preparation for fluorides growth regarding to its construction materials, influence of the heating assemblies in the thermal profiles and the benefits of using a suitable atmosphere is provided. Moreover, to demonstrate the importance of this technique to the advances on laser systems over the last years there are described the specific growth conditions established to obtain fluoride crystals with suitable properties for practical application as laser hosts. LiREF_4 (RE = rare earth) scheelite crystals have been studied to compare LiYF_4 (YLF) with its isomorphs, including solid solutions of the type-LiY_{1-x}Ln_{x}F_4 (Ln = Gd or Lu) and LiGd_{1-x}Lu_{x}F_4, relating to their optical quality, spectroscopic and laser properties. Some results regarding the development of new laser hosts of these materials doped with Nd, Er, Pr and co-doped Yb, Nd and Tm are also presented. The growth particularities of transition metals doped fluoride crystals such as BaLiF_3:TM (TM = Ni and Co) and LiSrAlF_6:Cr are also reported.
The Czochralski method is one of the very few melt growth techniques that are industry friendly when considering the combination of quality, dimensions, and cost of the produced crystals suitable for their commercialization in scintillation detectors. This method is one of the oldest and most developed crystal growth processes regarding an adequate understanding the physical phenomena observed during solidification process and its practical expansion especially in the industrial scale production. It allows controllable formation of single-crystalline cylindrical ingots of various inorganic scintillation materials. The review summarizes recent progress on the Czochralski growth of a number of scintillation materials. The oxide crystals are mainly considered including the Ce and Pr-doped RE_3Al_5O_{12}, RE = Y, Lu, aluminum garnets and newly discovered ultraefficient Ce-doped Gd_3(Ga,Al)_5O_{12} multicomponent garnet, high density PbWO_4 and CdWO_4 tungstates, Ce-doped RE_2SiO_5, RE = Y, Gd, Lu, oxyorthosilicates and (Y,Lu)AlO_3 aluminum perovskites and finally the classical Bi_4Ge_3O_{12} scintillator. Additionally, the details of the growth of other practically important non-oxide crystals, namely the Ce and Eu-doped LiCaAlF_6 neutron and ultraefficient Ce-doped LaBr_3 scintillators, are discussed. The potential of novel micro-pulling down growth method is briefly described in the combinatorial search for new scintillator materials. Selected luminescence and scintillation characteristics including the spectra and decay kinetics, light yield and radiation resistance are also illustrated and overviewed.
New results on ternary InGaAs crystals grown using liquid encapsulated Czochralski technique with constant liquid composition are reported. X-ray high-resolution diffractometry (rocking curves and reciprocal space maps) as well as X-ray topography using the transmission Lang setup were used. Growth history of the bulk ingots was revealed.
On the occasion of the centennial of the invention of the Czochralski crystal growth process by the Polish scientist Jan Czochralski, a review of selected strategies for the automatic control of this process is given. This review provides a sketch of the fundamental challenges of controlling the Czochralski process and the basic concepts of feedback control. Both early and modern approaches to the control of the Czochralski process are described. The discussion focuses on questions related to feed-forward control, feedback control, and state estimation. The presented methods rely on simple mathematical process models in contrast to the finite element model-based approaches typically used in crystal growth process design and analysis. Such mathematical models motivate both the structure and parameters of the chosen controller. A comprehensive list of references to background literature on this topic completes this survey.
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