Crucible Method Research Articles

Growth of Semi-Insulating GaAs Crystal with Uniform Si Doping

An improved double crucible method of melt replenishing to counteract the dopant segregation effect in order to grow homogeneous doped GaAs crystals is brought forward, and its validity and feasibility are demonstrated by analytical and numerical study. The numerical results show that the new method can suppress the increase of dopant concentration near the growth interface and can maintain the homogeneity of dopant distribution along the radial direction. The positions of replenishing melt exit almost have no effects on the axial and radial distribution homogeneity of dopant Si in the crystal. So the new method has many distinct advantages: it can improve the crystallization rate and size, the operation is flexible, etc.

High-speed growth of Si single bulk crystals by expanding low-temperature region in Si melt using noncontact crucible method

We propose a high-speed growth based on noncontact crucible method for obtaining large ingots with a constant diameter. In this method, the Si melt used has a large low-temperature region in its central upper part to ensure Si crystal growth inside it. Therefore, this method has the possibility of attaining a high growth rate using a high cooling rate because the growth rate is determined by the rate of expansion of the low-temperature region in the Si melt. The horizontal and vertical growth rates in Si melts were experimentally determined. At a cooling rate of 0.4K/min, the horizontal growth rate reached 1.5mm/min in the <110> direction and 1.9mm/min in the <100> direction. These growth rates are higher than that of the cast method. The growth rate increased with the cooling rate. The vertical growth rate was determined to be 0.3–0.6mm/min, and it tended to increase with increasing depth of the Si melt. The diameter of an ingot remained constant during pulling due to a high cooling rate of 0.4K/min because the horizontal growth rate increased as the cooling rate increased and the melt temperature markedly decreased. An ingot with a constant diameter of 21cm and a height of 7cm was obtained inside a Si melt by the high speed growth using a crucible with 33cm diameter.

Downscaled method using glass microfiber filters for the determination of Klason lignin and structural carbohydrates

The analysis results of Klason lignin and structural carbohydrates determined by downscaled analysis methods using 50 mg and 5 mg biomass and glass microfiber filters for the filtration of acid-insoluble lignin, were compared to a conventional method using 300 mg biomass and ceramic crucibles. The usage of microfiber filters reduces space requirement in oven and furnace to a minimum and speeds up the filtration of Klason lignin about three-fold. Furthermore, tedious cleaning of crucibles is unnecessary which additionally increases the number of samples that can be analyzed in a given time frame. The analysis of 5 feedstocks comprising herbaceous, hard- and softwood, revealed no significant differences of hemicellulosic sugars between the 50 mg microfiber and the 300 mg crucible method. The 50 mg microfiber method resulted in Klason lignin values in the range of −6.1% to +4.0% (relative) and glucan values in the range of −0.8% to +3.7% (relative) of the values obtained with the 300 mg crucible method. The 50 mg microfiber method was highly reproducible with relative standard deviations (RSD%) of 0.27–0.56% (average 0.38%) for Klason lignin and 0.54%–1.46% (average 1.01%) for glucan. Compared to the 50 mg microfiber method, the 5 mg microfiber method resulted in similar deviations of Klason lignin and glucan from the 300 mg method values. However, the reproducibility was slightly lower. Overall, the 50 mg and 5 mg microfiber method reflected the actual biomass composition with sufficient accuracy and are therefore recommended as alternative methods or when downscaling of the analysis is required.

Synthesis of SnO2@SnS2 core–shell nanorods by double crucible method and their photocatalysis

SnO2@SnS2 core–shell structural nanorods were prepared by the solid phase double crucible method. The structure, morphology and optical properties of the as-prepared samples were characterized by X-ray diffraction, transmission electron microscope and ultraviolet–visible–near-infrared spectrophotometer. The results indicated that the mixture of hexagonal phases SnS2 and tetragonal phase SnO2 was formed at 400 and 500 °C and the molar ratio of SnO2 to thioacetamide was 1:3. SnS2 was uniformly coated on the surface of SnO2 nanorods, and SnO2@SnS2 core–shell nanorods with the shell thickness of about 3–5 nm were obtained. Furthermore, their photocatalytic properties were tested for the degrading of methyl orange in water under visible light (λ > 420 nm) irradiation. Compared with pure SnS2 nanomaterials, the core–shell nanorods demonstrated more superior photocatalytic activity. These meaningful results had laid certain foundation for further research on metal oxide@metal sulfide core–shell structure nanomaterials.

Growth of large diameter ZnTe single crystals by the double crucible liquid encapsulated pulling method

AbstractIn our work, large diameter ZnTe single crystals were grown by various melt growth methods. By a liquid encapsulated vertical gradient freezing method, crystals with large grains and low dislocation density were obtained. By a liquid encapsulated Kyropoulos method, 80 mm diameter crystals were successfully grown from ZnTe seed crystals. However, crystals grown by the both methods had large strain and cracks owing to difference in coefficient of thermal expansion between an encapsulant and ZnTe. Therefore, a new crystal growth method was developed. Two crucibles were used in the new method. It was named double crucible liquid encapsulated pulling method. Crystals up to 100 mm in diameter and 40 mm in length were reproducibly obtained. Both &lt;100&gt; and &lt;110&gt; crystals were successfully grown. The etch pit density of the grown crystal was lower than 10,000 cm–2 and any large strain or cracks were not observed. In order to reduce Te inclusions, wafer annealing was examined. Most Te inclusions were eliminated with suitable Zn pressure and annealing temperature. Optical transparency of the ZnTe crystal increased after annealing. This is because scatter of the incident light by Te inclusions decreased. (© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Crystal growth of Bi2TeO5 by a double crucible Czochralski method

Single crystals of bismuth tellurite (Bi2TeO5) were grown by a double crucible Czochralski method at different pulling and rotation rates, ranging from 0.1mm/h to 0.8mm/h and from 5rpm to 20rpm, respectively. The crystallized phase was verified by X-ray diffraction measurements, occurring structural defects were characterized, and the growth conditions were studied being determined the better parameters to growth good-quality single crystals with uniform pale yellow coloration. Optical band gap of 3.1eV was determined from the optical transmission spectrum.

Growth of square Si single bulk crystals with large side-face widths using noncontact crucible method

The noncontact crucible method was used to prepare square Si single bulk crystals. The size of the square part of the ingots was determined by the side-face width of the four-cornered pattern that appeared on the top surface. We obtained square Si single crystals with sizes of 9.4 × 9.7 and 10.9 × 11.0 cm2 that had no fan-shaped {110} faces and had diagonal lengths of up to 91% of the crucible diameter. To obtain large square Si single bulk crystals with a large side-face width using the present method, the importance of establishing a larger low-temperature region in the Si melt while maintaining a smaller initial temperature reduction was considered.

Growth of MgO doped near stoichiometric LiNbO3 single crystals by a hanging crucible Czochralski method using a ship lockage type powder feeding system assisted by numerical simulation

MgO doped near stoichiometric LiNbO3 (MgOSLN) crystals have great potential for use in periodically poled structured LiNbO3 (PPLN) for doubling frequency lasers and optical parametric oscillation infrared lasers, because of their high optical damage threshold, single domain characteristics, and very low coercive field. However, few MgOSLN crystals are commercially available in the present market because of the great difficulty in growing them. This paper describes how a hanging crucible Czochralski technique with a newly-designed ship lockage type powder feeding system assisted by numerical simulation was developed for the successful growth of high quality near stoichiometric LiNbO3 (SLN) and MgOSLN (~1 mol%) crystals. The physical properties of the crystals were assessed by measuring their crystallinity, Curie temperature, optical properties, coercive field and thermal properties. These properties, including a coercive field of 1.4 kV mm−1 and a thermal conductivity of 6.61 W (m K)−1 demonstrated that the crystals meet the demands for manufacturing periodically poled crystal devices. This growth method has great potential in the mass production of SLN and other incongruently melting crystals.

Highly surface-textured and conducting ZnO:Al films fabricated from oxygen-deficient target for Cu(In, Ga)Se2 solar cell application

Highly conducting ZnO:Al (AZO) films are normally prepared through substrate heating and post-annealing in reducing atmosphere, which is deleterious to maintain the high transparency of films and the overall so­lar cell performance. Here we fabricate AZO films through one-step sputtering at room temperature using oxygen-deficient targets prepared via double crucible method. The best-performed AZO film achieves a low resistivity of 4.4 × 10-4 . cm, a high haze factor of 35.0%, and optimizes the efficiency of Cu (In, Ga)Se2 solar cell with a high value of 14.15%. This letter demonstrates that oxygen deficiency can induce high surface texture, conductivity, and boost solar cell performance.

Effect of Potassium Oxide Addition on Viscosity of Calcium Aluminosilicate Melts at 1673–1873 K

We investigated the changes induced in the viscosities of CaO–SiO2–Al2O3–K2O melts (CaO/SiO2 molar ratio = 0.68 ± 0.04, Al2O3 content = 13.4 ± 0.6 mol%) with the addition of K2O in amounts of 0–17.4 mol% for temperatures of 1673–1873 K using the rotating crucible method. The viscosity increased with an increase in the K2O content when K2O/Al2O3 molar ratio < 0.7. On the other hand, the viscosity decreased with the addition of K2O for K2O/Al2O3 molar ratio > 0.9. The maximum values of the viscosities were noticed in the range of 0.7 < K2O/Al2O3 molar ratio < 0.9. This behavior could not be explained on the basis of the polymerization degree of the aluminosilicate network structure. The 17O magic angle spinning nuclear magnetic resonance (MAS NMR) spectrum of the 31.6CaO-44.2SiO2-13.4Al2O3-10.8K2O (mol%) glass suggested that K+ ions preferentially compensate the negative charge of AlO4, while the Ca2+ ions primarily create non-bridging oxygens (NBOs). The viscosity data and the 17O MAS NMR spectrum also suggested that the increase in viscosity for K2O/Al2O3 molar ratio < 0.7 was because of the increase in the average bond strength of the aluminosilicate framework, which was attributable to the substitution of Ca2+ ions by K+ ions at the charge compensator sites. The activation energies for viscous flow indicated that the NBOs bonded with K+ ions, forming NBO-K species, for K2O contents greater than those corresponding to the viscosity maxima. Thus, the viscosities of aluminosilicate melts are indicative of the average bond strengths of the melts.

Thermographical Analysis of Continuing Tradition of Mirror Casting in Kerala

Additions of large amounts of tin to copper lead to high tin bronzes with interesting combination of properties. Such high tin bronzes need to be carefully processed to avoid brittleness in compositions corresponding to beta and delta phases. The latter has been used in China, India, Korea and Japan to produce distortion free mirror images. This investigation is concerned with the bronze mirror from India where the tradition has survived in the village Aranmula in Kerala. The alloy has an exceptionally high tin content consisting almost entirely of the delta phase, which is an intermetallic compound (Cu31Sn8) of composition 32.6% tin. This is an ideal alloy to be polished into a mirror due to the silvery white color and high hardness. Its high brittleness is offset by an ingenious casting and polishing process. In addition to studying the composition and the casting involving a mould cum crucible method, thermographic analysis has been employed to follow the solidification sequence by looking at the thermal profile. It is correlated with the actual composition, processing parameters and the resultant microstructure, due to the cooling rate the alloy solidifies with a mild departure from the equilibrium phase diagram. Some observations regarding the structure of the delta phase which is a Hume-Rothery phase will be provided about its optical and mechanical properties.

Formation process of Si3N4 particles on surface of Si ingots grown using silica crucibles with Si3N4 coating by noncontact crucible method

A noncontact crucible method was used to investigate the process by which a Si3N4 coating material forms Si3N4 particles or precipitates on the surface of Si melts and ingots. Si ingots were grown using crucibles with and without a mixture of α- and β-Si3N4 particles. The oxygen and nitrogen concentrations in the ingots were measured by Fourier transform infrared spectrometry analysis. The nitrogen concentration in the ingots grown using crucibles with a Si3N4 coating was significantly higher than that in ingots grown using crucibles without a Si3N4 coating because the nitrogen from the Si3N4 coating material dissolved into the Si melt. From orientation image maps analyzed using electron backscattering diffraction patterns of SixNy particles on the surface of the ingots, it was clarified that most of the SixNy particles were β-Si3N4. This was also confirmed by X-ray diffraction measurements. The Si3N4 particles on the surface of the ingots had several morphologies such as needle-like, columnar, leaf-like, and hexagonal structures. There were two cases in which floating Si3N4 particles were formed on the surface of the Si melts, i.e., the removal and dissolution of the Si3N4 coating material. The removed or dissolved Si3N4 coating materials, which consisted of a mixture of α- and β-Si3N4 particles, are considered to have finally changed into β-Si3N4 in the form of transformers or precipitates on the surface of the Si melt, and these β-Si3N4 particles became attached to the surface of the ingots.

Growth of KTN crystals by double crucible Czochralski method

Potassium tantalite niobate (KTa1−xNbxO3, KTN) single crystals with various compositions and sizes were grown by double crucible Czochralski method in KTaO3–KNbO3 solid solution system. All the crystals we have grown are in good transparence and are >1 cm in size. Growth habit, morphological, structural and homogeneity properties of five different compositions of KTN crystals, including KTaO3, KTa0·91Nb0·09O3, KTa0·81Nb0·19O3, KTa0·75Nb0·25O3 and KTa0·63Nb0·37O3, are investigated in this work. Electron probe microanalysis shows that the composition fluctuation of KTN crystal is <0·0003 cm−1. X-ray diffraction experimental results show that all crystals belong to cubic phase at room temperature. Lattice parameters a are 3·984∼3·994 Å, which corresponded to the composition of x = 0∼0·37. High resolution XRD measurement shows that all KTN crystals are in high integrity and good quality. Our work shows that the KTN crystals we have grown are in good quality and have a broad application prospects.

Microstructure of the Nialv Alloys Subjected to the Hpt Deformation

Some attention in physical metallurgy is devoted to the mechanisms of decomposition of the disordered phases via eutectoid transformation accompanied by the atomic ordering. In case of the non-pearlitic modes of transformation this concerns intermetallic phases of the general description A3B-A3C. The application of intensive deformation like HPT may introduce opposite mechanisms introducing some degree of the metastable disordered phase structure at room temperature. The paper presents results of the phase composition and microstructure studies of the alloys of composition Ni75AlxVy (where x =15, 10, 5 and y =10, 15, 20), which undergo the solid-state eutectoid decomposition at temperature 1281 K, in the equilibrium conditions. The alloys achieved by the cold crucible levitation method were later intensively deformed with the method of high pressure torsion (HPT). The alloys after HPT revealed homogenous, metastable L12 (Ni3Al) structure in place of the eutectoid product L12-D022. The average size of the Sherrer’s coherent diffraction volumes did not exceed 9 nm, suggesting nano-structure of the material. Transmission electron microscopy (TEM) and high resolution electron microscopy (HRTEM) revealed that the micro- and nano- deformation twins were the main feature of the microstructure, dividing volume into cells of the sizes similar to the coherent volumes. The HPT deformation did not influence atomic order. The results are compared with those achieved for the injection cast samples.

Growth of Si single bulk crystals with low oxygen concentrations by the noncontact crucible method using silica crucibles without Si3N4 coating

A noncontact crucible method using conventional silica crucibles for reducing stress in Si bulk crystals is proposed. In this method, the Si melt used has a low-temperature region in its upper central part so that natural Si crystal growth occurs inside it. Compared with the conventional growth method, the present method has several merits such as the convex shape of the interface in the growth direction, the possibility of obtaining large ingots even with the use of a small crucible because of the growth in the large low-temperature region, and the small convection in the Si melt due to the existence of the low-temperature region. When using crucibles without Si3N4 coating, p-type Si single bulk crystals can grow inside the Si melt without touching the crucible wall. The single bulk crystals grown have low dislocation densities (on the order of 103cm−2). The diameters of the ingots obtained using a crucible with 30 or 33cm diameter are 21−22cm. The surface orientation of the cross section is (100). An n-type ingot with Σ3 twin grain boundaries is grown using a crucible without Si3N4 coating. The average minority carrier lifetime of a cross section is 82.8μs for the passivated surface of an n-type wafer, which is higher than those (7.3–16.0μs) in the case of p-type wafers. A larger temperature reduction is required for the growth using crucibles without Si3N4 coating than that for the growth using crucibles with Si3N4 coating to obtain ingots with the same diameter. A crystal diameter, as large as 72% of the crucible diameter is obtained for the p-type single bulk crystal grown using crucibles without Si3N4 coating.

Physicochemical Properties of Sb, Sn, Zn, and Sb–Sn System

AbstractThe physicochemical properties, viscosity, density, and surface tension, were measured using the discharge crucible method (DC) on five alloys of Sb–Sn. The performance of the DC method was demonstrated with measurements on pure metals Sb, Sn, Zn, and comparisons with the corresponding literature data. The results reported in this study are for Sb–Sn alloys containing (10, 20, 25, 50, and 75) at% of Sb at 550 K to 850 K. The results show that all the physicochemical properties decrease with decreasing temperature and increase with increasing Sb content in the alloy. The experimentally measured surface-tension values are compared with the Butler model. Several models for viscosity are compared and discussed.

Physicochemical Properties of Sn-Zn and SAC + Bi Alloys

Applying the discharge crucible (DC) method, the viscosity, density, and surface tension were determined for Sn-9Zn and Sn-2.92Ag-0.4Cu-3.07Bi (SAC + Bi) alloys. For comparison, the dilatometric, maximum bubble pressure, and capillary flow methods were used for measurements of these same physicochemical properties for the Sn-2.92Ag-0.4Cu-3.07Bi (SAC + Bi) alloy. The measurements were performed for Sn-9Zn and SAC + Bi alloys in the temperature range from 513 K to 723 K and 530 K to 1180 K, respectively. The experimental data obtained show that addition of Bi to SAC increases the density and decreases the surface tension and viscosity in comparison with SAC solder. Additionally it was found that the properties studied by different methods (maximum bubble pressure, dilatometric, capillary flow, and discharge crucible) were almost identical.

Growth of high-quality multicrystalline Si ingots using noncontact crucible method

Conventional crystal growth methods using silica crucibles cannot control the stress caused by expansion due to the solidification of the Si melt because crucible walls made of silica have insufficient flexibility to reduce the stress. In the case of crystal growth using a silicon nitride crucible, it was reported that an ingot can be more easily released from the crucible. A noncontact crucible method was proposed using conventional silica crucibles that reduces the stress and number of dislocations in Si multicrystalline ingots. We used the present method to grow wafers with only twin boundaries. An ingot with several grains and twin boundaries was realized using a crucible that had not been coated with Si3N4 particles. Several important characteristics were reported such as the presence of a low-temperature region in the Si melt, the possibility of growing large ingots with a diameter close to the crucible diameter, the minority carrier lifetime, the distribution of dislocations, the O concentration and the effect of Si3N4 particles on the crystal structure. Dislocations were almost undetectable in a large area of the cross section when a necking technique was used for the seed growth. The O concentration in ingots grown using crucibles coated with Si3N4 particles was lower than that in an ingot grown using a crucible without a coating of Si3N4 particles. A large ingot with a diameter of 25cm was obtained using a crucible with a diameter of 33cm.

Investigation on the Alkali Resistance Property of Theoretical Composition Magnesia Alumina Spinel Bricks

Using alumina-rich MgAl2O4 spinel AR78 and 97 fused magnesite as raw materials, brine as the binder, magnesia alumina spinel bricks close to theoretical composition have been prepared. The phase composition and microstructure of the specimens were analyzed and characterized. The alkali resistance property of specimens was researched using static crucible method. The erosion mechanism of alkali vapor to specimens was studied by XRD, SEM and EDS. The results show that: (1) The alkali resistance property of MgAl2O4 spinel bricks were improved obviously when the addition of magnesite is more than 7%. (2) The alkali resistance property of MgAl2O4 spinel bricks is the best when the addition of magnesite is 10.3%.

The Reaction between Alkali Vapor and the Theoretical Composition MgAl&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;

The theoretical composition was made from MgO-rich MgAl2O4 (MR66) and alumina powder. The static crucible method was used to study alkali-resistance of the block samples. It has been observed that alkali steam permeated into the hole and reacted with corundum particles that produced β-Al2O3 by means of XRD, SEM and EDS. It led to volume expansion, cracks and melting erosion of corundum particles. The specimen of the 32% content of MgO has good physical and chemical properties and excellent alkali erosion performance. So the specimen is suitable for oxy-fuel combustion for glass melting furnace.