Papers by Keyword: Crucible

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Authors: Myung Yoon Um, Ho Keun Song, Hoon Joo Na, Dae Hwan Kim, In Bok Song, Sang Yong Jung, Jae Kyeong Jeong, Jae Bin Lee, Hyeong Joon Kim
Authors: S. Siegel, M. Hermann, G. Putzky
Authors: Hee Jun Lee, Hee Tae Lee, Hee Won Shin, Mi Seon Park, Yeon Suk Jang, Won Jae Lee, Dong Yeob Kim, Soon Ku Hong, Jung Gon Kim
Abstract: Aluminum nitride (AlN) bulk crystals, approximately 50.8mm in diameter and up to 5mm thickness, were grown by a physical vapor transport (PVT) method in a tantalum crucible. To investigate the effect of crucible materials, various crucible materials, a graphite and TaC-coated graphite and tantalum crucible were used for the AlN growth. XRD pattern of AlN crystal grown on SiC seed in the Ta-crucible exhibited only (00l) peaks, indicating that AlN single crystal was successfully grown on SiC seed. The interface structure between AlN and SiC crystals was observed by a high resolution TEM.
Authors: Martin C. Schubert, Jonas Schön, Alireza Abdollahinia, Bernhard Michl, Wolfram Kwapil, Florian Schindler, Friedemann Heinz, Milan Padilla, Johannes A. Giesecke, Matthias Breitwieser, Stephan Riepe, Wilhelm Warta
Abstract: This work presents recent advances in the characterisation of carrier recombination and impurities at Fraunhofer ISE. The role of iron contamination during crystallisation is analysed in more detail. Numerical simulations and comparisons to experimental data are presented which demonstrate the impact of iron from the crucible and crucible coating and show the in-diffusion of iron into the silicon melt as well as into the solid silicon during crystal cooling. Measurements of spatially resolved carrier lifetime and interstitial iron concentration on wafers after phosphorus diffusion gettering are used as input for cell efficiency modelling which reveals the specific and quantitative role of iron on cell parameters in multicrystalline silicon. A new photoluminescence based method is presented which quantitatively determines the interstitial iron concentration in finished solar cells. We finally present advances in defect characterisation with sub-micrometre resolution: We show recent progress in micro photoluminescence spectroscopy for the quantitative measurement of interstitial chromium with high spatial resolution. A further development of this setup will be discussed: By combining the principle of Light Beam Induced Current (LBIC) or voltage (LBIV) and the highly localized illumination, images of carrier recombination at local defects are presented which feature a, compared to EBIC, higher signal-to-noise ratio.
Authors: Chi Kwon Park, Joon Ho An, Won Jae Lee, Byoung Chul Shin, Shigehiro Nishino
Abstract: A sublimation epitaxial method, referred to as the Closed Space Technique (CST) was adopted to produce thick SiC epitaxial layers for power device applications. We aimed to systematically investigate the dependence of SiC epilayer quality and growth rate during the sublimation growth using the CST method on various process parameters such as the growth temperature and working pressure. The etched surface of a SiC epitaxial layer grown with low growth rate (30 μm/h) exhibited a low etch pit density (EPD) of ~2000 /cm2 and a low micropipe density (MPD) of 2 /cm2. The etched surface of a SiC epitaxial layer grown with a high growth rate (above 100 μm/h) contained a high EPD of ~3500 /cm2 and a high MPD of ~500 /cm2, which indicates that high growth rate aids the formation of dislocations and micropipes in the epitaxial layer.
Authors: Fernando Gomes, Joaquim Barbosa, Carlos Silva Ribeiro
Abstract: During the last years a very significant effort to develop a melting crucible for induction melting of Ti based alloys at competitive cost has been carried out by many researchers, where the authors are included. Results obtained so far have shown that no material accomplishes the melting crucibles two main demands: inertness facing titanium alloys and suitable/enough thermal-shock resistance. Until now, yttrium and calcium oxides were those materials that performed best on what concerns to thermodynamic stability. However, in both cases, crucibles thermal-shock resistance was very poor, and there are references to crucibles that cracked during melting. Besides, calcium oxide reveals manipulation problems, due to its high higroscopicity. This paper concerns to the evaluation of zircon based crucibles with Y2O3 inner layer for induction melting of TiAl based alloys. A novel multi layered crucible production technique based in a centrifugally assisted slip casting process followed by a sintering operation is described, and results concerning to crucibles porosity and wall composition and morphology are presented. Crucibles obtained in different processing conditions were used to melt a Ti48Al alloy which was poured in graphite moulds. Experimental results include alloy chemical contamination with residual elements, mainly yttrium and oxygen, microhardness measurement and the presence of yttrium oxide and zircon inclusions in the cast samples. Results concerning to the crucibles behaviour are also presented with particular attention to cracks development. The Y2O3 crucible layer was found to suffer some erosion and be slightly dissolved by the molten alloy and the extent of those phenomena depends on the porosity of the layer surface, for fixed experimental melting conditions.
Authors: Kap Ryeol Ku, Jung Kyu Kim, Jung Doo Seo, Ju Young Lee, Myung Ok Kyun, Won Jae Lee, Geun Hyoung Lee, Il Soo Kim, Byoung Chul Shin
Abstract: SiC single crystal ingots grown by sublimation physical vapor transport (PVT) technique were prepared and then the SiC crystal quality with varying crucible design employing a guide tube and tantalum foil was systematically investigated. The growth rate of 2-inch SiC crystal grown by these crucible designs was about 0.3 mm/hr. The n-type and p-type 2”-SiC single crystals exhibiting the polytype of 6H-SiC were successfully fabricated. The doping concentration level of below ~1017/cm3 was extracted from the absorption spectrum and Hall measurement. The densities of micropipes and inclusions in SiC crystal boules grown using the graphite/Ta foil double layer guide tube were significantly decreased. Finally we improved crystal quality through the introduction of new crucible design.
Authors: Ting Ting Sun, Min Jiang, Chong He Li, Xiong Gang Lu, Wei Dong Liu
Abstract: CaO is a promising refractory for melting TiNi shape memory alloys, the carbon contamination can be avoid by using CaO crucible instead of carbon crucible. However, its industrial application is limited by the easy hydration of CaO in the air. In this study, the hydration resistance of CaO is modified by the addition of ZrO2, the powder of CaO adding 6.0 to 15.0mol% ZrO2 and 2.0mol% TiO2 is ball- milled, the mixture is shaped into the chip by the isostatic pressing method (IP), then the samples are sintered at 1750°C. The X-ray diffraction analysis reveals that the sintered samples consist of CaO dissolved with ZrO2 and CaZrO3. The anti-hydration property is described by the weight addition of samples, which are stored at the room temperature and atmosphere. It is shown that the sample with 12% ZrO2 of additive possesses the good hydration resistance, its weight addition stored after 56-days is less than 0.6wt%. Therefore, the powder of CaO with 12.0% ZrO2 additive are used to prepare the crucible by IP, the green crucible is sintered at 1750°C. This home-made crucible is used for melting TiNi alloy by means of the induction method at 1500~1800°C temperature and the vacuum environment, it is found that, the internal and external surface of crucible were almost kept unchanged after melting, this refractory did not obviously react with titanium melts, this result may provide a support for searching a new refractory with the good hydration resistance for melting of titanium alloys.
Authors: Feng Feng Li, Jiao Du, Ming Xi Zhang, Wei Chao Yang, Yi Shen
Abstract: Cordierite–mullite composite crucibles were prepared via high-temperature solid-state process by using burn talc, datong soil, knar clay, bentonite, quartz, feldspar and alumina as raw materials, waste porcelain powder as skeletal material. The main influencing factors such as the raw materials radio and calcination temperature were discussed. The microstructure of the sintered sample was analyzed with X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The results show that the optimal prescription was sample II (13.34 wt% of burn talc, 10.496wt% datong soil, 40.65% knar clay, 15.00wt% waste porcelain powder,10.34wt% bentonite, 2.17wt% feldspar, 1.61wt% quartz, and 6.394wt% of alumina). The optimal sintered temperature was 1380°C and the holding time was 3 hours.
Authors: De Zhen Meng, Guang Yao Chen, Ru Lin Zhang, Chong He Li
Abstract: Y2O3 doped SrZrO3(SZY) powders were prepared according to a solid-state reaction method, which the raw materials contains SrCO3, ZrO2 and doped with 5 mol% Y2O3. And then the powders were used to make a green crucible shape by cold isostatic pressing. After that, the crucible was used to melt with TiNi alloy in the vacuum induction furnace with biscuit firing temperature of 900°C, and sintering temperature of 1750°C. The x-ray diffraction analysis (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS) were used to analysis the characterization of the Y2O3 doped SrZrO3 power; microstructure of the crucible at different holding time under the 1750°C and the interfacial reaction between the crucible and the TiNi alloy. The results showed that the powders of Y2O3 doped SrZrO3 were synthesized at 1200°C, and there was no obvious reaction layer and elements diffusion between the crucible and TiNi alloy. The ingot is easy to separate from the crucible after smelting.
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