Study on the cracking of a KDP seed crystal caused by temperature nonuniformity

CrystEngComm ◽  
2018 ◽  
Vol 20 (23) ◽  
pp. 3171-3178 ◽  
Author(s):  
Pingping Huang ◽  
Shenglai Wang ◽  
Duanliang Wang ◽  
Hui Liu ◽  
Guangxia Liu ◽  
...  
Keyword(s):  
Temperature Difference ◽  
Seed Crystal ◽  
Growth Solution ◽  
Seed Crystals ◽  
Temperature Nonuniformity ◽  
Cut Seed

The phenomenon of the cracking of KDP z-cut seed crystals with a series of sizes due to the temperature difference of the growth solution was explored in detail.

Growth of High Quality 4H-SiC Crystals in Controlled Temperature Distributions of Seed Crystals

2012 ◽  
Vol 717-720 ◽  
pp. 13-16
Author(s):  
Hiroshi Tsuge ◽  
Shinya Sato ◽  
Masakazu Katsuno ◽  
Tatsuo Fujimoto ◽  
Wataru Ohashi
Keyword(s):  
Crystal Surface ◽  
Surface Condition ◽  
Large Diameter ◽  
Growth Conditions ◽  
Seed Crystal ◽  
Seed Crystals ◽  
Temperature Distributions ◽  
Edge Part ◽  
Defect Densities

Large diameter 4H-SiC single crystal wafers with higher quality are required to improve the yields of devices fabricated onto the SiC wafers. For crystal growths with higher quality, it is important to prepare seed crystals with lower defect densities. In particular, the edge part of the seed has to be prepared with considerable care because the crystallinity of the enlarged part of grown crystals depends much upon the surface condition of the seed crystal during radial expansion growth. We found that growth with fewer defect and micropipe densities, specifically at the periphery of the crystal, is possible by utilizing in-situ etching process for the seed crystal surface. We have also performed intense numerical calculations of the temperature distribution around the seed surface, and discussed growth conditions which cause the in-situ etching effective to improvement of the crystallinity in enlarged crystals.

Effect of the Seed Polarity for High Quality 4H-SiC Crystal Grown on 6H-SiC Seed by PVT Method

2011 ◽  
Vol 679-680 ◽  
pp. 44-47
Author(s):  
Im Gyu Yeo ◽  
Tae Woo Lee ◽  
Jong Hwi Park ◽  
Woo Sung Yang ◽  
Heui Bum Ryu ◽  
...  
Keyword(s):  
Growth Rate ◽  
Single Crystal ◽  
Seed Crystal ◽  
Crystal Quality ◽  
High Quality ◽  
Seed Crystals ◽  
Opposite Face ◽  
Crystal Region ◽  
Sublimation Technique

The single crystal ingots by using a sublimation technique were grown on 6H-SiC dual-seed crystals with opposite face polarities and then SiC crystal wafers sliced from the SiC ingot were systematically investigated to find out the polarity dependence of the crystal quality. The growth rate of the SiC crystal grown in this study was about 0.2mm/hr. N-type 2’’ SiC crystals exhibiting the 4H- and 6H-SiC polytype were successfully fabricated on C-face and Si-face, respectively. The incorporation of nitrogen donors in the SiC crystals grown on the C-face seed crystal was exhibited to be higher than in SiC crystals grown on a Si-face crystal. When the SiC crystal ingot proceeded to grow, the SiC crystal region grown on the C-face seed crystal was enlarged compared to the SiC crystal region on the Si-face seed crystal.

Structural Characterization of Lateral-grown 6H-SiC a/m-plane Seed Crystals by Hot Wall CVD Epitaxy

2014 ◽  
Vol 1693 ◽  
Author(s):  
Ouloide Yannick Goue ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
Andrew J. Trunek ◽  
Philip G. Neudeck ◽  
...  
Keyword(s):  
Grown Crystal ◽  
Stacking Faults ◽  
Chemical Vapor ◽  
Growth Direction ◽  
Seed Crystal ◽  
Lateral Expansion ◽  
X Ray ◽  
Seed Crystals ◽  
High Resolution Tem ◽  
Crystal Fibers

ABSTRACTThe performance of commercially available silicon carbide (SiC) power devices is limited due to inherently high density of screw dislocations (SD), which are necessary for maintaining polytype during boule growth and commercially viable growth rates. The NASA Glenn Research Center (GRC) has recently proposed a new bulk growth process based on axial fiber growth (parallel to the c-axis) followed by lateral expansion (perpendicular to the c-axis) for producing multi-faceted m-plane SiC boules that can potentially produce wafers with as few as one SD per wafer. In order to implement this novel growth technique, the lateral homoepitaxial growth expansion of a SiC fiber without introducing a significant number of additional defects is critical. Lateral expansion is being investigated by hot wall chemical vapor deposition (HWCVD) growth of 6H-SiC a/m-plane seed crystals (0.8mm x 0.5mm x 15mm) designed to replicate axially grown SiC single crystal fibers. The post-growth crystals exhibit hexagonal morphology with approximately 1500 μm (1.5 mm) of total lateral expansion. Preliminary analysis by synchrotron white beam x-ray topography (SWBXT) confirms that the growth was homoepitaxial, matching the polytype of the respective underlying region of the seed crystal. Axial and transverse sections from the as-grown crystal samples were characterized in detail by a combination of SWBXT, transmission electron microscopy (TEM) and Raman spectroscopy to map defect types and distribution. X-ray diffraction analysis indicates the seed crystal contained stacking disorders and this appears to have been reproduced in the lateral growth sections. Analysis of the relative intensity for folded transverse acoustic (FTA) and optical (FTO) modes on the Raman spectra indicate the existence of stacking faults (SFs). Further, the density of stacking faults is higher in the seed than in the grown crystal. Bundles of dislocations are observed propagating from the seed in m-axis lateral directions. Contrast extinction analysis of these dislocation lines reveals they are edge type basal plane dislocations that track the growth direction. Polytype phase transition and stacking faults were observed by high-resolution TEM (HRTEM), in agreement with SWBXT and Raman scattering.

Effect of β–Si3N4 seed crystal on the microstructure and mechanical properties of sintered reaction-bonded silicon nitride

1999 ◽  
Vol 14 (1) ◽  
pp. 178-184 ◽  
Author(s):  
Soo Young Lee ◽  
K. Amoako-Appiagyei ◽  
Hai Doo Kim
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Silicon Nitride ◽  
High Strength ◽  
Considerable Improvement ◽  
Seed Crystal ◽  
Bimodal Microstructure ◽  
Seed Crystals ◽  
Before And After ◽  
Gas Pressure Sintering

β–Si3N4 seed crystal has been synthesized from α–Si3N4 powder. Reaction-bonded Si3N4/SiC composite has been fabricated with β–Si3N4 seed crystals. The nitridation behavior and the changes in mechanical properties resulting from the addition of seed crystals were studied before and after gas pressure sintering. Addition of seeds showed a considerable improvement in the nitridation, resulting in increase in fracture strength of the composite. Highly nitrided reaction-bonded Si3N4 (RBSN) as a result of the addition of seed crystals gave rise to high strength of composite after postsintering. Fracture toughness of the seeded Si3N4 was also improved up to 35% compared to the baseline Si3N4. Micrographs showed that the seeded Si3N4 developed a bimodal microstructure which resulted in an improvement in fracture toughness.

scholarly journals Al-ZSM-5 Nanocrystal Catalysts Grown from Silicalite-1 Seeds for Methane Conversion

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 485
Author(s):  
Hyun Su Kim ◽  
Su Kyung Kang ◽  
Haoxiang Zhang ◽  
Elsa Tsegay Tikue ◽  
Jin Hyung Lee ◽  
...  
Keyword(s):  
Rapid Growth ◽  
Methane Conversion ◽  
Crystal Size ◽  
Reaction System ◽  
Seed Crystal ◽  
Catalyst Stability ◽  
Synthesis Time ◽  
Seed Crystals ◽  
Synthesis Conditions ◽  
Methane Dehydroaromatization

This study evaluated Al-ZSM-5 nanocrystals grown from silicalite-1 seed crystals as catalysts for the methane dehydroaromatization (MDA) reaction. Silicalite-1 seed crystals sized between 30 and 40 nm were used to grow Al-ZSM-5 under various synthesis conditions. The size of Al-ZSM-5 was significantly affected by the Si/Al ratio (SAR), synthesis time, and silica nutrients/seed crystal ratio (NSR). Larger crystals were obtained with an increased SAR in the synthesis sols. Gradual growth of Al-ZSM-5 occurred with synthesis time, although the growth in crystal size ceased at 5 h of synthesis at 120 °C, indicating the rapid growth of Al-ZSM-5 aided by the silicalite-1 seeds. Precise tuning of Al-ZSM-5 size was possible by changing the nutrient/silicalite-1 seed ratio; a higher NSR led to larger crystals. Two representative Al-ZSM-5 crystals with SARs of 35 and 140 were prepared for catalyst testing, and the crystal sizes were tailored to <100 nm by controlling NSR. The MDA reaction was conducted in the presence of the prepared Al-ZSM-5. The catalyst size exhibited distinct differences in catalyst stability, while the SAR of catalysts did not produce noticeable changes in the catalyst stability of the Al-ZSM-5 crystals and commercial zeolites in this reaction system.

Mg-doped Nd-Ba-Cu-O generic seed crystals for the top-seeded melt growth of large-grain (rare earth)-Ba-Cu-O bulk superconductors

2006 ◽  
Vol 21 (6) ◽  
pp. 1355-1362 ◽  
Author(s):  
Y. Shi ◽  
N. Hari Babu ◽  
K. Iida ◽  
D.A. Cardwell
Keyword(s):  
Rare Earth ◽  
Volume Fraction ◽  
Seed Crystal ◽  
Superconducting Properties ◽  
Seed Crystals ◽  
Bulk Superconductors ◽  
Wide Range ◽  
Single Grain ◽  
Basic Characteristics ◽  
Mg Doped

We report the fabrication of Mg-doped NdBCO generic seed crystals, which have been developed recently for the fabrication of any rare earth (RE) based (RE)-Ba-Cu-O single-grain superconductor, with a wide range of Nd1+xBa2-xCu3-yMgyO7-δ compositions. Three basic characteristics of the seed crystals required for effective seeding of bulk (RE)BCO materials were studied in detail. We report the chemical, crystallographic, microstructural, and superconducting properties of the seeds and demonstrate clearly their potential to process various (RE)BCO superconductors in single-grain form. The melting point, volume fraction of Mg-rich inclusions in the bulk microstructure, and the chemical composition of the Nd1+xBa2-xCu3-yMgyO7-δ superconducting matrix of the seed crystals were studied as a function of initial MgO content. Finally, the suitable range of MgO-content within the generic seed crystal that controls effectively the orientation of the seeded grain without compromising its superconducting properties relative to those of the Mg-free compound is identified based on the wide range of seed crystal compositions investigated.

Polytype and Crystal Quality of SiC Crystals Grown on 3C-SiC by Seeded Solution Method

2009 ◽  
Vol 615-617 ◽  
pp. 27-30 ◽  
Author(s):  
Kazuaki Seki ◽  
Ryo Tanaka ◽  
Toru Ujihara ◽  
Yoshikazu Takeda
Keyword(s):  
Growth Process ◽  
Solution Method ◽  
Grown Crystal ◽  
Stacking Faults ◽  
High Density ◽  
Seed Crystal ◽  
Solution Growth ◽  
Crystal Quality ◽  
Seed Crystals

We investigated the effects of the solution growth process on the polytype and crystal quality of the crystals grown on (111) 3C-SiC seed crystals. In spite of the use of 3C-SiC seed crystals, the polytype of the grown crystal changed from 3C-SiC to 6H-SiC, because the stacking errors easily occur due to the similarity of the (111) face of 3C-SiC and the (0001) face of 6H-SiC. Moreover, the grown 6H-SiC crystal affected the crystal quality of the seed crystal, i.e., high-density stacking faults were induced in the seed crystal after the growth process.

scholarly journals Controlling the Spatial Direction of Hydrothermally Grown Rutile TiO2 Nanocrystals by the Orientation of Seed Crystals

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 64 ◽  
Author(s):  
Julian Kalb ◽  
James Dorman ◽  
Stephan Siroky ◽  
Lukas Schmidt-Mende
Keyword(s):  
Crystal Orientation ◽  
Branching Processes ◽  
Chemical Properties ◽  
Growth Direction ◽  
Seed Crystal ◽  
Tio2 Nanorods ◽  
Tio2 Nanocrystals ◽  
Spatial Direction ◽  
Rutile Tio2 ◽  
Seed Crystals

Hydrothermally grown TiO2 nanorods are a key material for several electronic applications. Due to its anisotropic crystal structure, the electronic properties of this semiconductor depend on the crystallographic direction. Consequently, it is important to control the crystal orientation to optimize charge carrier pathways. So far, the growth on common polycrystalline films such as fluorine tin oxide (FTO) results in randomly distributed growth directions. In this paper, we demonstrate the ability to control the growth direction of rutile TiO2 nanocrystals via the orientation of the seed crystals. The control of the orientation of such nanocrystals is an important tool to adjust the electronic, mechanical, and chemical properties of nanocrystalline films. We show that each employed macroscopic seed crystal provides the growth of parallel nanofingers along the [001] direction under specific angles. The parallel growth of these nanofingers leads to mesocrystalline films whose thickness and surface structure depends on the crystal orientation of the seed crystal. In particular, the structure of the films is closely linked with the known inner structure of hydrothermally grown rutile TiO2 nanorods on FTO. Additionally, comprehensive 1D structures on macroscopic single-crystals are generated by branching processes. These branched nanocrystals form expanded 2D defect planes, which provide the opportunity of defect doping-induced two-dimensional electronic systems (2DES).

Control of Lamellar Orientation in γ-TiAl Based PST Crystal by Using Seed Crystals

2000 ◽  
Vol 646 ◽  
Author(s):  
Y. Yamamoto ◽  
H. Morishima ◽  
K. Koike ◽  
M. Takeyama ◽  
T. Matsuo
Keyword(s):  
Peritectic Reaction ◽  
Single Phase ◽  
Grown Crystal ◽  
Abrupt Change ◽  
Seed Crystal ◽  
Floating Zone ◽  
Zone Method ◽  
Seed Crystals ◽  
Lamellar Orientation ◽  
Crystal Seed

ABSTRACTUnidirectional solidification of Ti-48Al binary alloy using γ-TiAl single-phase seed crystals has been carried out by an optical floating zone method. The lamellar orientation of the grown PST crystal follows the orientation of the Ti-57Al seed crystal, while it fails to follow that in the case of the Ti-53Al seed. Microstructure analysis reveals that the seed crystal of Ti-57Al exhibits a flat liquid/solid interface in melting (γ→+L) even after making contact with 48Al to grow, whereas the seed of Ti-53Al shows a cellular interface due to the peritectic reaction in melting (γ→α+L). At the 57/48 interface, an abrupt change of Al concentration was detected from the seed to the grown crystal, indicating an occurrence of composition travel to skip the peritectic reaction, which is responsible for the control of lamellar orientation of the grown PST crystals. The same attempt has been made by using the 57Al single crystal seed with a different orientation, and the lamellar orientation of the grown PST crystal was confirmed to follow the orientation of the seed.

Effect of Cu(II) on Bio-Scorodite Crystallization Using Acidianus brierleyi

2015 ◽  
Vol 1130 ◽  
pp. 101-104 ◽  
Author(s):  
Naoko Okibe ◽  
Shiori Morishita ◽  
Masahito Tanaka ◽  
Tsuyoshi Hirajima ◽  
Keiko Sasaki
Keyword(s):  
Cell Growth ◽  
Seed Crystal ◽  
Solution Phase ◽  
Seed Crystals ◽  
Acidianus Brierleyi ◽  
Shake Flasks

The effect of different concentrations of Cu (II) on microbial scorodite (FeAsO4⋅2H2O) formation was investigated by using thermo-acidophilic iron-oxidizing archaeon, Acidianus brierleyi. In the presence of 8-16 mM Cu (II) microbial Fe (II) oxidation and cell growth was only marginal. Its As (III) oxidation ability was especially severely inhibited by the presence of Cu (II), consequently disabling scorodite formation. However, when scorodite seed crystals were fed, Ac. brierleyi readily oxidized Fe (II) and As (III) even in the presence of 8.0 mM Cu (II), forming crystalline scorodite within 24 days in shake flasks. All Cu (II) remained in the solution phase during scorodite crystallization, with or without the presence of seed crystals. Increasing the seed crystal concentration (from 0.015 to 0.15%) slightly improved the As immobilization (from 96 to 98%). This study demonstrated that scorodite can be crystallized from the model As (III)-bearing wastewater containing Cu (II).

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