History of Single-crystal Growth in Korea

This volume of the IOP Conference Series is dedicated to scientific contributions presented at the 20th International Workshop on Advanced Computing and Analysis Techniques in Physics Research (ACAT 2021). In 2021, the motto guiding the scientific program was “AI Decoded: Towards Sustainable, Diverse, Performant and Effective Scientific Computing”. The workshop took place from November 29, 2021 to December 3, 2021 in Daejeon, Korea and virtually through teleconferencing.Due to the ubiquitous travel restrictions, most of the about 600 attendees participated virtually. ACAT is badged as a workshop, rather than a conference, because we believe discussions are a key ingredient. The significant fraction of virtual participation impacted this workshop atmosphere in 2021, despite the tremendous work that the Local Organizing Committee has invested in the successful workshop.To cater to virtual presentations, ACAT 2021 featured a highly focused scientific program with reduced session duration. Nonetheless, the scientific program was rich and varied, bringing together experts of all relevant fields from around the globe. It included fourteen invited presentations, both from High Energy and Nuclear Physics such as on “Normalizing Flows for LHC Theory” and “High Performance Analysis, Today and Tomorrow”, as well as from other fields such as the WHO.The parallel program consisted of three tracks, namely Computing Technology for Physics Research, Data Analysis – Algorithms and Tools, and Computations in Theoretical Physics: Techniques and Methods. These tracks featured 75 oral and 128 poster contributions. The posters were presented in a virtual environment that succeeded in engaging the audience.This was the last edition of ACAT that was unaffected by the Russian invasion of Ukraine and the subsequent statement of support from some Russian Federation Institutes.ACAT 2021 is co-organized by the Institute for Basic Science (IBS), the Korea Institute of Science and Technology Information (KISTI), and Soongsil University. IBS is supported by Grant No. IBS-R016-D1 and Soongsil University is supported by the National Research Foundation (NRF) of Korea Grant No. 2016R1D1A1B02012900. ACAT 2021 would like to thank for the support by the Asia Pacific Center for Theoretical Physics (APCTP), the Daejeon International Marketing Enterprise (DIME), the Korean Physical Society (KPS), Brookhaven National Laboratory, Fermi National Accelerator Laboratory, Thomas Jefferson National Accelerator Facility, and Micron Technology, Inc.List of Local Organizing Committee, Scientific Programming Committee, International Advisory Committee, Co-organizers, Sponsors are available in this Pdf.

Materials in the (Na0.5Bi0.5)TiO3–SrTiO3 system are of interest for use as lead-free piezoelectric actuators due to high electric-field induced strains. Piezoelectric properties may be further improved by growing single crystals but as yet work on single crystal growth in this system is limited. In the present work, single crystals of composition 0.75 (Na0.5Bi0.5)TiO3−0.25 SrTiO3 were grown by solid state crystal growth (SSCG) on [001] SrTiO3 seed crystals and the dependence of crystal growth distance and matrix grain growth on sintering temperature investigated. Electron backscattered diffraction and X-ray diffraction analysis show that the single crystals grow epitaxially on the seed crystals. Energy dispersive spectroscopy indicates that the grown crystals are slightly Na-deficient, while X-ray photoelectron spectroscopy indicates the presence of oxygen vacancies. Single crystal growth distance, mean matrix grain size and grain size distribution as a function of sintering temperature and time are presented. Increasing the sintering temperature increases both single crystal and matrix grain growth rates. The optimum single crystal growth temperature is found to be 1250°C. The effect of sintering temperature on the single crystal and matrix grain growth behavior is explained using the mixed control mechanism of microstructural evolution.

ConspectusPorous materials have wide applications in the fields of catalysis, separation, and energy conversion and storage. Porous materials contain pores that are specifically designed to achieve expectant performance. The solid phases in porous materials are normally completely continuous to form the basic porous frame while the pores are fluid phase within the solid phase. Single crystals are macroscopic materials in three spatial dimensions with the constituent atoms, ions, molecules, or molecular assemblies arranged in an orderly repeating pattern with the ordered structures. The growth of single crystals is indeed a process to arrange these constituents in three dimensions into a repeating pattern within the materials. Today the applications of single crystals are exponentially growing in wide fields, and single crystals are therefore unacknowledged as the pillars of our modern technology. Introducing porosity into single crystals would be expected to create a new kind of porous material in which the basic porous frames are single-crystalline and free of grain boundaries. The structural symmetry is completely maintained within the basic porous frames which are a continuous solid phase, but it is completely lost inside the pores. The porous architecture is free of grain boundaries, and the fully interconnected skeletons are in single-crystalline states within the basic porous frames. Single crystals with porosities can therefore be considered to be a new kind of porous material, but they are single-crystal-like because the structural symmetry is maintained only in the skeletons and completely lost within the pores. We therefore call them porous single crystals or consider them in porous single-crystalline states to stand out with their structural features. Porous single crystals at the macroscale combine the advantages of porous materials and single crystals to incorporate both porosity and structural coherence in a porous architecture, leading to invaluable opportunities to alter the material's properties by controlling the unique structural features to enhance its performance. However, the growth of single crystals in three dimensions reduces the formation of porosities, leading to a fundamental challenge for introducing porosity into single crystals in a traditional process of crystal growth. In this Account, we report the rational design, growth methodology, and microstructural engineering of porous single crystals in a solid-solid transformation. We rationally design a high-density mother phase in a single-crystalline state and transform it into a low-density new phase in a single-crystalline state to introduce porosities into single crystals even incorporating the removal of specific compositions from the mother phase during the growth of porous single crystals. The porosity can be tailored by controlling the change in relative densities from the mother phase to the porous single crystals while the pore size can be engineered by controlling the fabrication conditions. Considering the unique structural features, we explore their functionalities and applications in photoelectrochemical energy conversion, electrochemical alkane conversion, and electrochemical energy storage. We believe that the materials, if tailored into porous single-crystalline states, would not only find a broad range of applications in other fields but also enable a new path for material innovations.

The PZT‐5H single crystal growth on [111]c‐, [110]c‐, and [001]c‐oriented seed crystal by solid‐state crystal growth (SSCG) method was investigated. The growth rate of PZT‐5H single crystal strongly depends on seed crystal orientation and annealing time. The mean growth distance is 682, 620, and 93 μm for [111]c‐, [110]c‐, and [001]c‐oriented PZT‐5H single crystal grown at 1150°C for 8 h, respectively. The growth kinetics of SSCG‐grown PZT‐5H single crystal was discussed. It is found that the growth of single crystal is driven by the solubility difference between the matrix grains and single crystal growth front interface, arising from the local curvature and the crystallographic directions dependent solubility. The growth of [001]c‐oriented PZT‐5H single crystal was mainly contributed from the difference solubility arising from the local curvature of growth front interface, while the growth of [111]c‐ and [110]c‐oriented PZT‐5H single crystal was mainly contributed from the difference solubility between {111} and {110} plane of single crystal and matrix grains. The piezoelectric coefficient d33 of up to 1028pC/N (about 50% larger than that of the same component ceramic) was obtained in a [110]c‐oriented PZT‐5H single crystal with a Curie temperature of about 230°C. The large field piezoelectric constants d33* of up to 1160 pm/V (about 50% larger than that of the same component ceramic) at 15 kV/cm was also obtained in [110]c‐oriented PZT‐5H single crystal with a large strain of 0.18%. This work deepens our understanding on the growth kinetics of SSCG and pushes the way of growth of soft PZT single crystal by SSCG.

The (1−x)(Na1/2Bi1/2)TiO3-xSrTiO3 (NBT-100xST) system is a possible lead-free candidate for actuator applications because of its excellent strain vs. electric field behaviour. Use of single crystals instead of polycrystalline ceramics may lead to further improvement in piezoelectric properties but work on single crystal growth in this system is limited. In particular, the effect of composition on single crystal growth has yet to be studied. In this work, single crystals of (NBT-100xST) with x = 0.00, 0.05, 0.10 and 0.20 were grown using the method of Solid State Crystal Growth. [001]-oriented SrTiO3 single crystal seeds were embedded in (NBT-100xST) ceramic powder, which was then pressed to form pellets and sintered at 1200 °C for 5 min–50 h. Single crystal growth rate, matrix grain growth rate and sample microstructure were examined using scanning and transmission electron microscopy. The results indicate that the highest single crystal growth rate was obtained at x = 0.20. The mixed control theory of grain growth is used to explain the single crystal and matrix grain growth behaviour.

Design and construction of the vertical dynamic gradient freeze (VDGF) system operating in the temperature range from 50 °C to 500 °C for growing organic single crystals are described. The design of VDGF system consists of furnace, control system, translation assembly, and image capturing device. Furnace has been constructed with eight zones controlled independently by a dynamic temperature control system for achieving desired thermal environment and multiple temperature gradients, which are essential for the growth of organic single crystals. The transparent furnace enables direct observation to record and monitor the solid-liquid interface and growth of crystals through charge coupled device based video camera. The system is fully computerized hence it is possible to retrieve the complete growth and furnace history. In order to investigate the functioning of the constructed VDGF system for the growth of organic single crystals, a well known organic nonlinear optical single crystal of benzimidazole was grown. The crystalline quality and the optical transmittance of the grown crystal were studied.

In the present work, the single crystal growth by solid-state crystal growth of (100−x)(K0.5Na0.5)NbO3–xSrTiO3, where x = 0,1,2,3 mol-%, has been examined in order to study the effect of SrTiO3 content on single crystal growth. Powders were prepared by the conventional mixed oxide method. <001> KTaO3 seed crystals were buried in the powders, pressed into pellets and sintered at 1100°C for 1, 3, 5 and 10 h. Single crystals of the ceramic compositions grew onto the seeds. For the (K0.5Na0.5)NbO3 sample, both single crystal growth and abnormal grain growth in the matrix began to take place within 1 h. As the amount of SrTiO3 increased, the onset of both single crystal growth and abnormal grain growth were delayed. The effect of SrTiO3 addition on the single crystal and matrix grain growth behaviour is explained in terms of the mixed control theory of grain growth.

Single crystals of 0.75(Bi1/2Na1/2)TiO3-0.25SrTiO3 have potential for use in piezoelectric actuators because of their large values of electric field-induced strain. Single crystals of 0.75(Bi1/2Na1/2)TiO3-0.25SrTiO3 have been prepared by solid-state single crystal growth, but growing large crystals is difficult due to matrix grain growth. Previous experiments with 0.95(Bi1/2Na1/2)TiO3-0.05BaTiO3 showed that doping with ZrO2 reduced matrix grain growth but also reduced single crystal growth. In this work, 0.75(Bi1/2Na1/2)TiO3-0.25SrTiO3 is doped with small amounts of ZrO2 and the effect on both single crystal and matrix grain growth is examined. ZrO2 addition has a minor effect on single crystal and matrix grain growth.

(K0.5Na0.5)NbO3-based piezoelectric ceramics are of interest as a lead-free replacement for Pb(Zr,Ti)O3. In recent years, single crystals of (K0.5Na0.5)NbO3 with improved properties have been grown by the seed-free solid-state crystal growth method, in which the base composition is doped with a specific amount of donor dopant, inducing a few grains to grow abnormally large and form single crystals. Our laboratory experienced difficulty obtaining repeatable single crystal growth using this method. To try and overcome this problem, single crystals of 0.985(K0.5Na0.5)NbO3-0.015Ba1.05Nb0.77O3 and 0.985(K0.5Na0.5)NbO3-0.015Ba(Cu0.13Nb0.66)O3 were grown both by seed-free solid-state crystal growth and by seeded solid-state crystal growth using [001] and [110]-oriented KTaO3 seed crystals. X-ray diffraction was carried out on the bulk samples to confirm that single-crystal growth had taken place. Scanning electron microscopy was used to study sample microstructure. Chemical analysis was carried out using electron-probe microanalysis. The single crystal growth behaviour is explained using the mixed control mechanism of grain growth. Single crystals of (K0.5Na0.5)NbO3 could be grown by both seed-free and seeded solid-state crystal growth. Use of Ba(Cu0.13Nb0.66)O3 allowed a significant reduction in porosity in the single crystals. For both compositions, single crystal growth on [001]-oriented KTaO3 seed crystals was more extensive than previously reported in the literature. Large (~8 mm) and relatively dense (<8% porosity) single crystals of 0.985(K0.5Na0.5)NbO3-0.015Ba(Cu0.13Nb0.66)O3 can be grown using a [001]-oriented KTaO3 seed crystal. However, the problem of repeatable single crystal growth remains.

Effects of sintering aid and atmosphere powder on the growth of (K0.5Na0.5)NbO3 single crystals fabricated by solid-state crystal growth method

Lanthanide concentrations in 13 fractions of the Norton County achondrite have been determined by a mass spectrometric isotope dilution method. A most remarkable fact is that the distribution of lanthanides is quite different between enstatite single crystal and polycrystalline material. This difference is interpreted in terms of different formation processes. It is thought that in the growth of single crystals, individual ions were placed one by one to build a strictly defined lattice structure, whereas the polycrystalline material was produced by the transitional formation of amorphous phases or phases of low crystallinity resulting from spontaneous cohesion of neighboring ions in the melt. The lanthanide patterns for single crystal fractions are grossly similar to each other, but there is some variation between them in fine structure of the patterns. This can be interpreted as a reflection of the fact that the partition of lanthanides into single enstatite crystals is more or less sensitive to rather subtle differences in the conditions of crystal growth. The genesis of Shalka, Johnstown (both hypersthene achondrites) and eucritic achondrites can be interpreted in terms of the precipitation of single crystals only. A great difference in partition coefficient between single crystals and polycrystalline material system appeares to be of much petrological significance, because it is thought that the difference can also bring about a great difference in efficiency of enrichment of calcium in remnant liquid. Irregular behavior of Cc, Eu, and Yb in a few single-crystal fractions was ascertained by independently processed redeterminations. The irregularities may be ascribed to single crystals favoring higher valence state of these elements relative to the melt. It is suggested that lanthanum might have been a little depleted relative to the other lanthanides in the initial melt that produced Norton County.

Resistive Pulse Sensing of Pre-Nucleation Activities during Single-Entity Lysozyme Crystallization on Single Nanopipettes.

Growth behaviour of potassium sodium niobate single crystals grown by solid-state crystal growth using K 4CuNb 8O 23 as a sintering aid

The influence of excess PbO on Pb(Mg1/3Nb2/3)O3–35mol% PbTiO3{001} single crystal growth by seeded polycrystal conversion (SPC) was studied in the range of 0–10 vol% PbO. As in previous studies, additions of PbO increased the boundary mobility significantly, thus facilitating single crystal growth via SPC. Unlike previous studies, single crystals were grown into pore‐free matrices, resulting in different crystal growth kinetics (signifying interface reaction controlled as opposed to diffusion controlled). Porosity was shown to decrease single crystal growth rates by a factor of 2. Additionally, it was found that single crystal and matrix grain growth rates are optimized at 1.5 vol% PbO, as opposed to previous work, which showed that 3 vol% PbO was fastest. Increasing PbO content beyond 1.5 vol% results in growth that is independent of liquid fraction for all annealing times. In addition, the matrix grains were faceted and the growth best‐fit parabolic kinetics so interface reaction control was deemed the most likely growth mechanism.

The objective of this research project is to produce single crystal niobium (Nb) tubes for use as particle accelerator cavities for the Fermi laboratory’s International Linear Collider project. Single crystal Nb tubes may have superior performance compared to a polycrystalline tubes because the absence of grain boundaries may permit the use of higher accelerating voltages. In addition, Nb tubes that are subjected to the high temperature, high vacuum crystallization process are very pure and well annealed. Any impurity with a significantly higher vapor pressure than Nb should be decreased by the relatively long exposure at high temperature to the high vacuum environment. After application of the single crystal process, the surfaces of the Nb tubes are bright and shiny, and the tube resembles an electro polished Nb tube. For these reasons, there is interest in single crystal Nb tubes and in a process that will produce single crystal tubes. To convert a polycrystalline niobium tube into a single crystal, the tube is heated to within a few hundred °C of the melting temperature of niobium, which is 2477 °C. RF heating is used to rapidly heat the tube in a narrow zone and after reaching the operating temperature, the hot zone is slowly passed along the length of the tube. For crystallization tests with Nb tubes, the traverse rate was in the range of 1-10 cm per hour. All the crystallization tests in this study were performed in a water-cooled, stainless steel chamber under a vacuum of 5 x10-6 torr or better. In earliest tests of the single crystal growth process, the Nb tubes had an OD of 1.9 cm and a wall thickness of 0.15 mm. With these relatively small Nb tubes, the single crystal process was always successful in producing single crystal tubes. In these early tests, the operating temperature was normally maintained at 2200 °C, and the traverse rate was 5 cm per hour. In the next test series, the Nb tube size was increased to 3.8 cm OD and the wall thickness was increased 0.18 mm and eventually to 0.21 mm. Again, with these larger tubes, single crystal tubes were usually produced by the crystallization process. The power supply was generally operated at full output during these tests, and the traverse rate was 5 cm per hour. In a few tests, the traverse rate was increased to 10 cm per hour, and at the faster traverse rate, single crystal growth was not achieved. In these tests with a faster traverse rate, it was thought that the tube was not heated to a high enough temperature to achieve single crystal growth. In the next series of tests, the tube OD was unchanged at 3.8 cm and the wall thickness was increased to 0.30 mm. The increased wall thickness made it difficult to reach an operating temperature above 2,000 °C, and although the single crystal process caused a large increase in the crystal grains, no single crystal tubes were produced. It was assumed that the operating temperature in these tests was not high enough to achieve single crystal growth. In FY 2012, a larger power supply was purchased and installed. With the new power supply, temperatures above the melting point of Nb were easily obtained regardless of the tube thickness. A series of crystallization tests was initiated to determine if indeed the operating temperature of the previous tests was too low to achieve single crystal growth. For these tests, the Nb tube OD remained at 3.8 cm and the wall thickness was 0.30 mm. The first test had an operating temperature of 2,000 °C. and the operating temperature was increased by 50 °C increments for each successive test. The final test was very near the Nb melting temperature, and indeed, the Nb tube eventually melted in the center of the tube. These tests showed that higher temperatures did yield larger grain sizes if the traverse rate was held constant at 5 cm per hour, but no single crystal tubes were produced even at the highest operating temperature. In addition, slowing the traverse rate to as low as 1 cm per hour did not yield a single crystal tube regardless of operating temperature. At this time, it appears that the wall thickness of the Nb tube rather than the operating temperature is the most important parameter to achieving single crystal growth. Single crystal growth was easily obtained with thinner wall tubes, but with thicker tubes, it was not achieved under varied growth conditions.