In this work, the possibility of improving 2D electron gas mobility and sheet carrier concentration in AlGaN/AlN/GaN heterostructures by altering GaN/sapphire buffer growth pressure and application of low‐temperature GaN interlayers in GaN buffer is investigated. Obtained results show some improvements in 2DEG resistivity reduction after the introduction of two GaN buffer sublayers grown at different pressures. It is observed that the MOVPE process pressure influences the size of GaN buffer block size visible on the scanning electron microscope images of the AlGaN/AlN/GaN surface. These data are complemented by the results of high‐resolution X‐ray diffraction, photoluminescence, and impedance spectroscopy of the investigated heterostructures.
{"title":"AlGaN/GaN Heterostructures Electrical Performance by Altering GaN/Sapphire Buffers Growth Pressure and Low‐Temperature GaN Interlayers Application","authors":"M. Wośko, B. Paszkiewicz, R. Paszkiewicz","doi":"10.1002/crat.202100090","DOIUrl":"https://doi.org/10.1002/crat.202100090","url":null,"abstract":"In this work, the possibility of improving 2D electron gas mobility and sheet carrier concentration in AlGaN/AlN/GaN heterostructures by altering GaN/sapphire buffer growth pressure and application of low‐temperature GaN interlayers in GaN buffer is investigated. Obtained results show some improvements in 2DEG resistivity reduction after the introduction of two GaN buffer sublayers grown at different pressures. It is observed that the MOVPE process pressure influences the size of GaN buffer block size visible on the scanning electron microscope images of the AlGaN/AlN/GaN surface. These data are complemented by the results of high‐resolution X‐ray diffraction, photoluminescence, and impedance spectroscopy of the investigated heterostructures.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"160 6 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77094085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yanhan Che, Guoqing Feng, Weijun Guo, Jingkun Xiao, Chengwen Song
FeVO4 nanoparticles are synthesized by the hydrothermal method. The effect of micromorphology under different pH conditions is investigated. Their microstructure, morphology, and chemical composition are analyzed by X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, and N2 adsorption–desorption. The results showed that an increase in pH leads to agglomeration of the material. The effect of different pH conditions on the gas‐sensitive performance of FeVO4 is subsequently investigated, and the best response performance of the FeVO4 sensor is achieved at a pH of 3. The consequences showed that the FeVO4 sensor has a response of 3.383 to 100 ppm ethanol gas, with the response and recovery time of 1 and 7 s. The response cycle test has proved that FeVO4 has good stability. Analyzed in conjunction with the characterization results, the oxygen vacancies on the surface of the nanoparticles not only improve the electronic conductivity but also provide active sites for the adsorption of gases, which helps to improve the sensitivity of the material to gases.
{"title":"Synthesis of FeVO4 Nanoparticles and Sensing Performance for Ethanol Gas under Different Solution pH","authors":"Yanhan Che, Guoqing Feng, Weijun Guo, Jingkun Xiao, Chengwen Song","doi":"10.1002/crat.202100110","DOIUrl":"https://doi.org/10.1002/crat.202100110","url":null,"abstract":"FeVO4 nanoparticles are synthesized by the hydrothermal method. The effect of micromorphology under different pH conditions is investigated. Their microstructure, morphology, and chemical composition are analyzed by X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, and N2 adsorption–desorption. The results showed that an increase in pH leads to agglomeration of the material. The effect of different pH conditions on the gas‐sensitive performance of FeVO4 is subsequently investigated, and the best response performance of the FeVO4 sensor is achieved at a pH of 3. The consequences showed that the FeVO4 sensor has a response of 3.383 to 100 ppm ethanol gas, with the response and recovery time of 1 and 7 s. The response cycle test has proved that FeVO4 has good stability. Analyzed in conjunction with the characterization results, the oxygen vacancies on the surface of the nanoparticles not only improve the electronic conductivity but also provide active sites for the adsorption of gases, which helps to improve the sensitivity of the material to gases.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"48 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87237996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Masthead: Crystal Research and Technology 10'2021","authors":"","doi":"10.1002/crat.202170029","DOIUrl":"https://doi.org/10.1002/crat.202170029","url":null,"abstract":"","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"46 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81125517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"(Crystal Research and Technology 10/2021)","authors":"","doi":"10.1002/crat.202170028","DOIUrl":"https://doi.org/10.1002/crat.202170028","url":null,"abstract":"","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"4 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75616493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yanfang Wu, Hao Zhang, Naixing Wang, Tianling Chen, Yan Liu
Valacyclovir hydrochloride is a kind of antiviral drug and has several crystal forms including sesquihydrate (SH), anhydrous Form I, and Form II. Here, the dehydration process of SH by heat drying is investigated by powder X‐ray diffraction, differential scanning calorimetry, thermogravimetry analysis, vapor sorption analysis, and ReactRaman spectroscopy, and the dehydration and absorption of crystal water are revealed. The transformations of SH to Form I, Form II to Form I, and SH to Form II in aqueous ethanol suspension are monitored by ReactRaman spectroscopy, and the mechanisms of two different transition processes are defined through the analysis of ReactRaman spectra. The crystal transformation relationship of the mentioned forms is established.
{"title":"A Study on the Crystal Transformation Relationships of Valacyclovir Hydrochloride Polymorphs: Sesquihydrate, Form I, and Form II","authors":"Yanfang Wu, Hao Zhang, Naixing Wang, Tianling Chen, Yan Liu","doi":"10.1002/crat.202100084","DOIUrl":"https://doi.org/10.1002/crat.202100084","url":null,"abstract":"Valacyclovir hydrochloride is a kind of antiviral drug and has several crystal forms including sesquihydrate (SH), anhydrous Form I, and Form II. Here, the dehydration process of SH by heat drying is investigated by powder X‐ray diffraction, differential scanning calorimetry, thermogravimetry analysis, vapor sorption analysis, and ReactRaman spectroscopy, and the dehydration and absorption of crystal water are revealed. The transformations of SH to Form I, Form II to Form I, and SH to Form II in aqueous ethanol suspension are monitored by ReactRaman spectroscopy, and the mechanisms of two different transition processes are defined through the analysis of ReactRaman spectra. The crystal transformation relationship of the mentioned forms is established.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"17 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82786941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A part consisting of Ni1Cu weathering steel is prepared by wire‐arc additive manufacturing (WAAM). Micro‐ and crystalline structures of this sample are analyzed spectro‐ and microscopically. Mechanical properties of the Ni1Cu steel (including microhardness, tensile strength, and impact resistance) are also assessed. Ni1Cu weathering steel possesses excellent forming quality and almost no defects when used for WAAM. The main features of the steel microstructure are blocks and needles, consisting of ferrite and granular bainite. The microhardness values in the transverse and longitudinal directions are uniform and equal to 169 and 177 HV0.2, respectively. Ni1Cu steel also demonstrates excellent mechanical properties with the transverse yield strength, tensile strength, elongation, and impact value of Charpy impact equal to 379 MPa, 517 MPa, 35.5%, and 147 J at −20 °C, respectively. The longitudinal direction values are equal to 376 MPa, 510 MPa, 31.5%, and 130 J at −20 °C, respectively. The Ni1Cu steel corrosion potential and current are equal to −719 mV and 5.8 × 10−3 mA cm−1, respectively.
{"title":"Wire‐Arc Additive Manufacturing Using Ni1Cu Weathering Steel","authors":"Haitao Zhang, Suisong Wu, Rumeng Shi, Chun Guo","doi":"10.1002/crat.202100118","DOIUrl":"https://doi.org/10.1002/crat.202100118","url":null,"abstract":"A part consisting of Ni1Cu weathering steel is prepared by wire‐arc additive manufacturing (WAAM). Micro‐ and crystalline structures of this sample are analyzed spectro‐ and microscopically. Mechanical properties of the Ni1Cu steel (including microhardness, tensile strength, and impact resistance) are also assessed. Ni1Cu weathering steel possesses excellent forming quality and almost no defects when used for WAAM. The main features of the steel microstructure are blocks and needles, consisting of ferrite and granular bainite. The microhardness values in the transverse and longitudinal directions are uniform and equal to 169 and 177 HV0.2, respectively. Ni1Cu steel also demonstrates excellent mechanical properties with the transverse yield strength, tensile strength, elongation, and impact value of Charpy impact equal to 379 MPa, 517 MPa, 35.5%, and 147 J at −20 °C, respectively. The longitudinal direction values are equal to 376 MPa, 510 MPa, 31.5%, and 130 J at −20 °C, respectively. The Ni1Cu steel corrosion potential and current are equal to −719 mV and 5.8 × 10−3 mA cm−1, respectively.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"81 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80067793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The crystallization process of bis(2‐hydroxyethyl) terephthalate is experimentally investigated. The optimized crystals of bis(2‐hydroxyethyl) terephthalate have the median particle size (D50) of 1300 µm and a perfect crystal habit, and their diameter span reduces from 11.48 (before optimization) to 1.72 (after optimization). The results show that more oxygen atoms at both ends of the crystal are exposed to the crystal surfaces, which make it easy to form hydrogen bonds with free bis(2‐hydroxyethyl) terephthalate. Therefore, the crystal surfaces at both ends grow fastest and tend to disappear eventually.
{"title":"Optimization of the Crystallization Process of Bis(2‐hydroxyethyl) Terephthalate","authors":"Peiquan Yuan, Baoshu Liu, Hua Sun","doi":"10.1002/crat.202100025","DOIUrl":"https://doi.org/10.1002/crat.202100025","url":null,"abstract":"The crystallization process of bis(2‐hydroxyethyl) terephthalate is experimentally investigated. The optimized crystals of bis(2‐hydroxyethyl) terephthalate have the median particle size (D50) of 1300 µm and a perfect crystal habit, and their diameter span reduces from 11.48 (before optimization) to 1.72 (after optimization). The results show that more oxygen atoms at both ends of the crystal are exposed to the crystal surfaces, which make it easy to form hydrogen bonds with free bis(2‐hydroxyethyl) terephthalate. Therefore, the crystal surfaces at both ends grow fastest and tend to disappear eventually.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"6 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72819358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Bohatý, Oliver Lux, H. Eichler, H. Rhee, Alexander A. Kaminskii, Petra Becker
In single crystals of orthorhombic α‐AlOOH, known also as mineral diaspore, χ(3)‐nonlinear lasing by stimulated Raman scattering (SRS) and Raman‐induced four‐wave mixing (RFWM) is investigated. Picosecond pumping at 1.064 µm wavelength produces a broadband Stokes and anti‐Stokes frequency comb with up to 25 SRS‐ and RFWM‐generated emission lines. All observed Stokes and anti‐Stokes lasing components in the visible and near‐IR are identified and attributed to a single SRS‐promoting vibration mode with ωSRS ≈ 445 cm−1. The first Stokes steady‐state Raman gain coefficient in the visible spectral range is estimated to a value not less than 0.36 cm GW−1.
在正交α - AlOOH(也称为矿物一水硬铝石)单晶中，研究了受激拉曼散射(SRS)和拉曼诱导四波混频(RFWM)的χ(3)‐非线性激光。皮秒泵浦在1.064µm波长产生宽带斯托克斯和反斯托克斯频率梳，最多有25条SRS和RFWM产生的发射线。所有观测到的可见光和近红外的Stokes和反Stokes激光分量都被识别出来，并归因于一个单一的SRS促进振动模式，ωSRS≈445 cm−1。在可见光谱范围内的第一个Stokes稳态拉曼增益系数估计不小于0.36 cm GW−1。
{"title":"Stimulated Raman Scattering (SRS) in α‐AlOOH (Diaspore)","authors":"L. Bohatý, Oliver Lux, H. Eichler, H. Rhee, Alexander A. Kaminskii, Petra Becker","doi":"10.1002/crat.202100055","DOIUrl":"https://doi.org/10.1002/crat.202100055","url":null,"abstract":"In single crystals of orthorhombic α‐AlOOH, known also as mineral diaspore, χ(3)‐nonlinear lasing by stimulated Raman scattering (SRS) and Raman‐induced four‐wave mixing (RFWM) is investigated. Picosecond pumping at 1.064 µm wavelength produces a broadband Stokes and anti‐Stokes frequency comb with up to 25 SRS‐ and RFWM‐generated emission lines. All observed Stokes and anti‐Stokes lasing components in the visible and near‐IR are identified and attributed to a single SRS‐promoting vibration mode with ωSRS ≈ 445 cm−1. The first Stokes steady‐state Raman gain coefficient in the visible spectral range is estimated to a value not less than 0.36 cm GW−1.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"37 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90652008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Multicrystalline silicon solar cells occupy 62% in crystalline silicon solar cell production. It is grown by the directional solidification process. Solidification control has a vital role in directional solidification process. Cone shape groove is made in the directional solidification block to enhance the outgoing heat flux in the center region than the peripheral region. Five directional solidification furnaces are simulated for making a multicrystalline silicon ingot. First furnace is the conventional furnace, the second furnace has 30 mm × 85 mm groove block, the third furnace has 40 mm × 85 mm groove block, the fourth furnace has 50 mm × 85 mm groove block and the fifth furnace has 60 mm × 85 mm groove block. The von Mises stress in the maximum volume of the conventional and modified grown ingots are below the range of critical value. In conventional case 7% of the ingot volume is above critical stress value and in the modified cases 2.5% of the ingot volume is above critical stress value. If axial and radial temperature gradient is combined in the 50 mm × 85 mm groove block leads to better results.
{"title":"Numerical Investigation of Cone Shape Grooved DS Block to Improve the mc–Si Ingot Quality","authors":"Aravindan Gurusamy, Srinivasan Manikam, Ramasmy Perumalsamy","doi":"10.1002/crat.202100018","DOIUrl":"https://doi.org/10.1002/crat.202100018","url":null,"abstract":"Multicrystalline silicon solar cells occupy 62% in crystalline silicon solar cell production. It is grown by the directional solidification process. Solidification control has a vital role in directional solidification process. Cone shape groove is made in the directional solidification block to enhance the outgoing heat flux in the center region than the peripheral region. Five directional solidification furnaces are simulated for making a multicrystalline silicon ingot. First furnace is the conventional furnace, the second furnace has 30 mm × 85 mm groove block, the third furnace has 40 mm × 85 mm groove block, the fourth furnace has 50 mm × 85 mm groove block and the fifth furnace has 60 mm × 85 mm groove block. The von Mises stress in the maximum volume of the conventional and modified grown ingots are below the range of critical value. In conventional case 7% of the ingot volume is above critical stress value and in the modified cases 2.5% of the ingot volume is above critical stress value. If axial and radial temperature gradient is combined in the 50 mm × 85 mm groove block leads to better results.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"303 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75426488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vaterite aggregate grooves are successfully obtained by the Ca(OH)2‐CO2 reaction system in the presence of aspartic acid (Asp). Then, the dynamic changes of pH, conductivity, the concentration of Ca2+ and OH– in the suspension during the reaction process are tested. Moreover, the morphologies and polymorphs of the precipitates at different reaction time are studied by the field emission scanning electron microscope (FE‐SEM) and X‐ray Diffraction (XRD). The results show that when Asp is not added in the Ca(OH)2 suspension, the precipitates are calcite, while the carbonization precipitates with Asp are vaterite. Furthermore, in the presence of Asp, the carbonization process in the Ca(OH)2 suspension has a coating‐fragmentation behavior, and vaterite aggregate grooves can be formed after 110 min. In particular, Asp plays an important role in the nucleation, crystallization, and growth of CaCO3, and then a novel formation mechanism of vaterite aggregate grooves is proposed in this paper.
{"title":"Formation and Stabilization of Vaterite Aggregate Grooves with Aspartic Acid (Asp) by Bubbling CO2 into a Ca(OH)2 Suspension","authors":"Tianwen Zheng, Haihe Yi","doi":"10.1002/crat.202100136","DOIUrl":"https://doi.org/10.1002/crat.202100136","url":null,"abstract":"Vaterite aggregate grooves are successfully obtained by the Ca(OH)2‐CO2 reaction system in the presence of aspartic acid (Asp). Then, the dynamic changes of pH, conductivity, the concentration of Ca2+ and OH– in the suspension during the reaction process are tested. Moreover, the morphologies and polymorphs of the precipitates at different reaction time are studied by the field emission scanning electron microscope (FE‐SEM) and X‐ray Diffraction (XRD). The results show that when Asp is not added in the Ca(OH)2 suspension, the precipitates are calcite, while the carbonization precipitates with Asp are vaterite. Furthermore, in the presence of Asp, the carbonization process in the Ca(OH)2 suspension has a coating‐fragmentation behavior, and vaterite aggregate grooves can be formed after 110 min. In particular, Asp plays an important role in the nucleation, crystallization, and growth of CaCO3, and then a novel formation mechanism of vaterite aggregate grooves is proposed in this paper.","PeriodicalId":10797,"journal":{"name":"Crystal Research and Technology","volume":"11 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83098172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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