Table of Content

15 April 2025, Volume 54 Issue 4

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Research Articles

In-Situ Diagnosis of Lithium Niobate Crystal Growth Interface Flipping Phenomenon

JIANG Xianlong, ZHENG Weitao, ZHU Yunzhong

2024, 54(4):  533-542.  doi:10.16553/j.cnki.issn1000-985x.2024.0248

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During Czochralski crystal growth, interface flipping is a frequent and concealed destructive phenomenon that induces interface instability and accumulate defects, ultimately degrading crystal quality. However, even for the widely-used Czochralski method, the interface flipping of a growing boule is unobservable. Therefore, presenting interface flipping process in the extreme high-temperature and sensitive crystal growth environment is crucial for understanding crystal growth, optimizing growth process, and hence improving crystal quality. Herein, benefitting from the time series analysis of growth interface electromotive force (GEMF), the interface flipping process during lithium niobate crystal growth was observed; and the quantitative relationship between GEMF trajectory and heat and mass transfer during interface flipping was revealed. Our GEMF method, applicable to the widely used melt growth furnace, provides real-time determination for interface flipping and offers feedback for interface control as well.

Properties of Gadolinium Gallium Garnet Substituded with Different Stoichiometric Ratios of Ca²⁺/Mg²⁺/Zr⁴⁺

SHAO Meifang, FENG Jinyang, HOU Tianjiang, MA Xiao

2024, 54(4):  543-552.  doi:10.16553/j.cnki.issn1000-985x.2024.0233

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Substituted gadolinium gallium garnet (SGGG) crystal is an important substrate material for liquid-phase epitaxial growth of magneto-optical single crystal thin films. SGGG crystals with uniform structure and stable physical properties are the basis for the preparation of magneto-optical single crystal thin films. This article reports the preparation of four different Ca²⁺/Mg²⁺/Zr⁴⁺ doped gadolinium gallium garnet crystals using the Czochralski method.The X-ray rocking curve test shows that the prepared crystals are high crystallinity without twinning, and full width at half maximum (FWHM) is 2.04′, 2.07′, 1.85′, 1.98′, respectively, the lattice constant is 12.440 4~12.481 8 Å. The number of dislocation density is 53~161 cm^-2. The surface roughness of crystal surface (111) measured by atomic force microscopy (AFM) ranges from 0.123 nm to 0.244 nm. The thermal expansion coefficient of the crystal is 8.27×10^-6~8.64×10^-6. The crystal has good transmittance in the wavelength range of 500~2 500 nm. SGGG crystals prepared by adjusting the doping amount of Ca²⁺/Mg²⁺/Zr⁴⁺ can meet the performance requirements of substrate materials for epitaxial growth of magneto-optical single crystal thin films.

Preparation and Properties of Large Size Cs₂LiYCl₆：Ce Crystal

ZHAO Meili, SUN Taofeng, GAO Fan, GONG Hongying, ZANG Xiaowei, GUI Qiang, ZHANG Chunsheng

2024, 54(4):  553-559.  doi:10.16553/j.cnki.issn1000-985x.2024.0210

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In this paper, a series of 3-inch (1 inch=2.54 cm) diameter Cs₂LiYCl₆：Ce (CLYC：Ce) crystals with LiCl molar ratios of 55%~60% were grown by vertical Bridgman method. XRD patterns of opaque initial end of the crystals show that the Li-rich group distribution ratio can effectively inhibit the generation of the Cs₃YCl₆ phase. The optimal molar ratio of LiCl for high quality CLYC is 57%, where the volume ratio of CLYC phase to the total ingot is the largest, and isometric complete length up to 80 mm. Scintillation properties such as relative light output, energy resolution and figure of merit (FOM) of 76 mm×76 mm CLYC：Ce crystal obtained under the optimal proportioning condition were tested. The results show that 4.88% energy resolution is measured at 662 keV of ¹³⁷Cs γ rays. The figure of merit (FOM) of pulse shape discrimination (PSD) measured with a ²⁴¹Am-Be neutron source is 4.18. The study indicates that CLYC：Ce crystal has excellent neutron-gamma discrimination performance.

Effect of Residual Stress and Electric Field on Indentation Hardness of 4H-SiC Surface

ZHU Xingjie, ZHANG Ping, ZUO Dunwen

2024, 54(4):  560-568.  doi:10.16553/j.cnki.issn1000-985x.2024.0255

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The 4H-SiC samples with different surface residual stress states were obtained by lapping. The residual stress on the sample surface was measured by a laser Raman spectrometer, and the indentation hardness of the sample surface without and with electric field was measured by a microhardness tester. The results show that, compared to the state with no residual stress, the sample surface indentation hardness increases by up to 9.5% under a residual stress state ranging from -1.6 GPa to 0 GPa. After a certain current is applied to the sample, the indentation hardness of the sample surface with no residual stress can be reduced by about 6%, and the indentation hardness of the sample surface with residual stress can be reduced by about 13%. The surface indentation hardness of 4H-SiC with different residual stress ranging from -1.6 GPa to 1.6 GPa was simulated by finite element analysis. It is found that the residual tensile stress in the range of 0 GPa to 1.6 GPa can reduce the indentation hardness of the wafer surface by up to 5.8%. The mapping relationship between the residual stress, electric field, and the indentation hardness of 4H-SiC surface is obtained, providing a theoretical basis for reducing the surface hardness of the workpiece by regulating the residual stress and applying an electric field.

Effect of C/Si Ratio on SiC Fast Homoepitaxial Growth in Vertical Hot-Wall CVD Reactor

CHEN Danying, YAN Long, LUO Jiahao, ZHENG Zhenyu, JIANG Yong, ZHANG Kai, ZHOU Ning, LIAO Chenzi, GUO Shiping

2024, 54(4):  569-580.  doi:10.16553/j.cnki.issn1000-985x.2024.0247

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The homoepitaxial growth mechanism of SiC was studied using both experiment and computational fluid dynamics (CFD) simulation in a vertical hot-wall CVD reactor with high-speed wafer rotation, and the influence of the C/Si ratio on the epitaxial growth rate and carrier doping concentration on the wafer surface were explored. The study reveals that the molar ratio of carbon-containing to silicon-containing species above the wafer surface (referred to as the effective C/Si ratio) deviates from the C/Si ratio at the gas inlet. This discrepancy is believed to be related to the gas species redistribution during the gas transport and diffusion, as well as parasitic deposition of precursors in the gas injector and/or on the hot-wall. The impact of the effective C/Si ratio on the growth rate and doping concentration was investigated. It is demonstrated that the growth rate, doping concentration and their uniformities are primarily influenced by the effective C/Si ratio at the wafer surface rather than the C/Si ratio at the gas inlet. By optimizing the growth conditions, high-quality 6-inch (1 inch=2.54 cm)epitaxial wafer is achieved with thickness and doping uniformity of 1.15% and 2.68%, respectively. 8-inch SiC epitaxial wafer with similar thickness and doping uniformities is obtained. Moreover, SiC epilayer (thickness exceeding 50 μm) with high growth rate is also demonstrated.

Improving Low-Frequency Sound Transmission Loss of Double-Layer Panels with a Perforated Sandwich Structure with Porous Lining

LI Wenjing, TIAN Junhong, LI Rensheng, LI Jianing, SUN Xiaowei

2024, 54(4):  581-588.  doi:10.16553/j.cnki.issn1000-985x.2024.0226

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To improve the insufficient sound insulation performance of double-layer panel structures at the mass-air-mass resonance frequency, a double-layer panel acoustic metamaterial consisting of a perforated sandwich plate with a porous liner and a homogeneous plate was designed, and the normal sound transmission loss of the structure was calculated by the finite element method. The numerical results show that when the frequency of the perforated sandwich panel with porous lining is tuned to the resonance frequency of the double-layer panel panel, the reduction of the sound transmission loss caused by mass-air-mass resonance is significantly improved. At the same time, the excellent acoustic isolation performance of the conventional double-layer panel structure is maintained at high frequencies. By comparing the sound absorption coefficient and sound transmission loss of perforated sandwich panels and unperforated sandwich panels, it is found that the excellent sound transmission loss of the double-layer panel acoustic metamaterials is attributed to the sound absorption characteristics of the perforated sandwich panels, which is further verified by changing the frequency of the acoustic absorption and the acoustic properties.

Flexural Waves Band Gap Analysis and Control in Metamaterial-Based Periodic Pipeline Systems

LI Xiaoshuang, JIANG Shuai, GUO Zhenkun

2024, 54(4):  589-597.  doi:10.16553/j.cnki.issn1000-985x.2024.0253

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Pipeline systems are widely used in industrial fields. To effectively control the vibration of the pipes, a periodic pipeline structure with a single degree-of-freedom resonator was designed in this paper, and the propagation characteristics of flexural waves were investigated. The dispersion relationship between the transmission constant and frequency was derived using the transfer matrix method combined with Bloch’s theorem, and the bandgap results were verified through finite element simulation. The results indicate that there are three bandgaps and three passbands within the frequency range of 0~250 Hz, with the first passband having a very narrow frequency range, the second and third passbands having a wider frequency range. In order to interpret the influence of pipeline parameters on transmission characteristics, the control variable method was used to analyze parameters such as unit cell length, pipe thickness, and inner diameter size. The results indicate that an increase in the unit cell length leads to a reduction in bandgap width, while increases in pipe thickness and inner diameter result in an expansion of bandgap width. Finally, to achieve control over the passbands, a single degree-of-freedom resonator was introduced to effectively control specific passbands, and the optimal installation position of the resonator was determined through finite element analysis. The results show that the resonator significantly reduces the width of the passbands. This study provides theoretical support for vibration control of pipeline structures, and can be applied to the design of low-frequency vibration isolation.

Weak Scratch Segmentation Algorithm for Rough Grinding Surface of BGO Crystal Based on Improved U-Net

TAO Wenfeng, ZHANG Xiaolong, ZHU Haibo

2024, 54(4):  598-604.  doi:10.16553/j.cnki.issn1000-985x.2024.0249

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BGO crystals usually need to be cut, grind and other rough machining steps to make the grinding surface to improve the performance of components. The extraction and pre-inspection of scratch defects in the rough machining process are very important for the quality evaluation of subsequent crystal components. However, the traditional industrial machine vision algorithm is difficult to finely segment the weak scratches on the rough grinding surface of crystal, which greatly affects the detection efficiency of the subsequent crystal quality. To address the issue of accurately segmenting weak scratches on the crystal grinding surface, this paper adopts an improved U-Net deep learning algorithm. The algorithm embeds a lightweight CBAM attention mechanism into the U-Net architecture to enhance the network’s ability to extract shallow scratch features and recover details. Meanwhile, the Copy-paste data augmentation method is employed to improve the generalization of the algorithm model. In addition, in order to alleviate the negative impact of foreground background imbalance in the sample, the loss function adopts Dice Loss and Focal Loss composite multi-loss function. Experimental results show that the proposed algorithm effectively and accurately segments the weak scratches on the rough grinding surface of the crystal, achieving Miou value of 85.2% and accuracy value of 95.4%, which represents an improvement over traditional industrial machine vision algorithms. Furthermore, the algorithm alleviates the issues of false segmentation and under-segmentation of weak scratches to some extent, enabling the pre-detection of scratch defects in the rough machining process, and ultimately reducing unnecessary processes and quality assessment steps in the future, while overall improving the production efficiency of industrial crystal products.

Optoelectronic Properties of CsPbX₃ (X=Cl, Br, I) Regulated by Pd Doping

MIN Yueqi, XIE Wenqin, XIE Liang, AN Kang

2024, 54(4):  605-616.  doi:10.16553/j.cnki.issn1000-985x.2024.0254

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The toxic element Pb in CsPbX₃ limits its widespread application in the field of solar cells. Doping with the metal element Pd to replace Pb is an effective approach to reduce its toxicity while also modulating its optoelectronic properties. This study employs first-principles computational methods to analyze the effects of Pd doping on CsPbX₃ (X=Cl, Br, I) in terms of crystal structure, band structure, density of states, and electron localization functions at varying concentrations and orientations. The findings reveal that when Pd is doped into the orthorhombic CsPbX₃ (X=Cl, Br, I), a negative formation energy is achieved, indicating the stability of the structure at room temperature. With the incorporation of Pd, the band edge flattens, the effective mass of charge carriers increases, and the bandgap value decreases. The doping in the <100> orientation has the most significant impact on reducing the bandgap value, and as the concentration of Pd doping increases, the bandgap value of the system continues to decrease. This is attributed to the increased electron localization due to the d-p hybridization effect between Pd and Pb and X. The stronger Pd-X and Pd-Pb bonding at the microscopic level forms local potential wells, enhancing the material's light absorption capacity and photovoltaic conversion efficiency. This results in a significant increase in the absorption coefficient for visible light with wavelengths greater than 600 nm, expanding the visible light absorption range of the doped material. Additionally, Pd doping reduces the Pb content, thereby decreasing the material's toxicity. These findings are instrumental for the design and fabrication of novel perovskite solar cells.

Effect of Strain on Optical Properties of Si Doped A-TiO₂ Studied by the First-Principles

ZHANG Jiaqi, LIN Xueling, TIAN Wenhu, MA Wenjie, ZHANG Xiu, MA Xiaowei, ZHU Qiaoping, HAO Rui, PAN Fengchun

2024, 54(4):  617-628.  doi:10.16553/j.cnki.issn1000-985x.2024.0176

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The effects of strain on electronic structures and optical properties in Si doped anatase TiO₂ (A-TiO₂) were studied by the first-principles calculation based on density functional theory. The results indicate that Si_Ti substitutions cannot improve the optical properties effectively, while Si_O defects can upgrade the absorption amplitude for visible and infrared photons, and cause a redshift in the absorption edge of the optical absorption spectra obviously. The improved optical properties are closely related to electronic structures of Si doped TiO₂ systems. Si_Ti substitutions cannot significantly alter the electronic structure in Si_Ti doped TiO₂, which results in the optical properties of Si_Ti doped system are similar to those of the intrinsic TiO₂ system. However, the impurity levels introduced by Si_O are shallow acceptor levels and locate in the bandgap of TiO₂, which can greatly improve the complex dielectric function in the low-energy region, promoting absorption and photoelectric conversion efficiency of low-energy photons, and therefore enhancing photocatalytic performance of the system. In addition, the optical properties are also related to doping concentration of Si_O, which achieve the best with concentration of 3.7%. On the other hand, the tensile strain of 2% can further increase the absorption amplitude of visible and infrared photons for the system with a doping concentration of 3.7%. Therefore, 3.7% Si dopant and 2% tensile strain in TiO₂may lead to better photoelectric conversion efficiency and photocatalytic activity. The study may provide a path for improving the optical properties of TiO₂ through both doping Si and strain engineering.

First-Principles Study of Multiferroic Properties of V and Cr Doped TiOCl₂ Monolayer

XU Huakai, LAI Guoxia, SU Kunren, XU Xiangfu, CHE Youda, HE Yan, CHEN Xingyuan

2024, 54(4):  629-635.  doi:10.16553/j.cnki.issn1000-985x.2024.0245

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Two-dimensional multiferroic materials with both ferroelectric and magnetic properties show significant applications in next-generation memory storage and spintronics. TiOCl₂ monolayer has potential ferroelectric properties. However, due to the 3d⁰ electron configuration of Ti ions, it exhibits weaker magnetic properties, in order to enhance ferromagnetism, the multiferroic properties of V and Cr doped TiOCl₂ monolayer are calculated by the first-principles simulations in this paper. The results demonstrate that double-site doping with V ions favors the formation of a spatially dispersed structural configuration, leading to an electronic structure characterized by antiferromagnetic coupling while maintaining a high ferroelectric polarization strength in the system. In the case of Cr ion double-site doping, analysis of spin charge density and Bader charge reveals that the two Cr ions form a nearest-neighbor Cr—O—Cr ferromagnetic coupling, TiOCl₂ monolayer achieves the coexistence of strong ferromagnetism and high-speed iron polarization, and the bandgap also shows a decreasing trend due to Cr doping. These findings provide a reference for extending the TiOCl₂ monolayer to achieve multiferroic behavior.

Surface Structure and Electromagnetic Properties of Heusler Alloy Mn₂CoAl(100)

WEN Lin, JIANG Ling, GU Yuxin, DU Xin, SHEN Guangxian, WU Bo

2024, 54(4):  636-642.  doi:10.16553/j.cnki.issn1000-985x.2024.0275

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In this paper, the magnetic properties of Heusler alloy Mn₂CoAl bulk and the atomic relaxation, magnetism, electronic structure and surface atomic polarization behavior of Mn₂CoAl (100) surface were systematically studied by first-principles calculations. Atomic relaxation calculations reveal that the MnAl termination exhibits interlayer differential displacement characteristics: Mn atoms in the first layer relax inward toward the termination while Al atoms shift outward toward the vacuum layer, atoms in the second layer collectively migrate toward the vacuum layer, and those in the third layer display an inward contraction tendency. The remaining three terminations, MnCo, MnMn and CoCo, follow similar patterns, with all three atomic layers in each termination showing slight outward displacements toward the vacuum layer. Notably, no significant deformation occurs in the overall structures of all four terminations. The half-metallic gaps at the MnCo and CoCo terminations of Mn₂CoAl(100) are destroyed by the surface state, while the MnAl and MnMn terminations are not significantly affected and have larger half-metallic gaps, retaining about 92% and 80% of the polarization, respectively, which is predicted to have a superior potential for possible applications in tunnel junctions.

Preparation of Li₂Mg₃TiO₆：Eu³⁺ Red Phosphors and Its Application in White LED

LI Pengcheng, ZHOU Jun, WANG Weigang, WU Kunyao, LI Zhao

2024, 54(4):  643-651.  doi:10.16553/j.cnki.issn1000-985x.2024.0234

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Li₂Mg₃TiO₆：Eu³⁺ red phosphor was synthesized by high-temperature solid-phase method. The phase structure was analyzed by X-ray diffractometer (XRD); the microscopic morphology was characterized by scanning electron microscope (SEM); the optical properties of the powders were tested by fluorescence spectrometer (PL). The results show that the crystal structure of Li₂Mg₃TiO₆：Eu³⁺ did not change after Eu³⁺ doping; the sample particles are uniformly distributed with an average particle size of 2.8 μm; the optimal excitation peak of Li₂Mg₃TiO₆：Eu³⁺ is located at 398 nm, the strongest emission peak is located at 617 nm, and the optimal doping concentration is 7%. The luminescence intensity maintained 60% of its initial intensity at 500 K due to its stable thermal ability. CIE chromatic coordinate of (0.327 4, 0.328 8),and a color rendering index (CRI) of 80. Combined with commercially available phosphors in a certain ratio to obtain light-emitting diode (LED) devices, Li₂Mg₃TiO₆：Eu³⁺ red phosphors have potential applications in white LED.This red phosphor can be applied to the LED devices excited by near-ultraviolet chip.

Afterglow Performance Optimization of Dy³⁺ Doped SrAl₂O₄：Tb³⁺ Afterglow Luminescent Phosphors

SHU Jian, LI Shengnan, JIANG Yi, JIA Zhenguo

2024, 54(4):  652-662.  doi:10.16553/j.cnki.issn1000-985x.2024.0261

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SrAl₂O₄：x%Tb³⁺(SAO：Tb, x=0.3, 0.5, 1.0, 2.0, 3.0), SrAl₂O₄：1.0%Tb³⁺, y%Dy³⁺(SAO：Tb/Dy, y=0, 0.5, 1.0, 3.0, 5.0) series of residual luminescent materials were synthesized by high temperature solid phase method under air atmosphere. XRD patterns and SEM images show that the SAO：Tb and SAO：Tb/Dy samples are all pure phase. The excitation spectrum, emission spectrum and afterglow attenuation curves of SAO：Tb show that the afterglow performance are best when the doping concentration of Tb³⁺ is x=1.0. Dy³⁺ co-doping experiments were carried out on SrAl₂O₄：1.0%Tb³⁺, the sample with the better afterglow performance. The excitation and emission spectra intensities of SAO：Tb/Dy series samples indicate that there may be exist energy transfer (ET) processes in SAO：Tb/Dy phosphors. The afterglow attenuation curves further verify that the number of traps increase after Dy³⁺ co-doping. Comparision with thermoluminescence curves intensities between SAO：Tb and SAO：Tb/Dy indicate that the number of traps in this material increases due to the inclusion of Dy³⁺, at the same time, after co-doping with Dy³⁺, the energy range between trap 1 and trap 2 is reduced, which makes it easier to release more electrons. Combined with the thermos luminescence curve and the luminaire surface temperature, the electron release temperature of SAO：Tb phosphor trap 2 decrease from 117 ℃ to 97 ℃ while Dy³⁺ are incorporated, so that all the trapped electrons can released rely on the heat from the luminaire, thereby converting some of the thermal radiation into visible light, therefore, the SAO：Tb/Dy phosphors are not only free from the reducing atmosphere in preparation process, but also have potential application value in reducing lighting energy consumption and reducing the thermal radiation of lamp source.

Design, Synthesis and Luminescent Properties of CaMoO₄：Dy³⁺/Sm³⁺ White Phosphors

MENG Xiaoyan, GAN Xin, WANG Chunyang, ZHU Yaoxian, YANG Liusai, WU Lidan, DONG Hongxia

2024, 54(4):  663-673.  doi:10.16553/j.cnki.issn1000-985x.2024.0250

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In this paper, CaMoO₄：xDy³⁺(x=0.01~0.05) and CaMoO₄：0.03Dy³⁺/ySm³⁺(y=0.01~0.05) series phosphors and CaMoO₄ matrix were synthesized by hydrothermal method using hexadecyl trimethyl ammonium bromide as complexing agent. The effects of Dy³⁺ doping and Dy³⁺/Sm³⁺ co-doping on the structure, morphology and luminescent properties of the samples were investigated. The results show that Dy³⁺ doping and Dy³⁺/Sm³⁺ co-doping do not change the tetragonal phase of CaMoO₄, but the lattice parameters decrease. The micromorphologies of all samples are ellipsoidal. Under the excitation of 353 nm, the strongest emission peak of CaMoO₄：xDy³⁺ phosphor is located at 575 nm, which is due to the ⁴F_9/2→⁶H_13/2 dipole transition of Dy³⁺, and the optimal doping molar concentration is x=0.03. Under the excitation of 298 nm, the quenching molar concentration of Sm³⁺ in CaMoO₄：0.03Dy³⁺/ySm³⁺ phosphor is y= 0.03. The intrinsic emission of rare earth Dy³⁺ and Sm³⁺ are obtained through CaMoO₄ matrix energy transfer, and the energy transfer of Dy³⁺ to Sm³⁺ is also observed. Under the excitation of 405 nm, the CIE coordinates of CaMoO₄：0.03Dy³⁺/ySm³⁺(y=0.01~0.05) change from cyan region to white region, and the CaMoO₄：0.03Dy³⁺/ySm³⁺(y=0.03~0.05) phosphors exhibit white emission. Therefore, Dy³⁺/Sm³⁺ co-doped CaMoO₄ phosphor is a single matrix white LED phosphor with potential application value.

Synthesis and Luminescence Properties of Tb³⁺, Sm³⁺ Doped Color-Tunable KSrGd(WO₄)₃ Phosphors

WANG Yuan’e, WANG Jing, GE Caixia, FU Guojuan, SONG Mingjun

2024, 54(4):  674-683.  doi:10.16553/j.cnki.issn1000-985x.2024.0150

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A series of Tb³⁺ and/or Sm³⁺ doped KSrGd(WO₄)₃ phosphors were prepared by the high temperature solid-state reaction. The structure, morphology, luminescence properties and energy transfer mechanisms were also investigated. Under the excitation of 260 and 405 nm, KSrGd(WO₄)₃：Tb³⁺ and KSrGd(WO₄)₃：Sm³⁺ phosphors give rise to an intense green and orange red emission, respectively. And the optimal concentration of Tb³⁺ and Sm³⁺ in KSrGd(WO₄)₃ phosphors are 0.7 and 0.08, separately. After that, the luminescence intensity gradually decreases with increasing of doping concentration, due to the concentration quenching effect. In KSrGd(WO₄)₃：xTb³⁺ and KSrGd(WO₄)₃：ySm³⁺ samples, the types of energy transfer between activator ions are dipole-quadrupole and dipole-dipole interaction, respectively. When Sm³⁺ were co-doped in KSrGd(WO₄)₃：Tb³⁺ phosphors,the characteristic emissions of both Tb³⁺ and Sm³⁺ can be observed.Furthermore, as increasing concentration of Sm³⁺, the emission intensities of Tb³⁺ decreases, while those of Sm³⁺were enhanced. The experimental results show that there are not only energy transfer from WO^2-₄ to Tb³⁺ and Sm³⁺, but also energy transfer from Tb³⁺ to Sm³⁺, in Tb³⁺ and/or Sm³⁺ doped KSrGd(WO₄)₃ phosphors. The fluorescence lifetime analysis of Tb³⁺ further confirmed the energy transfer from Tb³⁺ to Sm³⁺. On the basis of CIE calculation, the color of phosphor can be adjusted by fixing the doping concentration of Tb³⁺ and changing the concentration of Sm³⁺ without changing the excitation wavelength. These above results confirm that the synthesized KSrGd (WO₄)₃： Tb³⁺, Sm³⁺phosphors may have potential application prospects for white light-emitting diodeds.

Synthesis, Characterization and Properties of Two Coppper(Ⅱ) Complexes Derived from 4-Amino-2,6-Dimethoxypyrimidine

XU Tongtao, WAN Hongshan, YANG Tianxing, GAO Min, WANG Chong

2024, 54(4):  684-692.  doi:10.16553/j.cnki.issn1000-985x.2024.0185

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Two new copper(Ⅱ) complexes [Cu(amp)Lx](ClO₄)₂(x=1, 2) were synthesized by self-assemble of 4-amino-2,6-dimethoxypyrimidine(amp), organic polyamine N-(2-aminoethyl)-1,3-propylamine) (L1), (bi(3-aminopropyl)-amine (L2) and copper salt using the solvent method. The products were characterized by means of elemental analysis, infrared spectroscopy, ultraviolet spectroscopy, powder X-ray diffraction, and scanning electron microscopy. The crystal structure of [Cu(amp)L2](ClO₄)₂ was analyzed by single crystal X-ray diffraction. The results indicates that [Cu(amp)L2](ClO₄)₂ belongs to monoclinic system, space group P2₁/c with a=1.207 90(12) nm, b=1.327 91(13) nm, c=1.390 39(14) nm, a=90°, b=90.056(3)°, γ=90°. In addition, the fluorescence spectrum shows that the ligand amp has an emission wavelength of 387 nm with a strong fluorescence value. However, when the amp coordinates with orgnic polyamines and copper to form a complex, significant fluorescence quenching occurs. This phenomenon indicates that amp interacting with the organic polyamines(L1, L2) have potential functions as fluorescent probes for copper ions. The antibacterial activity of the products in vitro were studied by agar plate diffusion method. The results show that the products have good antibacterial activity against the tested microorganisms.

Crystal Structure and Magnetism of Two Isomorphic Complexes Based on Mixed Ligands

LI Jia, FENG Jing, MIAO Meng

2024, 54(4):  693-699.  doi:10.16553/j.cnki.issn1000-985x.2024.0244

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3,6-di(2-pyridyl)-1,2,4,5-tetrazine (DPTZ) and 4,4’-oxybisbenzoic acid (H₂OBA) were used as mixed ligands to react with Co(II) ions and Cd(II) ions under solvothermal conditions, resulting in the formation of the complexes[Co(OBA)(DPTZ)]·(DMF)_0.5 (1) and [Cd(OBA)(DPTZ)]·(DMF)_1.5 (2). The structural characterization and analysis of the complexes were conducted through single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, and thermogravimetric analysis. Crystallographic data reveals that complexes 1 and 2 are isostructural, belonging to the monoclinic system with the space group of P2₁/c with each asymmetric unit consisting of onemetal ion (Co/Cd), one 3,6-di(2-pyridyl)-1,2,4,5-tetrazine ligand and one 4,4’-oxybisbenzoic acid ligand. The central metal ion (Co/Cd) has a distorted octahedral configuration, and two adjacent metal ions (Co/Cd) are connected by carboxylic acid ligands, forming a dinuclear pinwheel secondary structural unit. The dinuclear pinwheel secondary structural units are connected by OBA and DPTZ ligands, resulting in an infinitely extended 2D wave-like layer. The existence of the V-shaped ligand OBA as a flexible component within the structure gives rise to both left-handed and right-handed helical chains and helical channels. Furthermore, the magnetic measurement result shows that intramolecular antiferromagnetic interaction is observed in complex 1.

Relationship Between Microstructures of High Concentration Sodium Chloride Aqueous Solutions and Crystals Formed from Them

BAI Shiyu, ZHAO Xingyu, LIN Jiawei, QUAN Guoqiang, WANG Lina

2024, 54(4):  700-707.  doi:10.16553/j.cnki.issn1000-985x.2024.0198

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In order to investigate the relationship between microstructures of inorganic electrolyte aqueous solutions and crystals formed from them, the high concentration sodium chloride aqueous solutions were researched by molecular dynamics simulation based on Lammps software and the results are discussed in combination with those of low concentration sodium chloride aqueous solutions and potassium chloride aqueous solutions. The water molecules are modelled by the SPC/E model and the interactions between particles is described by Coulomb interactions and Lennard Jones potentials. The mass fraction of sodium chloride is 28.21% in the solution, pressure and temperature are 1 atm (1 atm=101.325 kPa) and 380 K, respectively. The analysis results of ion clusters show that the composition and the geometric relationship of the crystals formed from the electrolyte aqueous solution correspond to those of the ion clusters in the solution, indicating that the composition and the geometric structure of the crystals formed from the solution already exist in the parent phase solution and that the crystals have a corresponding relationship with the microstructure of the solution. The results of the radial distribution functions, distances between ions and snapshots show that only directly-contacting ion-pairs and partially-spaced ion-pairs exist in the high-concentration sodium chloride aqueous solution, corresponding to the first and second peaks of Na⁺-Cl^- radial distribution functions in turn. Compared with the results of the low-concentration sodium chloride aqueous solution, the proportion of directly-contacting ion-pairs and that of partially-spaced ion-pairs respectively increases and decreases significantly while completely-spaced ion-pairs disappear, indicating that the pairing mode of ions would change with solution concentration; the transformation of the pairing mode of ions is the reason for the variation of the microstructure of solutions and for that of the structure of the crystals formed from solutions. The existence of pure water clusters composed of water molecules and ion clusters composed of Na⁺ and Cl^- in the solution states that the self-concentration effect is presented in the high-concentration sodium chloride aqueous solution. The results in this paper could provide an insight into the understanding crystallization and microscopic structure of solutions.

Theoretical Study of Ni-MoTiNO for Electrochemical N₂ Reduction Reaction

CAO Qi, CUI Luyao

2024, 54(4):  708-716.  doi:10.16553/j.cnki.issn1000-985x.2024.0242

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The electrochemical nitrogen reduction reaction (ENRR) is one of the sustainable development technologies for the synthesis of NH₃ to replace the Haber-Bosch process. The core issue is to find stable electrocatalysts with high catalytic activity and selectivity. Since the transition metal oxynitrides (TMNO) surface follows the Mars-van Krevelen (MvK) mechanism pathway for ammonia synthesis reaction, it exhibits more favorable N₂ adsorption and activation than the conventional association mechanism. Based on this, Ni was selected to be loaded on dual-sites MoTiNO with the best ENRR performance, and the Ni-MoTiNO structure was constructed as an electrochemical N₂ reduction catalyst by the density function theory (DFT) calculation method, and four aspects, including the structural stability, two-site adsorption behaviors, ENRR catalytic activity based on the ^*H-migration-assisted MvK mechanism, and the analysis of the electronic properties, were investigated. Results show that the synergistic action of the dual sites (Ni and Nv) on the surface of Ni-MoTiNO both promotes ^*H migration and effectively breaks the linear proportionality between the strong adsorption of ^*N-related intermediates and the difficulty in resolving the products in ENRR. Experiments have proved that the synthesized Ni-MoTiNO can effectively achieve ammonia synthesis and has a relatively high selectivity.

Research Letter

Preparation of 4-Inch High-Quality GaN Single Crystal Substrates

QI Zhanguo, WANG Shouzhi, LI Qiubo, WANG Zhongxin, SHAO Huihui, LIU Lei, WANG Guodong, SUN Defu, YU Huidong, JIANG Kaize, ZHANG Shuang, CHEN Xiufang, XU Xiangang, ZHANG Lei

2024, 54(4):  717-720.  doi:10.16553/j.cnki.issn1000-985x.2025.4001

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In this study, the porous substrate and stress control techniques were adopted to successfully break through the dislocation suppression and stress control problems in the growth of heterogeneous epitaxial GaN single crystals, and high-quality GaN single crystals with a diameter of 4-inch were prepared. After cutting, chamfering, grinding, and chemical-mechanical polishing, a damage-free, ultra-smooth 4-inch self-separating GaN single crystal substrate with a thickness of 500 μm was obtained. The substrate has both excellent crystalline quality and mechanical stability, with uniform surface color, no cracking phenomenon, and uniform stress distribution; cathodoluminescence spectroscopy (CL) measurements reveal a dislocation density of 9.6×10⁵ cm^-2, and the rocking curve of high-resolution X-ray diffraction (HRXRD) (002) is as low as 57.91″; the surface roughness Ra<0.2 nm measured by atomic force microscope (AFM), presenting atomic-level flat surface. The as-prepared substrate is ready-to-use, meeting the requirements for blue/green laser diodes and power electronic devices.