Table of Content

15 January 2021, Volume 50 Issue 1

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A Crystal Growth Method: Microspacing In-Air Sublimation

YE Xin, LIU Yang, TAO Xutang

2021, 50(1):  1-6. 

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Along with the newly emerging of functional materials such as organic semiconducting crystals and two-dimensional or layered crystals, traditional crystal growth methods for bulk crystals are no more applicable to them. And on the other hand, the invasive procedures like etching in the traditional top-down photolithography are harsh task for these new materials to survive while maintaining integrity to build miniaturized devices. Yang Liu, Xutang Tao, and their colleagues at State Key Laboratory of Crystal Materials, Shandong University have invented a microspacing in-air sublimation (MAS) growth method for such new materials. By creating a gap of a few hundred micrometers between the reservoir of material and the substrate on which the crystals will deposit, it was able to mimic the conditions used in traditional vacuum-based processes, but without any special equipment. The MAS growth is practicable for a wide range of organic and inorganic crystals; besides, it possesses advantages in many aspects such as short growth time, high materials utilization ratio, and applicability for real time observation, etc. Electrical devices based on the micro-crystals grown on the substrate exhibited higher performances than the best record ever reported. The method has aroused much attention in the related fields; and currently it has been adopted by many research groups all around the world.

Research Articles

Low-Frequency Band Gap Characteristics of Phononic Crystal of One-Resonator and One-Resonator with Elastic Support

LI Jing, WANG Hongsai, GUAN Dong, ZHANG Chun, SHEN Hui

2021, 50(1):  7-12. 

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Local resonance phononic crystals can be constructed by adding resonance elements periodically, and low frequency band gap can be generated. In this paper, a phononic crystal composed of one-resonator and one-resonator with elastic support has been presented. The band gap characteristics and band gap regulation characteristics of the structure were calculated and analyzed by using phononic crystal theory and vibration theory. The results show that the initial frequency of the first band gap is 0 Hz. The attenuation of vibration in the band gap is determined by the attenuation factor and period number of the finite structure. There are one tunable band gap and three untunable band gaps in such structure. By changing the structural parameters of one-resonator and one-resonator with elastic support, the tunable band gap can be tuned. The untuable band gaps which include the first band gap can attenuate elastic wave stably. The band gap characteristics of the structure have potential applications in the field of vibration reduction of pipelines, bridges and automobiles.

Lightweight Design and Research of Supercell Phononic Crystal Plate

GUO Zhaofeng, CHEN Chuanmin, QIAO Chuanxi, NI Yuan

2021, 50(1):  13-19. 

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Due to the excellent low-frequency acoustic characteristics of the local resonance type phononic crystal plate, related research is becoming more and more abundant. However, most of them were research in the laboratory environment, and there were insufficient researches on the lightweight of its engineering application. Therefore, based on the application background of low-frequency noise in substations, a lightweight design method for local resonance phononic crystal panels was proposed in this paper. Based on this method, a lightweight supercell phononic crystal plate for substation noise frequency spectrum characteristics was designed. The study found that this phononic crystal plate has obvious sound transmission loss peaks at 50 Hz and 100 Hz, and the sound insulation is 67 dB and 48 dB respectively. The sound insulation mechanism was analyzed and studied through the composite sound intensity streamline diagram of vibration mode displacement and sound pressure level. The research in this paper has guiding significance for the engineering application of phononic crystal plate and the noise control of substations in the future.

Reducing Optical Absorption of ZnGeP₂ Crystal in 1~2.5 μm

ZHAO Xin, XIE Hua, FANG Shenghao, ZHUANG Wei, YE Ning

2021, 50(1):  20-24. 

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ZnGeP₂ crystal has several absorption peaks in 1 μm to 2.5 μm, which are mainly caused by point defect V_P, Ge_Zn and V_Zn. These optical absorption seriously affect the applied performance in optical parametric oscillator. Therefore, theoretical calculation of electron irradiation based on the electron-nucleus scattering theory were executed to understand the effective experiment condition. The ZnGeP₂ single crystal was grown by Bridgman method, then the infrared absorption spectrum, Hall coefficient and carrier concentration of as grown ZnGeP₂, annealed ZnGeP₂ and irradiated ZnGeP₂ were tested by infrared spectrometer and physical performance mearsurement system. The results show that annealed treatment can effectively reduce the optical absorption of ZnGeP₂ crystal near 1.2 μm and 1.4 μm, while electron irradiation treatment is beneficial to reduce the optical absorption of ZnGeP₂ crystal near 2.0 μm, which is consistent with the calculated results.

Temperature-Depending Variation of Lattice of Single Crystal Diamond as Substrate

CHEN Zhengjia, XU Kai, CHEN Guangchao

2021, 50(1):  25-31. 

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The Raman spectrum test was performed on the high temperature and high pressure (HTHP) single crystal diamond as the candidates of the substrates in the CVD(Chemical Vapour Deposition, CVD) epitaxial growth, and the crystalline quality of the substrates was judged by the full width at half maximum (FWHM) of the peak. X-ray in-situ measurement study of the substrate lattice changes during the heating (room temperature to 1 000 ℃) and cooling (1 000 ℃ to room temperature) processes. Experiments show that the lattice constant of the substrate changes with temperature, and the stress caused by the lattice change at 1 000 ℃ is close to the GPa level. The lattice constant is larger in the cooling process than in the heating process, and the same phenomenon is found in the calculation result of the linear expansion coefficient. According to the FT-IR test results of the tested sample, it is inferred that the reason for the variant above-mentioned lattice change is the difference in nitrogen content in the sample. The higher the nitrogen content, the larger the FWHM of the Raman spectrum, and the lattice constant of substrate more obvious changes with temperature, the larger the linear expansion coefficient.

Growth and Magnetic Properties Study of Ultra-Low Saturation Magnetization In∶BiCaVIG Crystal for VHF Applications

WEI Zhantao, YOU Bin, JIANG Fan, ZHANG Pingchuan, LAN Jianghe

2021, 50(1):  32-37. 

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The ultra-low saturation magnetization(M_s) ferrite garnet In∶BiCaVIG single crystal was successfully grown by the accelerated crucible rotation technique. Crystal structure, micro morphology, magnetic properties were systematic investigated. The results show that the In∶BiCaVIG crystal are well crystallized and belong to body-centered cubic structure. The Curie temperature of sample is 104 ℃, the 4πM_s is 60 G and the M_s deviation is±20 G, which are slightly better than similar products of the US Microsphere company. The linewidth(ΔH) of sphere samples reduces obviously by chemical polishing and the minimum ΔH can be up to 5.8 Oe.The behaviour of ΔH is related to the uniform corrosion of the stree layer caused by chemical polishing, which reduces the ΔH value.In addition,the linewidth of ultra-low M_s samples are obviously larger than that of undoped BiCaVIG samples which is mainly related to the contribution of the M_s.

First-Principles Study on the Magnetic and Photoelectric Properties of Mn-Doped ZnTiO₃ with LiNbO₃ Strcture

SU Kunren, LIANG Yiji, LIN Erqing, WANG Guo, XU Xiangfu, CHEN Xingyuan, LAI Guoxia

2021, 50(1):  38-42. 

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The magnetic and photoelectric properties of Mn-doped LN-ZnTiO₃ were calculated through density functional theory. The calculated results show that Mn-doped LN-ZnTiO₃ tends to occupy the Zn site, which forms a stable 3d⁵ electronic configuration. Mn instead of Zn doping in LN-ZnTiO₃ can provide with a large local magnetic moment of about 5 μB. At the same time, an obvious acceptor energy level of Mn-3d and O-2p orbitals are formed near the top of the valence band, which reduces the band gap and promotes the absorption of visible light. Mn doping in LN-ZnTiO₃ could achieve a large local magnetic moment and the characteristics of p-type semiconductor, which expands the application of materials in magnetics and visible light absorption.

Optical Properties of Na⁺, Dy³⁺ and Eu³⁺ Doped YAG Phosphors

LI Qing, WANG Linxiang, BAI Yunfeng, AREPATI Xiakeer

2021, 50(1):  43-52. 

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The Na⁺, Dy³⁺, Eu³⁺ doped YAG series phosphors were prepared by high-temperature solid-phase method. Change the doped Dy³⁺ concentration, excitation wavelength, and doped Na⁺ to study its influence on luminescence. X-ray diffraction results show that the doping of boric acid, Na⁺, Dy³⁺, Eu³⁺ does not affect the cubic phase of YAG, and with the increase of Na⁺, Dy³⁺, Eu³⁺ concentration, the sample diffraction peak position shifts to a small angle. Use λ_em=590 nm to monitor Dy³⁺, 15%Eu³⁺ co-doped YAG powder, with the increase of Dy³⁺ concentration, the excitation intensity of Eu³⁺ and Dy³⁺ both increase first and then decrease. When λ_ex=366 nm is used to excite Dy³⁺, 15%Eu³⁺ co-doped YAG, at this time, there is an energy transfer of Eu³⁺→Dy³⁺, the calculated energy transfer efficiency of Eu³⁺→Dy³⁺ is 84.23%.Compared with 10%Dy³⁺, 15%Eu³⁺ co-doped YAG, the Dy³⁺ luminescence in the sample is enhanced by 1.5 times after doping 0.5%Na⁺, the color coordinate is (0.348 1,0.397), and the color temperature is 5 010 K, which is close to standard white light. When λ_ex=394 nm is used to excite Dy³⁺, 15%Eu³⁺ co-doped YAG, at this time, there is energy transfer from Dy³⁺→Eu³⁺, the calculated energy transfer efficiency of Dy³⁺→Eu³⁺ is 88.9%. Compared with 10%Dy³⁺, 15%Eu³⁺ co-doped YAG, Eu³⁺ luminescence is enhanced 1.8 times after doping 0.5%Na⁺, the color coordinate is (0.466 7, 0.416 8), and the color temperature is 2 650 K, which meets the commercial warm white light standard.

(La_0.95Eu_0.05)F₃ Nanocrystal Synthesized by Sacrificial Template Method and Down-Conversion Luminescence Properties

ZHAO Xinrui, LI Longjiao, GONG Changshuai, WANG Chuqi, MA Teng, WANG Xuejiao

2021, 50(1):  53-59. 

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(La_0.95Eu_0.05)F₃ nanocrystals were successfully prepared from a novel (La_0.95Eu_0.05)₂(OH)₄SO₄·2H₂O template via sacrificial template method, and the down conversion photoluminescence were investigated. The phase and luminescence properties of the synthetic products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) spectroscopy. XRD and Rietveld refinement result indicate that (La_0.95Eu_0.05)₂(OH)₄SO₄·2H₂O template can be obtained using rare earth nitrate and ammonium sulfate as raw materials via hydrothermal reaction at 100 ℃, pH=9.5 for 24 h. The (La_0.95Eu_0.05)F₃ nanocrystals can be successfully synthesized by sacrificial reaction at 180 ℃ for 24 h when the molar ratio of RE³⁺ and F^- is 1∶3 or 1∶5. Photoluminescence analysis show that under 395 nm ultraviolet excitation, the (La_0.95Eu_0.05)F₃ phosphor show down-conversion emission at 591 nm (⁵D₀→ ⁷F₁ transition, strong), 618 nm (⁵D₀→ ⁷F₂ transition, medium strong) and 692 nm(⁵D₀→ ⁷F₄ transition, weak), with color coordinates of around (0.52, 0.45), orange-red light. The strongest emission is found to decay in a single exponential manner and have fluorescence lifetime of 14 ms.

Theoretical Simulation and Analysis of Ultrathin Heterojunction Solar Cells

CHE Jin, LU Haijiang

2021, 50(1):  60-65. 

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The parameters of the window layer and intrinsic layer of the ultrathin heterojunction solar cells were simulate and optimize with AFORS-HET software, such as doping concentration, thickness and band gap, et al. The influence law of each parameter on the performance of the ultrathin heterojunction solar cell was analyzed in combination with the actual situation, and the optimal optimization parameters were obtained. The simulation results show that: for the ultrathin heterojunction solar cell with substrate thickness of only 80 μm, with the increase of the thickness of the window layer, the overall performance of the cell shows a trend of decline. According to the practical situation, the optimal thickness range of the window layer is 5 nm to 9 nm. With the increase of the doping concentration in the window layer, the cell performance as a whole increases first and then tends to be constant. The optimal doping concentration range of the window layer theoretically is 7×10¹⁹ to 8×10¹⁹.The band gap width of the window layer has a great influence on the open-circuit voltage and efficiency of the battery, but has a small influence on the filling factor and short-circuit current. The optimal band gap range of the window layer is 1.85 eV to 2.0 eV.With the increase of the thickness of the intrinsic layer, the FF and efficiency of the cell first increases and then decreases. The short-circuit current gradually decreases while the open-circuit voltage remains basically unchanged. The optimal thickness of the intrinsic layer is 5 nm to 10 nm.When the optical band gap of the intrinsic layer is less than 1.8 eV, it has little influence on the battery performance; when the optical band gap of the intrinsic layer is more than 1.8 eV, the cell performance drops sharply. Therefore, the optimal band gap range of the intrinsic layer is 1.6 eV to 1.8 eV.

Light Injection Study of N-TOPCon Silicon Solar Cells on Annealing Synergies

WEI Kaifeng, LIU Dawei, NI Yufeng, ZHANG Ting, LIU Junbao, ZHANG Tianjie, YANG Lu

2021, 50(1):  66-72. 

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After printing and sintering of the N type TOPCon (Tunnel Oxide Passivating Contacts) solar cells, the efficiency was improved significantly by light injection, which mainly manifested in the improvement of V_oc and FF. The mechanism is to improve the passivation performance through adjusting the Fermi energy level by temperature and light intensity and controlling the total amount and valence state of H. The quality of the passivation film, the doping concentration of silicon substrate and the temperature during the light injection annealing process have great influence on the efficiency of the light injection annealing process. The experiments show that the lower the conversion efficiency of the battery is, the higher the efficiency is after light injection. The higher the conversion efficiency is, the smaller the defect will be, and the efficiency has almost no gain after the light injection annealing process. In addition, concentric circles can be eliminated obviously after light injection annealing process. This paper mainly studies the effects of temperature, light intensity, substrate resistivity, front surface metal contact area and poly-Si thickness on the efficiency of light injection annealing process.

Preparation and Morphology Analysis of Cu₂O Spherulites in DMF System

RAO Shengyuan, QIU Zhihui, XU Jinyan, XU Xin, ZHANG Qi, LONG Ying, RUAN Qingfeng

2021, 50(1):  73-79. 

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Cu₂O spherulites with different morphologies, such as three-dimensional cruciform, hollow and solid Cu₂O spherulites were prepared under DMF solvothermal conditions by changing copper source, surfactant and reaction parameters.The products were characterized by XRD and SEM, and the influences of process conditions on the morphology of Cu₂O spherulites were analyzed. The results indicate that with the increase of DMF concentration, the reduction capacity of the system is enlarged, Cu⁺ increases, and the solution supersaturation is enhanced. The spherulites with anisotropy and symmetry controlled by the crystal structure of Cu₂O crystal aggregates gradually evolve to isotropic spherulites. Surfactants such as sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and polyvinylpyrrolidone (PVP) are beneficial to reduce the supersaturation of the solution, the surface diffusion ability of the crystalline substance is improved. And the formation of Cu₂O grains tends to be regular. In the reaction system, the carboxyl group generated by the hydrolysis of Cu(Ac)₂·H₂O and the formyl group in DMF undergo decarboxylation reaction at high temperature to generate CO₂ gas and the gas generated by SDS foaming is an important reason for the formation of hollow Cu₂O spherulites.

Synthesis of Ultrafine TbO_1.81 and Tb₂O₃ Powders for Magneto-Optical Application

FENG Kai, LÜ Bin, CHENG Hongmei, WU Shaofan, WANG Yan, LIU Yongxing

2021, 50(1):  80-87. 

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Ultrafine TbO_1.81 and Tb₂O₃ powders were obtained from the pyrolytic precursor prepared via a wet chemical route using ammonium hydrogen carbonate (AHC) as the precipitant. The precipitation precursor has a chemical composition of hydrated terbium carbonate and exhibits one-dimensional nanorod morphology. The average width of the nanorods rises as the increase of AHC concentration. Calcining the precursor in air directly yields a round TbO_1.81 nanopowder with an average particle size of ~140 nm through dehydration, decarbonation and particle growth processes. On the other hand, a Tb₂O₃ powder with a finer particle size of ~85 nm is reduced under flowing hydrogen atmosphere upon heating. The molar ratio of AHC to Tb³⁺ significantly affects the particle dispersion of final oxide products and the best molar ratio for the synthesis of well dispersed powder is 1∶1. The bandgap energies of TbO_1.81 and Tb₂O₃ are ~1.67 eV and 5.20 eV, respectively.

Controllable Preparation and UV Detection Performance of ZnO Nanorod Arrays Modified by Conducting Polyaniline Film

WANG Jianchao, YANG Guanghui, TANG Gege, MA Mingyou, PENG Huayong

2021, 50(1):  88-93. 

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Based on the photovoltage effect of p-n junction, UV detectors with excellent performance can be constructed. In this paper, vertically aligned ZnO nanorod arrays (n-type) ZnO-NRs were controllable prepared by hydrothermal method. The p-type polyaniline (PANI-NWs) was modified on the surface of ZnO-NRs by in-situ polymerization, and then assembled into ZnO-NRs and ZnO-NRs/PANI-NWs UV detectors. The morphology, structure and optical properties of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Vis diffuse reflection spectroscopy. The current time (I-t) and current voltage (I-V) curves were measured by electrochemical workstation to characterize the light response properties. The results show that the ZnO-NRs/PANI-NW smaterials are arranged orderly, the interface contact is good, and the pores are uniform. When the ZnO-NRs/PANI-NWs detector detects 365 nm ultraviolet light, the photocurrent can reach 2.73×10^-4 A; at 254 nm, the photocurrent can reach 1.44 × 10^-4A, and its peak value is 4 to 10 times that of ZnO-NRs detector. The increase of photoconductivity is closely related to the p-n junction formed between ZnO-NRs and PANI-NWs. The UV detector assembled with ZnO-NRs/PANI-NWs material shows good stability, fast corresponding speed, short recovery time and high current gain, which provides data support for the development of high performance.

Simulation Analysis of the Effect of Ni and Mo Co-Doping on the Properties of SnO₂

CHANG Yongqiang, WANG Jingqin, ZHU Yancai, ZHANG Guangzhi, HU Delin

2021, 50(1):  94-101. 

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For the deficiencies of AgSnO₂ contact material, the first-principle based on the density functional theory was used to study the electrical and mechanical properties of pure SnO₂, Ni doped SnO₂, Mo doped SnO₂ and Ni-Mo co-doped SnO₂. The parameters of every model, including the formation energy, energy band structure, density of state, elastic constant were obtained by the CASTEP module of Materials Studio software. According to the formation energy, the doped models can exist stably. After doped, every model′s valence band top and conduction band bottom are at the same point so the doped models are still the direct bandgap semiconductor materials. The Ni-doped SnO₂ is P-type doped semiconductor material, and the Mo-doped is the N-type as well as Ni-Mo co-doped SnO₂. With the introduction of the new impurity levels, the band gap is narrowed. Compared with the band structure of pure SnO₂, the doped models have a rising valence band and a declining conduction band so they have a smaller band gap, and the Ni-Mo co-doped SnO₂ has the smallest band gap. With the reduced energy for carrier transition, the electrical performance of SnO₂ is improved largely. What′s more, the shear modulus, volume modulus and hardness are obtained by the elastic constants. The hardness of Ni-Mo co-doped SnO₂ decreases significantly and its toughness is enhanced, which is conductive to the subsequent processing and forming of AgSnO₂ contact material. The Ni-Mo co-doped SnO₂ has the smallest universal elastic anisotropy index so the contact materials are not easy to form cracks. According to the calculation results, it turns out that the co-doping of Ni-Mo can improve the electrical and mechanical properties of SnO₂ better than single element doping, which provides theoretical guidance for the further development and research of contact materials.

Synthesis and Characterization of Copper Naphthoic Acid Phosphonate

BU Kang, JI Yuru, WANG Nan, XU Yang, WANG Xuan

2021, 50(1):  102-105. 

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Self-assembly of phosphonic acid (5-pncH₃=(5-phosphono-1-naphthalenecarboxylic acid) and copper perchlorate hexahydrate, 1D coordination polymer, namely Cu_0.5(5-pncH₂)(H₂O)_1.5 (1) was hydrothermally synthesized. The crystal structure and thermal stability were characterized by single-crystal X-ray diffraction, EA, FT-IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TG-DTG). Structure analyses reveal that compound 1 crystallized in the orthorhombic system, space group Pbcm, a=0.667 88(2) nm, b=0.884 14(2) nm, c=4.174 03(9) nm. Compound 1 has a one-dimensional chain structure, in which the adjacent Cu^II ions are bridged into a one-dimensional zigzag chain through the coordination water molecules. The two-dimensional layered structure is formed by the double hydrogen bond of carboxyl group on the organic phosphonic acid ligand. The thermal stability study shows that the complex exhibits a step-by-step decomposition process, and the stability of the complex skeleton structure can be maintained below 350 ℃.

Synthesis, Single Crystal Transformation and Thermal Stability of Chiral Dysprosium (III)-Tartaric Acid Complex

LI Li, ZHENG Jianfeng, ZHAO Mingxia, FENG Sisi

2021, 50(1):  106-112. 

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The new complex [Dy(Htar)₃(H₂O)₃]_n(1) was synthesized by the single crystal to single crystal transformation method using(+)-di-p-toluoyl-D-tartaric acid (D-H₂DTTA) as raw material and reaction with mentalic Dy(III) salt. The complex was characterized by elemental analysis, IR spectroscopy, single crystal X-ray diffraction, powder X-ray diffraction analysis and thermogravimetric analysis and differential thermal analysis(TGA-DTA). The results of X-ray crystallographic analysis indicate that complex 1 belongs to trigonal system, space group R3 with a=b=2.723 16(14) nm, c=0.762 75(6) nm, α=β=90.00°, γ=120.00°, V=4.898 5 (6) nm³, Z=3, and Cambridge Crystallographic Data Centre (CCDC) number is 1498504. Each Dy³⁺ is surrounded by six O atoms from three Htar^- ligands and three O atoms from three coordinated water molecules, forming a tricapped trigonal prism geometry with nine coordination property. Complex 1 exhibits an infinite one dimensional chain structure connected by O1 and O5 along c axis, with the Dy…Dy distance of 0.762 8(1) nm. Complex 1 was obtained through single crystal to single crystal transformation process from [Dy(HDTTA)₃(CH₃OH)₃]_n, which includes ester hydrolysis and water molecules substitution two reactions. Complex 1 has a certain thermal stability. After taking off the coordinated water molecules in the range of 45~166 ℃, the skeleton of 1 begins to collapse with increasing temperature above 166 ℃.

Preparation of MeCeO_x(Me=In, Zr) Solid Solution Catalyst for the Application in the Synthesis of Dimethyl Carbonate

WANG Yizhou, LIU Fei, ZHAO Tianxiang, CAO Jianxin, XU Fang

2021, 50(1):  113-121. 

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MeCeO_x (Me=In, Zr) bimetallic oxide catalysts were prepared by liquid-phase co-precipitation method with a matrix of CeO₂. The physiochemical properties of MeCeO_x were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction(H₂-TPR), temperature programmed desorption(CO₂-TPD, CH₃OH-TPD), and diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) techniques. Based on the systematic investigation of the types and doping amounts of various metal oxides, the structure properties and catalytic behavior of solid solution catalysts prepared by doping CeO₂ with different metal oxides were comparatively studied in this paper. The results show that the solid solution structure formed by MeCeO_x bimetal oxide catalysts increases the concentration of oxygen vacancy defects. The InCeO_x solid solution catalyst exhibit the largest concentration of oxygen vacancy defects, resulting in the improve chemical adsorption for CO₂ and CH₃OH molecules. Under the condition of reaction pressure 1.0 MPa, reaction temperature 140 ℃, reaction space velocity (GHSV) 3 600 mL/(g·h) and V(CO₂)/V(CH₃OH)/V(N₂)=4∶1∶5, the InCeO_x shows the excellent catalytic performance with dimethyl carbonate selectivity of 91.3%, CH₃OH conversion of 8.4%, and dimethyl carbonate STY(Space Time Yield) of 0.11 g_DMC·h^-1·g^-1_cat. In addition, further in-depth DRIFTS study show that activation of CO₂ with oxygen vacancies and the formation of terminal methoxy as the intermediate are the crucial to the enhance selectivity of dimethyl carbonate.

Photocatalytic Degradation of Toluene by ZnSn(OH)₆/SrSn(OH)₆

PAN Rui, FU Min, CHEN Zhengbo, HU Xueli

2021, 50(1):  122-129. 

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A new type of ZnSn(OH)₆/SrSn(OH)₆ composite photocatalyst was prepared by a simple co-precipitation method. The structure, morphology and light absorption properties of the samples were characterized by XRD, XPS, UV-Vis, N₂ adsorption and desorption, scanning electron microscope(SEM), transmission electron microscope(TEM). Its photocatalytic performance was evaluated by toluene target pollutant. The results show that compared with the pure phase SrSn(OH)₆ and ZnSn(OH)₆, the composite material ZnSn(OH)₆/SrSn(OH)₆ has significantly enhanced ultraviolet light absorption capacity, and the recombination efficiency of photogenerated carriers reduce. Furthermore, the efficiency of photocatalytic degradation of toluene is enhanced. The degradation rate of toluene in the composite sample ZSH/SSH-10(molar ratio is 10%) is more than 58%, which is 1.35 times that of SrSn(OH)₆ monomer. The degradation of toluene for ZSH/SSH-10 catalyst is still 51% after recycling 5 times, indicating that the catalyst has good recycling stability.

Preparation and Photocatalytic Properties of AgBr/TiO₂ Nanofibers

SUN Nan, CHEN Peng, REN Youliang

2021, 50(1):  130-137. 

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AgBr/TiO₂ nanofibers were fabricated by a combination of hydrothermal and electrospinning methods. Ti(OC₄H₉)₄/PVP nanofibers were prepared by electrospinning method using Ti(OC₄H₉)₄, PVP and absolute ethanol as raw materials. TiO₂ nanofibers were obtained after calcination at 500 ℃ to 1 000 ℃. AgBr nanoparticles were immobilized on TiO₂ nanofibers under hydrothermal condition. AgBr/TiO₂ nanofibers were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and differential thermo-thermogravimetric (TG-DTA) analysis respectively. The photocatalytic property of TiO₂ and AgBr/TiO₂ nanofibers were studied using methyl orange(MO) as degradation substrate to simulate dye waste water. The results indicate that the TiO₂ nanofibers with the additive amount of 100 mg have better photocatalytic properties after calcined at 800 ℃. The photocatalytic degradation rate of AgBr/TiO₂ nanofibers is found to be higher than that of the TiO₂ nanofibers under the same conditions. The degradation rate of methyl orange by AgBr/TiO₂ nanofibers is about 96%.

Up-Conversion Luminescence Property of Er³⁺ Doped and Er³⁺/Yb³⁺ Co-Doped NBT-CT Lead-Free Piezoelectric Ceramics

MA Chunlin, ZHOU Yue, MA Chenyu, DONG Qianwen, WU Jin, FAN Yuxiang, ZHAI Zhangyin

2021, 50(1):  138-143. 

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A series of Er³⁺ doped and Er³⁺/Yb³⁺ co-doped 0.96Na_0.5Bi_0.5TiO₃-0.04CaTiO₃(NBT-CT∶xEr³⁺/yYb³⁺,x=0.002~0.015, y=0.010) lead-free piezoelectric ceramics were prepared by a solid-state sintering method. The phase structure and up-conversion luminescence properties of the samples were characterized and analyzed by X-ray diffraction and fluorescence spectrofluorometer, respectively. These results show that the main crystal phase of the samples is that of NBT. Under the excitation of a 980 nm near-infrared light, the Er³⁺ doped and Er³⁺/Yb³⁺ co-doped NBT-CT ceramics exhibit characteristic emission of Er³⁺ with strong dominant green up-conversion emissions. The optimal up-conversion luminescence performance with x=0.010 in NBT-CT∶xEr³⁺ ceramics are obtained. Yb³⁺ can act as sensitizer and significantly enhance the up-conversion luminescence intensity of Er³⁺.

Effect of Nano-Yb₂O₃ on Crystallization Kinetics Mechanism of Fused Quartz

GU Yinglei, YAN Yaxi, BU Jinglong, MA Chao, WANG Zhifa

2021, 50(1):  144-150. 

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The effect of nano-Yb₂O₃ on the crystallization mechanism and kinetics of fused quartz were studied. The effect of nano-Yb₂O₃ on crystallization ratio of fused quartz ceramics was studied by means of XRD, and the effect of nano-Yb₂O₃ on the crystallization mechanism of fused quartz ceramics was studied by kinetic method, meanwhile, the isothermal crystallization kinetics of two kinds of fused quartz ceramics were discussed. The results show that the grain growth mode of fused quartz ceramics is two-dimensional growth accompanied by one-dimensional and three-dimensional growth, while the grain growth mode of fused quartz ceramics with nano-Yb₂O₃ is two-dimensional accompanied by three-dimensional growth. The activation energy E of samples B and samples Y are 874 kJ/mol and 1 188 kJ/mol, respectively. With the introduction of nano-Yb₂O₃ in fused quartz ceramics, the "active nucleation point" of SiO₂ glass for cristobalite reduce greatly, the stability of the glass surface structure increases, the crystallization activation energy increases, and the crystallization ratio of fused quartz reduces greatly.

Reviews

Progress and Application on the Measurement Technique of Single Crystal Silicon Lattice Spacing

LI Wei, SHI Yushu, LI Qi, HUANG Lu, LI Shi, GAO Sitian

2021, 50(1):  151-157. 

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Lattice spacing of single crystal silicon is the fundamental of measurement of some physical constants. In this paper, the progress of the silicon lattice spacing measurement technique is introduced, including X-ray interferometer for direct measurement and lattice comparator for indirect measurement, and the key factor affecting the uncertainty of lattice spacing measurement are discussed. Due to the development of silicon lattice spacing measurement, the Si lattice spacing is used as a secondary realization of the definition of the metre at nanoscale, approved by BIPM. At last, the application of lattice measurement in metrology and research trends of the traceability system for nano dimension metrology based on the lattice are introduced.

Review for Frequent Characteristics of Diamond UV-Vis-MIR Spectra

LI Jianjun, FAN Chengxing, CHENG Youfa, LIU Xuesong, WANG Yue, SHAN Guangqi, LI Ting, LI Guihua, DING Xiuyun, ZHAO Xiaoxue, HUANG Zhun, YAN Fei, DU Ran

2021, 50(1):  158-166. 

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The “type” of diamond had been developed and trended to perfect in last century. The spectral classification depends on ultraviolet visible near infrared spectrum (UV-Vis-NIR) and mid-infrared spectrum (MIR), mainly relates to nitrogen and boron impurity element. The structure models of nitrogen and boron in each type of diamond have tended to be more plausibility, but an enormous number of lattice defects even related to nitrogen are huge challenge for future work to reach a better understanding. This is an impenetrable wall on the way to explore new application areas for diamond. This article compiles some absorption characteristics in the spectra ranged from ultraviolet, visible light to infrared region. Especially the diamond classification system has been summarized completely. Furthermore, some absorbing features detected in the ultraviolet-visible and infrared spectral lines (UV-Vis-MIR) have been come up with a plausible explanation and/or established somewhat more reasonable structure models. It is very referential collecting these spectral characteristics and their corresponding theoretical models for further research and apply diamond materials.

Recent Research Progress on Tungsten and Molybdate Red Luminescent Material for White LED

RUAN Wenke, XIE Mubiao

2021, 50(1):  167-178. 

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The performance of red luminescent materials has an extremely important influence on the color rendering index and color temperature of white LEDs. This article mainly introduces the structural composition, luminescence properties and research results of several major systems of red luminescent materials such as scheelite type tungsten/molybdate, double perovskite type tungsten/molybdate and composite tungsten/molybdate, the future prospects of tungsten/molybdate red luminescent materials is prospected.

Preparation of Micro-Nano Structure Based on Laser Induced Forward Transfer Technique

SHEN Huijuan, WENG Zhankun, CHEN Xingyuan, DENG Liqiang, HAN Taikun, QI Lingmin, LAI Guoxia, NING Turong, MA Lizheng

2021, 50(1):  179-186. 

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Laser direct writing(LDW) technology is one of the popular technologies in digital micro-nano machining, in which ink-jet printing technology has been widely used for its high resolution and flexibility. With more appearance of the functional materials and application requirements, the strict choice of ink-jet printing technology to the ink limits its application in some fields. Laser-induced forward transfer (LIFT) technology does not require templates and nozzles. The micro- and nano- structure printed by LIFT has high resolution, and will not be limited by the rheological properties of ink. It is appropriate to print various materials with nearly all the solids and liquids, and has be widely used in electronics, sensors, and tissue engineering in regenerative medicine. In this paper, the research progress of the LIFT has been reviewed, the physical process and application of LIFT technology have been summarizes, which will provide the reference for the further research of LIFT technology in the field of micro-nano machining.

Research Progress on Rare-Earth Perovskite Oxynitrides

YE Shiya, LI Duan, LI Junsheng, ZENG Liang, CAO Feng

2021, 50(1):  187-198. 

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In recent years, rare-earth perovskite oxynitrides have attracted much attention due to their excellent multifunctionality and their application prospects in the fields of optical, photocatalytic, dielectric and magnetic materials. The calculation method for structure stability of rare-earth perovskite oxynitrides is introduced, and the synthesis methods are summarized. At last, this paper states main application and makes prospects for future research priorities in this field.

Research Progress on Phase Transition Mechanism and Preparation Technology of α-Al₂O₃

WU Yufeng, ZHANG Tiejun, ZHANG Jiameng, BI Zuozhen, LEI Ming, BI Ke

2021, 50(1):  199-208. 

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α-Al₂O₃ has important applications in refractories, electronic materials and many other fields. This article first introduces the evaluation index of α-Al₂O₃ in industrial application and α-Al₂O₃ phase transition mechanism. Then the article expounds related research progress of the α-Al₂O₃ preparation, from three aspects that solid phase synthesis, liquid phase synthesis and gas phase synthesis, respectively. The factors which affect the microstructure of α-Al₂O₃ particles during preparation are discussed, including calcination temperature, mineralizer, pH value and pretreatment conditions. Finally, the lack of research on the nucleation growth mechanism of α-Al₂O₃ is pointed out, and indicating that a specific nucleation mechanism, the mass production of high purity α-Al₂O₃ and morphology control technology will be the future research focus and development direction in this field.