Table of Content

15 April 2023, Volume 52 Issue 4

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Research Letter

Growth of High Quality ø10 Inch Yb:YAG Laser Crystal by Czochralski Method

LI Xingwang, YANG Guoli, HAN Jianfeng, WANG Yongguo, BI Hai, XU Xuezhen

2023, 52(4):  547-549. 

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The thermal field of growing Yb:YAG laser crystal with a diameter of 10 inch has been designed and fabricated, and the structure of single crystal growth furnace has been improved. The Yb:YAG crystal with a diameter of 252 mm and a cylinder length of nearly 260 mm has been successfully grown by induction heating Czochralski method combined with automatic diameter control system. There is no visible crack and scattering particle under the irradiation of 5 mW green laser and 20 mW He-Ne laser in the boule. The optical uniformity and stress of the boule was inspected after polishing. The results show that the available sectors of this boule have good optical uniformity and uniform stress distribution. A crystal slab with size of 152 mm×11.5 mm×260 mm can be selected in one available sector of this boule, and its transmitted wavefront distortion is 0.29λ/inch@633 nm.

Research Articles

Modeling and Numerical Simulation of Heat-Mass Transport Process for Large-Size Silicon Carbide Crystal Growth

LU Jiazheng, ZHANG Hui, ZHENG Lili, MA Yuan

2023, 52(4):  550-561. 

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The functionality and performance of the electronic product are heavily dependent on its quality of power device and radio frequency device, thus further determined by the quality of SiC substrate. Hence, the manufacturing of superior SiC single crystal is of significant importance. One popular way of growing large-diameter SiC single crystal is to leverage physical vapor transport (PVT) method. However, this method admits a common challenge in thermal design and flow control. To tackle this problem, a numerical simulation study of the complete process of growing 150 mm SiC single crystal by resistive heating PVT method was proposed in this paper. A mathematical model to capture the growing process, which comprises the pyrolysis and recrystallization of source materials, the porous structure evolution, the heat-mass transport in the system, and the morphology changes of crystal growth front was established. In order to validate our developed model, the numerical simulations were implemented to study the interaction among the crystal growth, the consumption of source materials, and the thermal field changes. The results show that the high temperature on the side of the source area leads to uneven gas flow, and the high temperature at the bottom results in a uniform airflow and a slightly convex crystal surface. Meanwhile, the growth interface adjusts the equilibrium pressure of the gas species through the radial temperature distribution, therefore, the crystal surface grows into an isotherm shape. In addition, the crystal growth rate is positively correlated with the temperature of the source area and the amount of remaining raw materials. The simulation results are consistent with the reported experimental results inherently, which lay a solid foundation for the optimal growth of large-scale and high-quality SiC single crystals.

Effect of High Pulling Rate on the Distribution of Point Defects and Energy Consumption in ø 300 mm Monocrystalline Silicon

XU Zunhao, LI Jin, HE Xian, AN Baijun, ZHOU Chunling

2023, 52(4):  562-570. 

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The “efficiency and cost reduction” of large size Czochralski monocrystalline silicon is an urgent problem for photovoltaic enterprises. In this paper, the finite element volume method was used to simulate the growth process of ø300 mm Czochralski monocrystalline silicon in both steady and unsteady state, respectively, to study the change rule of crystal-melt interface, point defect distribution and growth energy consumption during the growth process of Czochralski monocrystalline silicon by increasing the pulling rate. The results show that the shift of crystal-melt interface is 33 mm when the pulling rate increases to 1.6 mm/min, which would not affect the stable growth of crystals. The pulling rate plays a decisive role in the distribution of point defects in the crystal. Increaseing the pulling rate could not only reduce the concentration of self-interstital defects, but also make the V/G in the crystal bar always higher than the critical value. And the pulling rate has a great influence on the power consumption. After increasing the pulling rate, the crystal growth time is reduced by 46.4%, and the power consumption for monocrystalline silicon growth is reduced by 4.97%. Optimization and control of appropriate pulling rate is conducive to low cost growth of specific point defect distribution or even point defect free monocrystalline silicon, which provides some theoretical support for improving the quality of large size Czochralski monocrystalline silicon and reducing production energy consumption.

Effect of Trace La Impurities on the Spectral Properties of CaF₂ Crystals with γ-Irradiation Induced Color Centers

WANG Donghao, KOU Huamin, SHAO Chongyun, JIANG Dapeng, ZHANG Bo, WANG Jingya, QIAN Xiaobo, ZHANG Zhonghan, WU Qinghui, SU Liangbi

2023, 52(4):  571-577. 

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The resistance of calcium fluoride crystals to γ-irradiation is one of the key properties for its application in space. In this paper, the effect of trace La impurities on the γ-irradiation induced color center of calcium fluoride crystals was reported. The calcium fluoride crystals with trace La impurities were studied by absorption spectroscopy and electron paramagnetic resonance (EPR). The results show that the irradiated calcium fluoride crystals produce multiple color center absorption bands, and the absorption band increases with the increase of irradiation dose and the concentration of La impurities. EPR confirms that the formation of this absorption band is caused by the F color center in the calcium fluoride crystal. The presence of La³⁺ affect the stability and spectral position of the F centers in calcium fluoride crystals. Possible mechanisms for the presence of La³⁺ and F centers in calcium fluoride crystals are proposed.

Growth and Luminescence Properties of 1 Inch CsPbCl₃ Crystals

WANG Qing, WU Shufan, LU Zhichen, QIAN Lu, PAN Shangke, PAN Jianguo

2023, 52(4):  578-583. 

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CsPbX₃(X=Cl^-, Br^-, I^-) pervoskite single crystals have excellent photoelectric properties, and are promising to become the next generation of photoelectric detection materials. It is difficult to grow CsPbCl₃ crystals by low-temperature solution method due to the solubility of CsCl in the precursor is too small. Here, 1 inch complete CsPbCl₃ crystals were grown by Bridgman method, a series of processing was performed on the crystals to obtain single crystal sheets of ø10 mm×10 mm and 2 mm thickness. X-ray powder diffraction patterns, TG/DTA curves, X-ray excitation emission spectra, transmission spectra and low temperature fluorescence spectra of the crystals were measured. Under X-ray excitation, two X-ray excitation peaks are observed at 430 and 575 nm, and the transmittance of the crystal reaches 75%; thermal quenching could be observed by the photoluminescence (PL) intensity versus temperature dependence curve, and the exciton binding energies of the four peaks of the crystal are calculated to be 12.59, 8.21, 12.41 and 21.59 meV, respectively.

Scintillation Properties and Irradiation Damage of Large Size BaF₂:Y Scintillation Crystals Grown by Bridgman Method

HOU Yueyun, LIU Jianqiang, YANG Lei, YAN Jinli, ZHANG Mingrong, LIU Xiaoyang

2023, 52(4):  584-589. 

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The 40 mm×40 mm×350 mm BaF₂:5%Y (mole fraction) crystals were grown by vertical Bridgman method. The doping content, scintillation properties, optical properties and irradiation damage of crystal samples were studied. The Y³⁺doping concentration (mole fraction) is 5.1%±0.9% within the range from 0 to 300 mm from seed end. The average light output of crystal sample is 2 100 ph/MeV, and the optimal energy resolution at 662 keV is 10.1%. After ⁶⁰Co source was used to irradiate the sample with an accumulated dose of 1 Mrad, the transmittance of the sample at 220 nm wavelength decreases from 87.3% before irradiation to 83.5%, the transmittance at 300 nm wavelength decreases from 91.8% to 89.9%. The anti-irradiation performance of BaF₂:Y crystal is worse than that of BaF₂ crystal. After the accumulative dose irradiation, the absorption of BaF₂:Y crystal to 300 nm light is significantly enhanced.

Bandgaps of a Helmholtz-Type Phononic Crystal with Adjustable Chamber

LIU Hong, ZHAO Jingbo, YAO Hong, HAN Donghai, ZHANG Xiaosheng, WANG Chen, ZHANG Guangjun

2023, 52(4):  590-597. 

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For low-frequency noise control problems, a Helmholtz-type phononic crystal with an adjustable chamber was constructed. The inner chamber of the structure is divided into upper and lower chambers by a diaphragm connected by a movable telescopic screw. Meanwhile, an arch-shaped opening channel is adopted. Characteristics of bandgap and sound insulation of the structure are analyzed by finite element method, and equivalent models of the structure at the starting frequency and cut-off frequency of the bandgap are constructed by “acoustic-force analogy” method. The results show that the designed structure can generate six complete bandgaps within 500 Hz, and the lowest bandgap frequency can reach 31.34 Hz. At the same time, it shows good sound insulation performance in each bandgap frequency band, and the maximum sound insulation is up to 111.95 dB. Finally, by adjusting the telescopic screw and changing the cavity structure layout, multiple resonant bandgaps can be connected to form a wide bandgap, and achieve the purpose of adjusting the sound insulation band. This design provides a new idea for the sound insulation performance of Helmholtz type phononic crystals.

Synthesis, Crystal Structure and Magnetic Property of a Terbium Cluster

WANG Qi, ZHU Xiaoming, WANG Juntao, LI Zeyu, JI Liudi, HU Peng

2023, 52(4):  598-603. 

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In this paper, a new nonanuclear terbium cluster {Tb₉(L)₄(μ₄-OH)₂(μ₃-OH)₈(μ₂-OCH₃)₄ (NO₃)₈(H₂O)₈}(OH)·2H₂O(1) was synthesized by 2,6-dimethoxyphenol (HL) and Tb(NO₃)₂·6H₂O. The cluster was characterized via XRD, elemental analysis, infrared spectrum and thermogravimetric analysis. The magnetic property were also studied. X-ray single-crystal diffraction analysis indicates that the cluster is orthorhombic, the space group is I222, the crystal cell parameters are a=1.532 8(3) nm, b=1.796 9(4) nm, c=1.863 5(4) nm, α=β=γ=90°, V=5.132 6(19) nm³. The nonanuclear skeleton formed by metal centers in the cluster that connected by μ₄-OH and μ₃-OH presents an interesting hourglass like topology. The central Tb ion has a slightly twisted tetragonal pyramid geometry, while the other Tb ions have a slightly deformed dodecahedral configuration. Magnetic investigations reveal that the weak antiferromagnetic interactions between adjacent metal ions exist in cluster 1, but no obvious slow magnetic relaxation behavior is shown due to the rapid magnetic quantum tunneling effect.

Preparation and Up-Conversion Luminescent Properties of Mn²⁺ Doped Gd₂O₃:Yb³⁺, Er³⁺ Flower-Like Microcrystals

WANG Chao, CHEN Jie, YIN Yu, LIU Rong, WANG Shanshan, LIU Zhigang

2023, 52(4):  604-612. 

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In order to obtain up-conversion luminescent materials with bright red emission, a series of Yb³⁺, Er³⁺, Mn²⁺-doped Gd₂O₃ microcrystals were prepared by simple chemical precipitation method, and their morphology, structure and luminescent properties were characterized. The results show that Gd₂O₃:10%Yb³⁺,1%Er³⁺ microcrystals exhibit a flower-like morphology, and the average diameter is 2.28 μm. After calcination at high temperature, the sample presents a cubic Gd₂O₃ structure with good crystallinity, and Mn²⁺ doping does not affect the morphology and crystal phase of the product. Under 980 nm near-infrared light excitation, Gd₂O₃:10%Yb³⁺,1%Er³⁺ microcrystals show orange-red luminescence, which corresponds to the ⁴F_9/2→⁴I_15/2 transition of Er³⁺. With the increase of Mn²⁺ doping concentration (molar fraction), the luminescence intensity of Gd₂O₃:10%Yb³⁺,1%Er³⁺, x%Mn²⁺ microcrystals first increases and then decreases, and the luminescence color gradually turns to red, which is consistent with the CIE color coordinate. At the same time, the up-conversion luminescence mechanism and the possible energy transfer process of Gd₂O₃:10%Yb³⁺,1%Er³⁺, x%Mn²⁺ microcrystals were analyzed according to the relationship between luminescence intensity and excitation power.

Electronic and Piezoelectric Properties of Two-Dimensional Janus Chromium Dichalcogenides

GE Chang, ZHOU Guoxiang, QIN Xuchen, WANG Guang, YAN Tongtong, LI Jia

2023, 52(4):  613-620. 

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In this paper, the electronic and piezoelectric properties of two-dimensional Janus CrXY (X/Y=S, Se,Te) systems were investigated. The results show that the Janus CrXY systems are excellent semiconductor materials and the band gap widths of Janus CrXY range from 0.27 eV to 0.83 eV. The strain regulation in the x-axis direction has a great influence on the band gap, while the strain regulation in the z-axis direction has little influence on the band gap, indicating that the electronic properties of the system have good stability in the z-axis direction. The piezoelectric properties of the system were studied by density generalized perturbation method, the results show that all three materials have large out-of-plane piezoelectric coefficients d₃₃, especially, the d₃₃ of CrSeTe reaches 56.89 pm/V, which is about ten times that of the common piezoelectric material AlN (d₃₃=5.60 pm/V). This research provides theoretical support for the practical application of two-dimensional Janus CrXY systems in the field of flexible and intelligent nanomaterials.

Effect of Zinc Doping on the Structure and Multiferroic Properties of Bismuth Ferrite Thin Films

YANG Song, HE Yingzi, WANG Jianwei, ZHANG Min, WANG Xu

2023, 52(4):  621-628. 

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BiFe_1-xZn_xO₃ (BFZO) (x=0, 2%, 4%, 6%) thin films were successfully prepared on Pt/Ti/SiO₂/Si substrates by sol-gel method. The effect of Zn doping on the structure, surface morphology, leakage current density, ferroelectric and ferromagnetic properties of BiFeO₃ (BFO) thin films were investigated systematically. XRD patterns show that all samples match well with the perovskite structure without impurity phase. SEM images show that BFZO thin films with x=4% exhibit uniform fine grains and higher density, which is instrumental for the improvement of leakage current density. The leakage current density curve shows that BiFe_0.96Zn_0.04O₃ thin films have the lowest leakage current density (J=1.56×10^-6 A/cm²) under the electric field strength of 300 kV/cm, which is three orders of magnitude lower than that of pure BFO thin films. Furthermore, BiFe_0.96Zn_0.04O₃ thin film exhibits the largest remnant polarization (2P_r=20.91 μC/cm²) at room temperature, which is more than four times as large as that of pure BFO (2P_r=4.96 μC/cm²). Additionally, compared with BFO thin film, Zn doping also enhances the ferromagnetic properties of BFO thin films, and as Zn doping concentration increases, the saturation magnetization of BFZO thin films is significantly enhanced, which provides potential applications in information storage.

Growth and Properties of Tl-1223 High Temperature Superconducting Films on Sapphire Single Crystal Substrates

HAN Xu, JIN Yanying, ZENG Li, YUE Hongwei, JIANG Yanling, TANG Pingying, HUANG Guohua, XIE Qinglian

2023, 52(4):  629-635. 

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In this paper, the R-cut sapphire single crystal substrates were selected, and the CeO₂ buffer layers were grown on the surfaces of substrates by RF magnetron sputtering method, then the high quality Tl-1223 superconducting films were grown by the rapid heating-up sintering technology. The effects of buffer layer growth and post annealing conditions of the precursor films on the crystallization and superconducting properties of the superconducting thin films were studied. AFM and XRD measurements show that the surface of sapphire substrates have a step structure with smooth platform and the crystal quality of sapphire substrates have been improved after annealing; the CeO₂ buffer layers and the Tl-1223 superconducting films all have good c-axis growth orientation under appropriate parameters, and they exist a good ab-plane texture. SEM measurements show that the well grown Tl-1223 superconducting films have a layered structure and their surfaces are dense and smooth. The T_c of the prepared superconducting film is measured to be about 111 K, and J_c (77 K, 0 T) is measured to be about 1.3 MA/cm² in liquid nitrogen environment.

Optimization of Antimony Selenide Thin Film Solar Cells Performance Based on Cesium Chloride Back Contact Treatment

ZHAO Cong, GUO Huafei, QIU Jianhua, DING Jianning, YUAN Ningyi

2023, 52(4):  636-644. 

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Antimony selenide (Sb₂Se₃) thin film solar cells were prepared by vapor transport deposition, and cesium chloride (CsCl) solution was used to treat the upper interface of the device. Meanwhile, a series of characterizations of the thin film and the device were also performed. The study shows that the back contact treatment of CsCl solution can not only improve the carrier collection and reduce upper interface recombination of the device, but also optimize the crystallinity, surface roughness and optoelectronic performance of thin film. Based on the device structure of FTO/CdS/Sb₂Se₃/CsCl/Au, a high-efficiency Sb₂Se₃ thin film solar cell with efficiency of 6.32% are obtained, which is 12% higher than that of the basic device. The research may provide some guidance to further development of Sb₂Se₃ thin film solar cells and other similar types of semiconductor photovoltaic devices.

Ni₂P@2D Phosphorene Bifunctional Electrocatalyst for Photovoltaic Assisted Overall Water Splitting to Hydrogen Evolution

WANG Juan, LIANG Junhui, FAN Haoyang, LIU Hongming, CHEN Da, CHEN Huayu, HUANG Yuexiang, QIN Laishun

2023, 52(4):  645-653. 

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Recently, two-dimensional phosphorene (2D BP) has become an ideal material for electrocatalysts due to its short charge transport distance, high carrier mobility and fully exposed surface active sites. However, the inadequate adsorption energy of oxygen-containing intermediates results in the sluggish reaction kinetics, and thus limits its practical application. In this paper, granular amorphous Ni₂P on the surface of BP to construct Ni₂P@BP heterostructure were introduced, in order to improve its electrochemical stability and reaction activity. The results show that, compared with the pure BP and Ni₂P catalysts, the Ni₂P@BP catalyst exhibits excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic activities with an overpotential of 167 and 186 mV at a current density of 10 mA/cm², respectively. As a bifunctional electrocatalyst, Ni₂P@BP requires only 1.54 V applied bias (V_app) to achieve a current density of 10 mA/cm². Finally, over 7% solar to hydrogen (STH) coversion efficiency is achieved assisting with a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cell, which is 95% higher than that of pure BP as a bifunctional electrocatalyst.

Preparation of Pt/Co-N-C Electrocatalytic Material and Its ORR Performances in Alkaline Electrolyte

REN Zhili, DUAN Lei, XU Shoudong, CHEN Liang, YI Qun, ZHANG Ding

2023, 52(4):  654-662. 

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Metal-organic frameworks (MOFs) are regarded as effective precursors for the preparation of M-N-C oxygen reduction electrocatalytic materials. However, the structural collapse of MOFs during the pyrolysis limits their practical application. In this study, ZIF-67 was firstly modified by coating with the surfactant of F-127 and doping with Zn. After that, the modified Zn-ZIF-67@F-127 was pyrolyzed under argon atmosphere to fabricate the Co-N-C support with complete structure. By loading Pt on the surface of Co-N-C support, the Pt/Co-N-C composite catalyst for oxygen reduction reaction (ORR) was obtained. The ORR catalytic performances in the alkaline electrolyte were systematically studied. The experimental results show that the addition of F-127 can improve the morphological retention of Zn-ZIF-67@F-127 during the pyrolysis. More importantly, the onset potential, half-wave potential, and diffusion-limited current density of Pt/Co-N-C in O₂-saturated 0.1 mol·L^-1 KOH are 1.027 V, 0.836 V, and 5.51 mA·cm^-2, respectively, which are similar to those of the commercial 20% Pt/C catalyst. The synergistic effect of Pt and Co-N-C not only exhibits a high selectivity and current density for the ORR four-electron pathway, but also shows a high stability approaching the commercial 20% Pt/C catalyst, and superior methanol resistance performance compared with the commercial 20% Pt/C in the chronoamperometry test.

Preparation and Electrochemical Performance of Molybdenum Disulfide Nanosheets for Supercapacitor

ZHANG Rui, WANG Youqi, SHEN Peizhi

2023, 52(4):  663-670. 

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Nanosheet molybdenum disulfide (MoS₂) electrode materials for supercapacitor were prepared by high-temperature solid-phase method combined with ball milling using sodium molybdate and thiourea in a Mo to S molar ratio of 1:15 as raw materials. The thermal stability, phase structure and microstructure were characterized by thermogravimetric-differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. The eletrochemical properties of the samples were tested by cyclic voltammetry (CV), galvanostatic charge/discharge cycling (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the number of MoS₂ layers prepared by sintering at 750 ℃ and ball milling at 700 r·min^-1 for 10 h is 88. The specific capacitances of the samples are 82.4 and 60.9 F·g^-1 at the current density of 0.5 and 1 A·g^-1, respectively (better than 54.6 and 24.0 F·g^-1 before ball milling). After 2 000 cycles, the specific capacitance retention rate is 92%.

Reviews

Research Progress of Rare Earth Halide Scintillation Crystals for Neutron/Gamma Dual Detection

WANG Xiaoli, YANG Lei, HOU Yueyun

2023, 52(4):  671-677. 

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In recent years, with the further study of rare earth halide scintillation crystals, many excellent properties of these materials have been discovered, especially the neutron/gamma ray dual detection performance, which has attracted much attention. Ce doped lithium based elpasolite scintillation crystal with chemical composition of A₂LiRX₆:Ce (A, R, X represent +1 valence metal element, rare earth element, halogen element respectively) and Eu doped lithium based alkaline earth metal halide with chemical composition of LiM₂X₅:Eu (M, X represent +2 valence metal element, halogen element respectively) are considered to be very practical and potential dual detection materials. They can detect neutrons and gamma rays simultaneously, and most of them have high light output, excellent energy resolution and other characteristics. At present, as the most representative of Ce doped lithium based elpasolite scintillation crystal, Cs₂LiYCl₆:Ce (CLYC) has been widely studied and produced. However, Eu doped lithium based alkaline earth metal halide, which is expected to replace elpasolite scintillation crystal materials such as CLYC, is rarely reported. In this paper, the research progress of the above two kinds of dual-mode detection materials is briefly reviewed, with a view to enlightening researchers in related fields.

Research Progress of Metal Phthalocyanine Crystals Synthesized by Solvothermal Method

LI Dapeng, SUN Guofu, GE Suxiang

2023, 52(4):  678-687. 

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Metal phthalocyanine is a class of synthetic planar macrocyclic complex with isoindoles as component unit. They are not only used as high-quality pigments or dyes, but also as novel materials in the fields of solar cells, liquid crystal materials, information storage, environmental catalysis and so on. For traditional preparation of metal phthalocyanine, the reflux reactions with high boiling point solvent were often required and the concentrated sulfuric acid was also used to purify the products. Therefore, the obvious disadvantages of these traditional methods are low efficiency and environmentally unfriendly for their dependence on the high toxicity solvents. From the perspective of the development of green chemistry and preparation requirements of novel metal phthalocyanine materials, the future development trend of metal phthalocyanine synthesis is the one via green processes with the characteristics of environmentally friendly, low cost and facile purification. The research progress of metal phthalocyanine crystals synthesized by one-step solvothermal method were reviewed, and their experimental conditions, and product structures were summarized in detail. Besides, the advantages of this method were evaluated. The future development of metal phthalocyanine crystals synthesized by solvothermal method was predicted.

Preparation of BaTiO₃ Thin Film and Its Application in Electro-Optic Modulator

REN Yijing, MA Xinguo, ZHANG Feng, LU Jingjing, ZHANG Li, WANG Han

2023, 52(4):  688-700. 

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BaTiO₃ has become the key materials for the preparation of high-performance electro-optical modulators due to its high electro-optical coefficient, excellent piezoelectric properties and nonlinear optical properties. The quality, growth orientation and electro-optic coefficient of the film are determined by the preparation method, experimental condition and the selection of substrate, and further affecting the propagation loss, half-wave voltage and extinction ratio of the electro-optical modulator. Based on the working principle of electro-optical modulator, the factors affecting the orientation and quality of film forming were discussed by focusing on the preparation methods, experimental conditions and film substrates of BaTiO₃ thin film in this paper. The advantages and disadvantages of each process of BaTiO₃ thin film preparation were analyzed, the structure and performance of waveguide were discussed. Finally, the direction of optimizing BaTiO₃ thin film fabrication and waveguide fabrication process in the future were summarized in this paper.

Research Progress of SnS₂-Based Gas Sensing Materials

LI Shaojun, YAO Yue, CHEN Junming

2023, 52(4):  701-709. 

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Gas sensors can effectively detect toxic, harmful, flammable and explosive gases with concentrations below the human olfactory limit, and have great research significance in the fields of military defense, environmental safety, medical diagnosis and so on. Among them, resistance gas sensor is widely used because of its low cost and universal suitability for civil gas detection. Gas sensing material is the core of gas sensor, and it is very important to design and synthesize suitable gas sensing material for developing high performance gas sensor.Based on the brief introduction of gas sensor, resistive gas sensor, and several traditional gas sensing materials of resistive gas sensor, this review focuses on the SnS₂ gas sensing materials, a class of n-type semiconductors. The structure, properties, research status and limitations of SnS₂ gas sensing materials are summarized. Several important methods to improve the performance of SnS₂ gas sensing materials and SnS₂-based gas sensors are summarized, including vacancy engineering, thermal activation engineering, photoactivation engineering and heterojunction engineering. The research trend of SnS₂-based gas sensors is prospected.

Progress on Controllable Preparation of Polycrystalline and Polymorphic Nano Calcium Carbonate by Calcium Carbide Slag

DING Yu, ZHANG Jincai, WANG Baofeng, GUO Yanxia, XUE Fangbin, CHENG Fangqin

2023, 52(4):  710-720. 

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Calcium carbonate has different crystal characteristics, which makes it play different roles in various application fields. The control of calcium carbonate crystal structure, morphology and size is a hot research topic in the preparation of inorganic materials. The preparation of nano calcium carbonate produced from calcium carbide slag can realize the transformation of waste into resource, which is one of the important research fields concerning the recycling of calcium-containing solid wastes. The controllable preparation of calcium carbonate with different crystalline structure and morphology from calcium carbide slag can make the worthless calcium carbide slag transform into high value-added nano grade products with good environmental and economic effects. The preparation methods of nano calcium carbonate from calcium carbide slag are summarized in this paper, the research progress of the control of crystal structure and morphology during the preparation process is discussed emphatically. The results indicate that, during the nucleation and growth of calcium carbonate crystals, controlling the process conditions can further achieve the regulation of crystal structure and morphology by influencing the degree of supersaturation, and the action mechanism varies from different kinds of additives. As the basis for controlling the equilibrium of the crystallization processes, thermodynamics and kinetics can be used to explain the mechanism of action of each influencing factor.