Table of Content

15 May 2021, Volume 50 Issue 5

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Invited

Multifunctional Properties and Device Applications of the Relaxor Ferroelectric Single Crystals

LUO Haosu, JIAO Jie, CHEN Rui, ZHU Rongfeng, ZHANG Zhang, XU Jialin, ZHAO Jing, WANG Xi'an, LIN Di, CHEN Jianwei, DI Wenning, LU Li, ZHU Lili

2021, 50(5):  783-802. 

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The relaxor ferroelectric single crystals, such as Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT or PMNT), exhibit excellent piezoelectric performances, which are much higher than the conventional lead zirconate titanate Pb(Zr_xTi_1-x)O₃ (PZT) ceramics. The ultrahigh piezoelectric performances of the PMN-PT relaxor ferroelectric single crystals induce the research upsurge of the next generation of piezoelectric devices such as ultrasonic transducers. Our research team was the first time to use the Bridgman method to grow the large size and high quality PMN-PT relaxor ferroelectric single crystals (d₃₃~2 000 pC/N, k₃₃~92%) in the world. The growth, hierarchical structure and properties of the PMN-PT relaxor ferroelectric single crystals were systematically and deeply studied in our research team in the past 20 years. Different from the traditional perovskite ferroelectric materials, the PMN-PT relaxor ferroelectric single crystals have hierarchical microstructures, including monoclinic phase structure (M_A, M_B, M_C), domain configuration, nano-regions (PNRs), polarization rotation, resulting in the related research on the origin of ferroelectric materials with high piezoelectricity and the development of the fundamental theory on the ferroelectric physics. It was also found that the PMN-PT crystals exhibit outstanding pyroelectric properties, electro-optic (EO) properties and super high magnetoelectric coupling properties in the magnetoelectric composites composed with the magnetostrictive materials. Based on this, our team is also striving to promote the applications of relaxor ferroelectric single crystals on medical ultrasonic transducers, pyroelectric infrared (PIR) detectors, EO devices, magnetoelectric weak magnetic sensors and other devices. The research results of multifunctional properties and device application of the relaxor ferroelectric single crystals in our team about 20 years are summarized in this paper.

Research Articles

Optical and Scintillation Properties of Cs₂HfCl₆ and Cs₂HfCl₆∶Tl Single Crystals Grown by the Bridgman Method

CHENG Shuangliang, REN Guohao, WU Yuntao

2021, 50(5):  803-808. 

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The ø7 mm undoped Cs₂HfCl₆ and Cs₂HfCl₆∶0.2%Tl(mole fraction) single crystals were grown by the Vertical Bridgman method. The phase, impurities concentrations, luminescence and scintillation properties of crystal samples were studied. Both crystalsbelong to the cubic crystal structure and the space group of Fm3m. When excited by ultraviolet light and X-ray, both crystals exhibit an emission peak at 380 nm originated from self-trapped excitons emission, and Cs₂HfCl₆∶0.2%Tl crystal exhibits an extra Tl⁺ sp-s² transition induced emission at 505 nm. Cs₂HfCl₆ and Cs₂HfCl₆∶0.2%Tl possess high light yields of 37 000 photons/MeV and 36 500 photons/MeV respectively and both have excellent energy resolutions of 3.5% at 662 keV under excitation of ¹³⁷Cs source. The scintillation decay time of undoped Cs₂HfCl₆ is comprised of 0.37 μs (4.2%), 4.27 μs (78.9%) and 12.52 μs (16.9%). The scintillation decay time of Cs₂HfCl₆∶0.2%Tl is comprised of 0.33 μs (3.5%), 4.09 μs (81.9%) and 10.42 μs (14.5%).

Effect of Barrier Temperature on Internal Quantum Efficiency in InGaN Quantum Dots/Quantum Well Hybrid Structure

PING Chen, JIA Zhigang, DONG Hailiang, ZHANG Aiqin, XU Bingshe

2021, 50(5):  809-815. 

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Three InGaN/GaN quantum wells: S₁ (830 ℃), S₂ (840 ℃) and S₃ (850 ℃) with different barrier temperatures were grown by metal organic chemical vapor deposition (MOCVD). Due to the formation of high-density V-shaped pits, the perfect quantum well structure was destroyed and transformed into InGaN quantum dots (QDs)/quantum well (QW) hybrid structure. Atomic force microscopy (AFM), high-angle annular dark-field imaging (HAADF) and energy dispersive spectrometer (EDS) were employed to analyze the morphology and related causes of the three samples. The changes of quantum confined Stark effect (QCSE), nonradiative recombination center density and carrier localization effect at different barrier temperatures were analyzed by EPDD-PL(excitation power density dependent photoluminescence) and TD-PL(temperature dependent photoluminescence). The results show that QCSE is weaker at lower barrier temperature, because at lower temperature, the V-shaped pits are deeper, inducing more obvious stress release and lower the residual strain. With the increase of barrier growth temperature, the density of nonradiative recombination centers increase gradually. The internal quantum efficiency (IQE) of S₁, S₂ and S₃ samples decrease with the increase of barrier growth temperature. Finally, it is found that the enhancement of QCSE and the higher density of nonradiative recombination centers are the main factors for the decrease of IQE with the increase of barrier growth temperature.

Effect of Impurities and Defects on the Thermal Conductivity of Single Crystal SiC

QI Zhengchao, XU Tingxiang, LIU Xuechao, WANG Ding

2021, 50(5):  816-824. 

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Currently the investigations on room-temperature thermal conductivity of single crystal SiC and the dependence of thermal conductivity on temperature show some differences. What's more, most researches relating to the thermal conductivity of single crystal SiC concentrate on the crystalline orientation along c-axis <0001> or vertical to c-axis randomly, which can't account for the anisotropy of thermal conductivity for SiC rigorously. In this paper, the effect of impurities and defects on thermal conductivity of single crystal 4H-SiC and 6H-SiC in three accurately different directions were studied. These samples (sized ø12.7 mm×3 mm) along $<1 \overline{1} 00>$, $<11 \overline{2} 0>$, <0001>, respectively cut from a 4H-SiC and 6H-SiC single crystal were characterized by flash method in order to get their thermal diffusion. The thermal conductivity was derived from the product of thermal diffusion and specific heat. Impurities and defects of these samples were characterized by glow discharge mass spectroscope (GDMS) and scanning electron microscope (SEM), respectively. The experimental results indicate that the thermal conductivity of single crystal SiC along $<1 \overline{1} 00>$, $<11 \overline{2} 0>$, <0001> decreases with increasing the temperature, while the thermal conductivity along <0001> is the smallest among all samples. And the thermal conductivity of 6H-SiC is abnormally larger than that of 4H-SiC as a result of many of impurities within 6H-SiC. Therefore, defect has more obvious effect on the thermal conductivity of single crystal than impurity, which is the reason for the anisotropy of thermal conductivity.

First-Principles Study on Electronic Structure and Optical Properties of Nd-Doped Mg₂Si

LI Yangjun, YANG Kun, ZHOU Tingyan, WU Bo

2021, 50(5):  825-830. 

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The energy band structure, density of states and optical properties of undoped Mg₂Si and Nd-doped Mg₂Si were investigated by the first-principles pseudopotential plane wave method based on density functional theory. The results show that after doping Mg₂Si, the band gap of Mg₂Si decreases from 0.290 eV to 0 eV, the conductivity improves. Undoped Mg₂Si begins to have absorption ability when photon energy is greater than 0.9 eV, while Nd-doped Mg₂Si begins to absorb photons with energy of 0.2 eV, the absorption of infrared electrons is improved after doping. The absorption coefficient and reflectivity of doped Mg₂Si decrease, which indicates that the light transmittance of doped Mg₂Si increases. The calculated results provide a theoretical basis for the application of Mg₂Si materials in optoelectronic devices.

Growth Mechanism and Optical Properties of ZrN Films by Magnetron Sputtering

GAO Jie, YAO Weizhen, YANG Shaoyan, WEI Jie, LI Chengming, WEI Hongyuan

2021, 50(5):  831-837. 

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In this work, zirconium nitride (ZrN) films with high crystalline quality were deposited on Si (111) substrates by direct current magnetron reactive sputtering. The effect of deposition time on the structural property, surface morphology and optical property of the ZrN films were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM) and spectroscopic ellipsometry (SE). The results confirm that all the ZrN films have a cubic, NaCl-type crystal structure with (111) single orientation and the crystalline quality of the films increase with the increasing deposition time. The surface morphology, grain size and surface roughness of ZrN films change with deposition time. A dense columnar structure with triangular pyramid-shaped grains is observed when the deposition time increased to 45 min. Subsequently, the growth mechanism of ZrN films was explained using Extend Structure Zone Model. Finally, the reflection characteristics of ZrN films were studied. It is found that the reflectivity decrease when the film has a triangular pyramid texture, compared with that of none texture counterparts. Moreover, with increasing deposition time to 45 min, there are oscillations in the reflectance spectrum with the wavelength range of 300~800 nm, which did not occur in the films with shorter deposition time. The correlations between growth conditions, crystal structure, microstructure as well as optical properties, could provide an important reference value for optimum conditions to produce ZrN films for utilization in devices applications.

Effects of Different Annealing Conditions on the Characteristics of Ga₂O₃ Thin Films Prepared by PEALD

MA Haixin, DING Guangyu, XING Yanhui, HAN Jun, ZHANG Yao, CUI Boyao, LIN Wenkui, YIN Haotian, HUANG Xingjie

2021, 50(5):  838-844. 

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Gallium oxide (Ga₂O₃) thin films were prepared on c-plane sapphire substrates by plasma enhanced atomic layer deposition (PEALD). The effects of annealing atmosphere (v(N₂)∶v(O₂)=1∶1 (volume ratio), Air and N₂) and annealing time on the crystal structure, surface morphology and optical properties of Ga₂O₃ films were studied. The research results indicate that gallium oxide is in metastable state before annealing, and the crystal structure changes significantly after annealing in different annealing atmospheres, and the increase in the proportion of N₂ in annealing atmosphere is beneficial to the recrystallization of Ga₂O₃. Furthermore, the effect of annealing time was further studied under N₂ atmosphere, and the results show that the structure of the thin film changes from metastable state to β-Ga₂O₃ with good single orientation after annealing for 30 min in N₂ atmosphere. And the surface morphology analysis show that the surface morphology begins to stabilize after annealing for 30 min, and the surface grain density no longer increases. In addition, the average transmittance of the sample in the range of 400 nm to 800 nm is almost 100%, and the light absorption edge is steep. Annealing in N₂ atmosphere is more conducive to the migration of atoms on the surface of the film for Ga₂O₃ deposited in an oxygen-rich environment, and Ga₂O₃ recrystallization is preferred.

Influence of Different Annealing Temperatures on the Magnetic Properties of Barium Ferrite Films

ZHANG Weitong, DAI Bo, REN Yong, NI Jing

2021, 50(5):  845-850. 

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M-type barium ferrite (BaFe₁₂O₁₉, BaM) is a kind of uniaxial magnetocrystalline anisotropic hexagonal crystal system hard magnetic material. Because of strong magnetocrystalline anisotropy, it has broad application prospects in the field of self-biased microwave devices. In this paper, the normal temperature RF magnetron sputtering method was used to deposit a BaFe₁₂O₁₉ amorphous film with a thickness of about 130 nm on a sapphire (000l) substrate. Then they were annealed at 850 ℃, 900 ℃, 950 ℃, and 1 000 ℃ for 3 h to obtain BaM crystal film samples. X-ray diffraction method is used to identify the phase and crystal growth orientation of the film sample. The roughness and surface morphology of the film sample are measured and observed using a scanning probe microscope and a scanning electron microscope. X-ray diffraction results show that the main crystal phases of BaM are grown along the (000l) orientation, which is contributed by two factors: (1) suitable RF sputtering power and pressure; (2) BaM and sapphire have the same hexagonal. The crystal structure and the matching degree of unit cell parameters are relatively high, which can induce the crystal grain orientation of the film. When the annealing temperature reaches 950 ℃, the film begins to show the diffraction peaks of non-BaM crystal phase, indicating that excessive annealing temperature will cause the generation of impurity phases. When the annealing temperature is 900 ℃, the surface microstructure shows uniform grain size and clear interface. At 850 ℃, there are a small number of slender needle-like structures on the surface of the film. At 950 ℃, the morphology of the crystal grains transforms into large flaky particles. A sharp uplifted structure appears at the grain boundary. The flaky grain structure is the crystal grains with the C axis perpendicular to the film surface, and the needle-like structure is the random orientation of the C axis in the BaM plane, the sharp warped structure may be due to the miscellaneous phases caused by grain boundary segregation. The needle-like and sharp warped structure will cause the surface roughness of the film to increase. The results of the hysteresis loop test show that the magnetic properties of the thin film annealed at 900 ℃ are the best, with a surface roughness of 2.8 nm, a squareness ratio of 0.84, a saturation magnetization of 247 emu/cm³, and a coercivity of 1 528 Oe.

Multiferroic Enhancement and Bandgap Tuning of Gd³⁺ and Co³⁺ Co-Doped Bismuth Ferrite Thin Films

MA Guobin, YANG Song, XU Lei, GUO Kaixin, WANG Xu

2021, 50(5):  851-857. 

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Multiferroic functional materials are of significant importance in modern daily life and industry. Here we report a multiferroic functional material Bi_0.85Gd_0.15Fe_1-x Co_xO₃(x=0, 0.04, 0.08, 0.12) thin film which was synthesized on Pt/Ti/SiO₂/Si and ITO substrates by sol-gel process, involving ferroic nitrate, bismuth nitrate, gadolinium nitrate, cobalt nitrate as raw materials, ethylene glycol methyl ether as solvent, and citric acid as chelating agent forming precursor solution. A comprehensive investigation of structure, ferroelectric property, magnetic property and optical band gap of Gd³⁺ and Co³⁺co-doping BiFeO₃ was conducted. XRD results reveal that all films showing a rhombohedral structure in the (111) direction, and SEM results exhibit that co-doping could refine the grains. According to the results of ferroelectricity and leakage current test analysis, the maximum residual polarization value reaches 2P_r =15.71 μC/cm² when the Co³⁺ doping amount is 8%, at which amount also achieves the maximum saturation magnetization 37.78 emu/cm³. The leakage current conduction mechanism of all samples is ohmic conduction mechanism. Last but not least, a modulated bandgap effect according to the absorption spectrum and the fitting results of the Tauc formula were observed. In the co-doping film, the optical bandgap gradually decreases with the increase of the doping amount. In particular, when the Co³⁺doping amount is 12%, the optical bandgap decreases to 1.96 eV.

Effects of the Substrate Heating Temperature on Properties of ITO Films

WANG Xinyue, ZHANG Zhaocheng, LI Zhijie, HE Wanting, WEN Jinxiu, LUO Jianyi, TANG Xiufeng, WANG Yi

2021, 50(5):  858-865. 

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Indium tin oxide (ITO) films have been widely used as transparent conductive electrodes for optoelectronic devices. Its light transmittance, electrical conductivity, surface roughness, work functions matching with substrates and carrier transferring performance at the interface all affect the performance of optoelectronic devices. In this paper, ITO films were prepared by RF magnetron sputtering. Influences of substrate heating temperature on properties of ITO films were systematically studied. The Sn doped indium oxide ceramic target was used, the composition molar is m(In₂O₃)∶m(SnO₂)=90∶10. The prepared films were characterized by XRD and SEM, and effects of different substrate temperatures on the crystallization and morphology properties of ITO films were studied respectively. The effects of substrate temperature on the photoelectric properties, carrier concentration, work function and carrier transferring properties of ITO films were studied by UV-Vis spectrophotometer, Hall effect tester, ultraviolet photoelectron spectrometer (UPS) and current-voltage curve, respectively. It is found that the comprehensive properties of the ITO film are the best when the substrate temperature is located at 200 ℃. At this time, the ITO film has good crystallinity, smooth surface, average transmittance over 80% in visible light band, excellent conductivity and current transmission characteristics, and the composition of the film is consistent with that of the target.

Field Emission Characteristics Based on Monomer Graphite Fiber

HUO Haibo, ZHENG Yajuan, MA Huali, DONG Zihua, LI Qianqian, LI Mingyu, DING Pei, ZENG Fanguang

2021, 50(5):  866-870. 

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Field emission cold cathode electron source has a wide range of application prospects in many vacuum electronic devices. Carbon materials suitable for cold cathode materials include carbon nanotubes, carbon microtubes and carbon fibers. Field emission characteristics based on single graphite fiber were studied. Single graphite fiber (MGF) was synthesized by chemical vapor deposition (CVD) in a tubular furnace with methane as carbon source. The DC field emission test was carried out in a vacuum chamber by building a diode structure. A single graphite fiber with a length of 3.426 mm and a spherical radius of 11.26 μm was selected and fixed on the copper plate as the cathode, and a conductive ITO glass was used as the anode. The opening field strength of MGF is confirmed to be 0.477 5 V/μm. Furthermore, the electromagnetic field was analyzed based on the simulation software of ANSYS. The effective emission area of MGF under different voltages was calculated. The results show that when the voltage is 5.36 kV, the maximum emission area of MGF is 796.226 μm² and the average emission current density can reach 46.069 A/cm² in the experimental voltage range. The monomer graphite fiber has good field emission characteristics.

Luminescence Properties and Energy Transfer Mechanism of Pb²⁺ Doped CaMoO₄∶Dy³⁺,Eu³⁺ Phosphors

HU Bin, GUO Liang, YANG Shumin, CAO Liping

2021, 50(5):  871-876. 

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Pb²⁺ doped CaMoO₄∶Dy³⁺,Eu³⁺ phosphors were synthesized by coprecipitation method. The phase composition, luminescence characteristics and energy transfer efficiency between activated ions were characterized and analyzed by X-ray diffractometer and fluorescence spectrophotometer. The results show that the CaMoO₄∶Dy³⁺,Eu³⁺doped with Pb²⁺ phosphor samples have no new diffraction peaks compared with the undoped phosphor samples. The above shows that Pb²⁺ is a good substitute for Ca²⁺ enters into the crystal lattice. The unit cell parameters are a=b=0.548 9 nm, c=1.275 3 nm, Z=2 belongs to the tetragonal crystal system for CaMoO₄∶0.05Dy³⁺,0.15Eu³⁺,0.15Pb²⁺ phosphor. Under the excitation of 391 nm wavelength, it can be seen that 484 nm blue light emission peak attributes to Dy³⁺(⁴F_9/2→⁶H_15/2), 575 nm is the yellow light emission peak produced by Dy³⁺ (⁴F_9/2→⁶H_13/2) transition, 593 nm is the orange light emission peak produced by Eu³⁺ (⁵D₀→⁷F₁) transition, and 619 nm is the red light emission peak produced by Eu³⁺ (⁵D₀→⁷F₂) transition. The critical transfer distance between Dy³⁺ and Eu³⁺ in CaMoO₄∶Dy³⁺,Eu³⁺ phosphors can be obtained by calculation, which is 1.542 6 nm. The energy transfer mechanism is dipole-quadrupole interaction, the energy transfer efficiency is close to 60.31%, and the maximum sample energy transfer efficiency increases to 72.40% for Pb²⁺ doped phosphor. Therefore, it is concluded that doping with Pb²⁺ can greatly increase the energy transfer efficiency between Dy³⁺ and Eu³⁺ and improve the luminous performance of phosphors, so it has important research significance in the field of white LEDs.

Synthesis, Crystal Structure and Properties of Nickel Coordination Polymer with 1,3,5-Tris(Carboxymethoxyl)Benzene

HUANG Qiuping, ZENG Zhenfang, ZHENG Yanfei, LI Lan, HUANG Wei, WEI Youhuan

2021, 50(5):  877-883. 

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A novel metal coordination polymer [Ni(TB)₂(H₂O)₂]_n·2H₂O (H₃TB=1,3,5-tris (carboxymethoxyl)benzene) was constructed under solvothermal conditions, with 1,3,5-tris(carboxymethoxyl)benzene as the directional ligand, reacted with nickel acetate. The structure of polymer was characterized by elemental analysis, IR and X-ray single crystal diffraction. The thermal stability, fluorescence properties and Hirshfeld surface forces were also studied. Single crystal structure analysis show that, the crystal system and space group of the complex is triclinic and $P \overline{1}$. The central ion Ni(Ⅱ) of the complex is six coordinated by with O atoms of carboxylic acid from four different 1,3,5-tris(carboxymethoxyl)benzene ligands, O atoms of two water molecules to give a octahedral geometry NiO₆. A one-dimensional chain configuration with holes is formed by the coordination of oxygen atom with 1,3,5-tris (methoxycarboxyl) benzene. The fluorescence and TG results show that the complex have good fluorescence properties and thermal stability. Hirshfeld surface analysis results reveal that the O…H/H…O interactions is 39.0% contribution to the total Hirshfeld surface of the complex molecules, while H…H and O…O interactions is 25.9% and 13.6%, respectively.

Synthesis, Crystal Structure, and Electrochemical Properties of a Ox-Functionalized Zirconium(Ⅳ) Substituted Tungsten-Oxo Cluster

ZHANG Zhong, YANG Lin, LI Xiaohui, WANG Zilan, WANG Jingyi

2021, 50(5):  884-888. 

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Under hydrothermal conditions,a new Ox-functionalized zirconium(Ⅳ) substituted tungsten-oxo cluster, H₁₂Na₂[Zr₄(μ₃-O)₂(μ₂-OH)₂(Ox)₂(α-SiW₁₀O₃₇)₂]·22H₂O (Ox=oxalic acid) was successfully obtained and characterized by single crystal X-ray diffraction analysis, IR, TG and elemental analysis. The title compound consists of a sandwich-type tungsten-oxo cluster unit built by two divacant {α-SiW₁₀O₃₇} fragments linked through a {Zr₄(μ₃-O)₂(μ₂-OH)₂(Ox)₂} cluster and crystallizes in the monoclinic system, space group P2₁/c with a=2.132 2 (6) nm, b=1.271 6 (4) nm, c=2.223 1(7) nm, β=110.933(4)°, V=5.629 9(3) nm³, Z=2, R₁=0.061 5, wR₂=0.164 4. The electrochemistry and electrocatalytic properties of the title compound were studied, and it exhibits excellent catalytic activities for NO^-₂ reduction.

Synthesis, Crystal Structure and Fluorescent Properties of Ni(Ⅱ) Complex with Benzo[d]Imidazole Ligand

ZHAO Mingxia, XIONG Liqin, CHANG Jin, ZHAO Zhiju, QI Chuanmin

2021, 50(5):  889-893. 

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A nickel complex with a three-dimensional supramolecular structure was synthesized through mixed solvent refluxing method using 3-(4-carboxyphenyl)-7-methyl-2-propyl-3H-benzo[d]imidazole-5-carboxylic acid and NiCl₂·6H₂O as raw material. Its structure and property were characterized by X-ray single crystal diffraction, elemental analysis, IR, UV-Vis and fluorescence spectra. Single crystal X-ray diffraction studies reveal that the complex is in the triclinic system, space group of P1 with a=0.778 5(16) nm, b=1.126 6(2) nm, c=1.175 6(2) nm, α=113.63(3)°, β=93.24(3)°, γ=101.00(3)°, V=0.917 1(3) nm³. The title complex is a mononuclear complex which consists of four ligand anions that connect the center Ni(II) cation to form a one-dimensional ring chain, and further forms a three-dimensional supramolecular structure through hydrogen bonding and π-π stacking. Fluorescence spectrum analysis shows that both the ligand and the title complex have good fluorescence properties, and the fluorescence properties of the title complex are better than that of the ligand.

Synthesis, Crystal Structure and Magnetic Properties of 1D Cobalt Naphthalene Phosphonate Carboxylate Complex

XU Yan, CUI Lei, BU Kang

2021, 50(5):  894-899. 

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Self-assembly of naphthalene phosphonate carboxylate ligand and cobalt(Ⅱ) chloride hexahydrate, 1D coordination polymer, namely [Co(5-pncee)(4,4′-bpy)(H₂O)₃(5-pnceeH₂)]·2H₂O(1) (5-pnceeH₂=5-phosphono -naphthalene-1-carboxylic acid ethyl ester, 4,4′-bpy=4,4′-bipyridinyl) was hydrothermally synthesized and 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 triclinic system, space group of P1, a=0.824 06(6) nm,b=1.014 48(9) nm, c=1.151 44(8) nm. It shows a linear chain structure. The neighboring chains are connected by moderately strong hydrogen bonds forming a supramolecular layer. The interlayer spaces are filled with the organic groups of the phosphonate ligands. Magnetic properties were investigated for compound 1, it is found that there is spin orbit coupling and/or antiferromagnetic interaction between Co(II) ions.

Orthogonal Experimental Study on Circular Arc Machining of Hard and Brittle Materials with Diamond Wire Saw

WANG Yashuai, WANG Yanqing, YANG Shengqiang

2021, 50(5):  900-907. 

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In order to solve the problem of shape cutting hard brittle material disc parts, a shape cutting method based on electroplated diamond wire saw was proposed and the cutting experiment was carried out. The effects of cutting speed V(A), rotating speed n(B) of rotary table W axis and tension force F(C) of diamond wire saw on radial runout, wire bow angle, cutting efficiency and surface roughness of circular arc surface were studied systematically by using three factor and four level orthogonal test. The results show that the influence of W-axis speed on the radial runout (roundness), cutting efficiency and surface roughness of arc is the largest, followed by the tension force and the linear velocity. The influence of tension force on the wire bow angle is the largest, followed by the linear velocity and the W-axis speed is the smallest. In the range of the test conditions, the optimal combination of process parameters are A3B1C1, that is, the linear speed of diamond wire saw is 8.96 m/s, the rotating speed of rotary table is 0.25 r/h, and the tension force is 12 N. The range analysis results of radial runout, wire bow angle, cutting efficiency and surface roughness are consistent with their variance results.

Effects of Different Ions in Dolomite Refining Solution on Calcium Carbonate Whiskers

WANG Dongyi, ZHENG Qiang, YU Yajie, XU Shaowei, WANG Yubo, DENG Xiaoyang, CAO Xiaoning, YUE Yan, LI Xue, LIU Yunyi

2021, 50(5):  908-914. 

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Dolomite mineral deposits are abundant and widely distributed in our country.Calcium carbonate whiskers were prepared by gas-liquid contact method using dolomite refining solution and carbon dioxide as experimental raw materials. The effects of impurity ions Mg²⁺, NH⁺₄ and NO^-₃ on the aspect ratio and morphology of calcium carbonate whiskers were studied. Morphology and phase structure of the products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the morphology and aspect ratio of calcium carbonate whiskers are the best when the concentration of NH⁺₄ is 0.3 mol/L, the concentration of Mg²⁺ is 0.05 mol/L, and the concentration of NO^-₃is 0.2 mol/L, the aspect ratio reaches above 25 at the highest. Finally, the crystallization process and growth mechanism of calcium carbonate whiskers are explained by combining with crystal growth theory.

Preparation and Electrochemical Properties of Nickel Hydroxide/Reduced Graphene Oxide Composites

ZHANG Jie

2021, 50(5):  915-919. 

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Ni(OH)₂/RGO composite electrode materials were prepared from nickel nitrate and graphene oxide by one-step hydrothermal reduction using porous nickel foam as substrate, urea as precipitant and hexadecyl trimethyl ammonium bromide (CTAB) as dispersant. The morphology and structure of Ni(OH)₂/RGO electrode materials were characterized, and the electrochemical properties of the materials were investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests. The crystal forms of Ni(OH)₂ and Ni(OH)₂/RGO were determined by X-ray diffraction (XRD) analysis. SEM images show that the silky RGO sheets are effectively and uniformly distributed on the surface of Ni(OH)₂ layer. During the hydrothermal process, Ni(OH)₂ sheets grow in situ on the nickel foam, forming a three-dimensional porous multi-layer diversified structure. Compared with pure Ni(OH)₂, the specific capacitance of pure Ni(OH)₂ at 1 A/g is 1 930 F/g and the specific capacitance of Ni(OH)₂/RGO is 2 508 F/g. These results indicate that Ni(OH)₂/RGO is a promising electrode candidate material for supercapacitor.

Preparation of La₂O₃ Slag Glass-Ceramics by Microwave Heating

ZHAO Guangkai, XU Wence, LIU Saiyu, ZHANG Yuxuan, WU Nannan, LIU Fang, OUYANG Shunli

2021, 50(5):  920-926. 

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Using slag to prepare slag glass-ceramics is one of the main ways to improve the utilization rate of mineral resources. CaO-MgO-Al₂O₃-SiO₂(CMAS) series pyroxene phase slag glass-ceramics were prepared using Bayan Obo tailings as raw materials by microwave one-step method. 835 ℃ was choosed as the crystallization temperature and the influence of microwave heating on the crystallization behavior and microstructure of glass-ceramics were studied. Effect of La₂O₃ addition on the crystallization behavior of slag glass-ceramics were discussed using La₂O₃ as the research variable. Compared with traditional heat treatment system, the microwave heating achieves higher crystallization effect in a shorter time. Here, the addition of La₂O₃ promotes grain refinement. According to the analysis of Raman spectroscopy, the addition of La ion will cause the increase of bridging oxygen in the glass network and increase the tightness and integrity of the crystal. The hardness is the highest when the addition of La is 4% (mass fraction), and the Vickers hardness reaches 829.22 MPa.

Effect of Nano-SnO₂ or Nano-Yb₂O₃ on Crystallization Property of Fused Quartz Ceramics

GU Yinglei, LI Yong, BU Jinglong, MA Chao, WANG Zhifa

2021, 50(5):  927-932. 

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Effects of nano-SnO₂ or nano-Yb₂O₃ on crystallization property of fused quartz ceramics were studied by XRD and measurement of thermal expansion rate from the perspective of crystallization. The results indicate that cristobalite as the main crystal phase would crystallized in the fused quartz glass at high temperature, and the amount of cristobalite increases with increasing of sintering temperature; the addition of nano-SnO₂ or nano-Yb₂O₃ effectively decreases the expansion ratio of the fused quartz ceramic materials during temperature elevating process by inhibiting crystallization of cristobalite, and with increase of sintering temperature, the dosage of additive necessary to keep the fused quartz ceramic materials with a low expansion ratio was adjusted, the optimum dosage (mass fraction) of nano-SnO₂ or nano-Yb₂O₃ as crystallization inhibitors is 1% and 2%, respectively.

Thermophysical Performances of (Sm_0.5Gd_0.2Nd_0.3)₂(Hf_0.3Ce_0.7)₂O₇ Composite Oxides

RAN Shuming, GUO Yi

2021, 50(5):  933-937. 

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In order to develop novel ceramic material for thermal barrier coatings, the (Sm_0.5Gd_0.2 Nd_0.3)₂(Hf_0.3Ce_0.7)₂O₇ composite oxides were synthesized by high temperature sintering method in this paper. Its lattice-type was analyzed by XRD, the microstructure was analyzed by SEM, thermal expansion property was tested by thermal expansion instrument, and thermal diffusivity was measured by laser thermal laser conductor-meter. Results show that the pure (Sm_0.5Gd_0.2Nd_0.3)₂(Hf_0.3Ce_0.7)₂O₇ with single fluorite lattice was synthesized. The microstructure is very dense, and interfaces between boundaries are very clean, no other phases can be found. Owing to the complex element constituent and high atomic weight, its thermal conductivity is lower than those of 7YSZ and Sm₂Ce₂O₇. The relative low thermal expansion coefficient of (Sm_0.5Gd_0.2Nd_0.3)₂(Hf_0.3Ce_0.7)₂O₇ can be contributed to the lower ionic radius of cations at B sites, while the thermal expansion coefficient meets to the requirement for thermal barrier coatings.

Optimization of Boundary Damage Length in Ultrasonic Vibration Assisted Electrolytic in-Process Dressing Internal Grinding of ZTA Ceramics by Response Surface Methodology

JIA Xiaofeng, LIU Yuhui

2021, 50(5):  938-946. 

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Experiment of ultrasonic vibration assisted electrolytic in-process dressing internal (UAEI) grinding for zirconia toughened alumina (ZTA) ceramics was carried out based on Box-Behnken design method of response surface methodology, and response surface model was established. The influence law of four process parameters of electrolytic in-process dressing (ELID) power supply voltage, grinding depth, axial feed and wheel speed and their interaction on the boundary damage length was studied through significance test, response surface plot and contour map obtained from experiments. The influence intensity of significant factors on response value was obtained by analyzing the response surface plot and contour map obtained from response surface model, and the cause of the interaction influence on response value was also analyzed. The influence intensity of significant factors on response value in descending order are grinding depth, ELID power supply voltage, axial feed and wheel speed. The influence intensity of interaction of factors combination on the response value in descending order are interaction between grinding depth and grinding wheel speed, interaction between axial feed and grinding wheel speed, interaction between ELID power supply voltage and grinding depth, interaction between grinding depth and axial feed. Taking the minimum boundary damage length as the optimization objective, the optimal combination of parameters of UAEI grinding for ZTA ceramics are as follows: ELID power supply voltage is 86.39 V, grinding depth is 1.55 μm, axial feed is 81.24 mm/min, wheel speed is 2 741.41 r/min, and the theoretical prediction value of optimal boundary damage length is 6.537 μm. The relative error is within a reasonable range by experimental verification. The response surface model has a higher precision and provides some reference for reasonable selection of process parameters of UAEI grinding.

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Research Progress on Transition Metal Ions Doped Ⅱ-Ⅵ Group Mid-Infrared Laser Ceramics

LUO Yongzhi, YU Shengquan, YIN Ming, KANG Bin

2021, 50(5):  947-958. 

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The mid-infrared laser at 2~5 μm is widely used in civil and military fields. It is one of the main ways to generate mid-infrared lasers by direct-pumping the laser gain medium. Because of the unique spectral properties, ZnS or ZnSe doped by the divalent transition metal ions of Cr²⁺ or Fe²⁺ (TM²⁺∶Ⅱ-Ⅵ) is one of the most promising mid-infrared laser gain materials. In this paper, the preparation of TM²⁺∶Ⅱ-Ⅵ materials are firstly summarized, and then the research progress on TM²⁺∶Ⅱ-Ⅵ laser ceramics is emphatically introduced. At last, the further research in raw materials and sintering is discussed. This paper could promote the development of TM²⁺∶Ⅱ-Ⅵ laser ceramics as well as the high performance mid-infrared lasers.

Current Status of Electron Transport Layer in Perovskite Solar Cells

XING Shulin, HE Yunfei, HE Jizhuang, LI Jiahua, FU Chunlin

2021, 50(5):  959-966. 

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The highest photoelectric conversion efficiency of organic-inorganic hybrid perovskite solar cells (referred to as perovskite solar cells) has reached 25.5%, and it is one of the most promising solar cells to replace silicon-based solar cells and achieve a wide range of applications. As the basic component of the perovskite solar cell, the electron transport layer plays a vital role in the performance of the cell. This article briefly describes the effects of type(organic polymer materials and metal oxides such as TiO₂, ZnO and SnO₂) of electron transport layers in perovskite solar cells, size (the length and diameter of the nanowires, the thickness of the thin films) and interface modification on the performance of the devices.This can provide a reference for the works of continuing to improve the performance of perovskite solar cells.

Research Progress on Low Crack Damage Slicing Technology for Single Crystal Silicon

GE Mengran, BI Wenbo

2021, 50(5):  967-973. 

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The developing trend in the IC manufacturing field is to increase the wafer diameter, decrease the wafer substrate thickness and decrease the semiconductor manufacturing process technology. As the semiconductor manufacturing process technology decrease to 5 nm, the requirement of wafer substrate quality of single crystal silicon is higher and higher. Slicing is the first machining process in chip substrate wafer manufacturing, and the diamond wire saw slicing is the main technology for the large size single crystal silicon slicing. In this paper, the development prospects and challenges of diamond wire saw slicing technology are introduced. The material removal mechanism of diamond wire saw slicing based on the single crystal silicon scratching and the 3D morphology modeling technology of electroplated diamond wire saw are presented. The mechanism of sliced wafer surface generation and crack damage are summarized. The technological measures of low crack damage slicing of single crystal silicon are prospected. The development trend of single crystal silicon slicing technology is pointed out. It is of great significance to the development of IC manufacturing technology.