Table of Content

15 August 2023, Volume 52 Issue 8

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Research Articles

Optical and Electrical Properties of Ni-Doped β-Ga₂O₃ Single Crystal

CHEN Shaohua, MU Wenxiang, ZHANG Jin, DONG Xuyang, LI Yang, JIA Zhitai, TAO Xutang

2023, 52(8):  1373-1377. 

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Ni-doped β-Ga₂O₃ single crystals were grown by edge-defined film-fed growth (EFG) method, and the crystal structure and quality were verified by powder X-ray diffraction (PXRD) and Laue diffraction. The effect of Ni²⁺ doping on optical properties of β-Ga₂O₃ was investigated by UV-Vis-NIR transmission spectra and infrared transmission spectra. It is found that the ultraviolet cut-off edge of (100) plane is 252.9 nm and corresponding optical bandgap is 4.74 eV. Furthermore, the broadband near-infrared luminescent property of Ni-doped β-Ga₂O₃ was discovered by cathodoluminescence (CL) spectroscopy in the range from 600 nm to 800 nm, which is expected to broaden the application of β-Ga₂O₃ crystal in broadband near-infrared.

Stress Field Analysis of Diamond Wire Sawing β-Ga₂O₃ Crystal

LI Zongping, CHENG Dameng

2023, 52(8):  1378-1385. 

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As a typical hard and brittle material, gallium oxide crystal (β-Ga₂O₃) is easy to crack during processing. Diamond wire saw is the main way to produce β-Ga₂O₃ wafers. During the slicing process, a microcrack damage layer will be generated on the surface of the wafer. Under the stress, the microcracks will expand, leading to material breakage and fracture. In this paper, a finite element model of diamond wire sawing of β-Ga₂O₃ (010) crystal surface was established. The distribution of mechanical stress, thermal stress, and thermal-mechanical coupling stress during the sawing process were studied. The effects of sawing wire speed, feed speed and different parameter combinations under constant speed ratio on the thermal-mechanical coupling stress were analyzed. The research results show that: the thermal stress generated by sawing heat dominates the thermal-mechanical coupling stress during the sawing process; the mechanical stress caused by sawing force has a small numerical value and proportion, but it affects the distribution of thermal-mechanical coupling stress; increasing sawing wire speed and feed speed will increase the thermal-mechanical coupling stress.

Effect of Composition Step-Graded InGaN Barriers on Photoelectric Performance of Green Laser Diode

HOU Yanyu, DONG Hailiang, JIA Zhigang, JIA Wei, LIANG Jian, XU Bingshe

2023, 52(8):  1386-1393. 

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In order to investigate the influence of In_xGa_1-xN barrier with different indium (In) composition on photoelectric performance of green laser diode, a series of green laser diode with In_xGa_1-xN barrier of different In composition were simulated by SiLENSe (simulator of light emitters based on nitride semiconductors) software. The results show that the In_xGa_1-xN barrier structure with 3% In composition has the highest slope efficiency and the lowest internal optical loss, and also show the largest optical confinement factor and the optimum performance. Based on the multiple quantum well structure with In_0.03Ga_0.97N barrier, the composition step-graded (CSG) InGaN barrier model structure was designed, which effectively improves the slope efficiency and electro-optical conversion efficiency. Moreover, the optical field confinement increase. The simulation results show that at the injection current of 120 mA, the efficiency of electro-optical conversion increases from 17.7% to 19.9% for the multiple quantum well structure with CSG InGaN barrier, the slope efficiency increases from 1.09 mW/mA to 1.14 mW/mA, and the optical confinement factor increases from 1.58% to 1.62%. The study provides theoretical guidance and data support for the preparation of high-power GaN-based green laser diode.

Effect of Biaxial Strain on Electronic and Optical Properties of Single-Layer CdZnTe

NIE Fan, HAN Shuo, ZENG Dongmei

2023, 52(8):  1394-1399. 

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Studying the effect of biaxial strain on the electronic and optical properties of single-layer CdZnTe semiconductor materials provide theoretical support for the preparation of CdZnTe devices with excellent optical properties. In this paper, a single-layer CdZnTe model was built with the Material Studio software, and strain is applied to the model in the (100) and (010) directions. Based on the first-principle of density functional theory, the effects of biaxial strain on the band gap, effective mass of carrier, mobility and dielectric constant of single-layer CdZnTe were simulated and calculated. The results show that both tensile and compressive strains reduce the band gap of the single-layer CdZnTe, and biaxial strain effectively control the effective mass, mobility and dielectric constant of carriers. Compared with the tensile strain, compression strain of the same size has more obvious effect on the properties of the single-layer CdZnTe. With the increase of applied biaxial compression strain, the band gap of the single-layer CdZnTe gradually decreases, which leds to the increase of wavelength range of absorption light of the CdZnTe semiconductor, and the carrier effective mass and mobility of single-layer CdZnTe show an overall downward trend. Also, the increase of applied biaxial compression strain makes the real part of the dielectric constant gradually decrease and the imaginary part of the dielectric constant gradually increase, which enhances the metallicity of the single layer CdZnTe and improves its optical performance.

Structural Simulation and Optical Property Prediction of Au, Cu, and Sb Doped CdTe Based on First-Principles

ZHANG Pingwei, LIN Long, ZHANG Zhanying

2023, 52(8):  1400-1406. 

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The electronic and optical properties of Au, Cu, Sb doped CdTe systems were studied based on density functional theory. Au, Cu and Sb doped CdTe systems all exist stably. The hybridization of transition metal atoms with Cd atomic orbitals reduces the band gap of CdTe and improves the utilization of visible light by CdTe. The lower energy required to jump from the valence band to the conduction band promotes the migration of more photogenerated electrons, which greatly improves the optical properties of doped CdTe. Among the three systems, Sb/CdTe system shows the most significant increase of absorption coefficient in the visible light range, with photogenerated electron and hole mobilities increasing by a factor of 5.97 times and 15.54 times compared with CdTe system, respectively. The mechanism of the enhancement of the optical properties of Au, Cu, and Sb doped CdTe is theoretically revealed by calculating the band, density of states, electron population, optical absorption function, and carrier mobility.

Effect of Dy and Lu Doping on Magneto-Optical Properties of TSAG Crystal

ZHANG Ronggui, CHEN Tengbo, LI Laichao, LI Yuhu, MA Yanli

2023, 52(8):  1407-1412. 

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Tb₃Sc_xAl_5-xO₁₂(TSAG) crystal is a magneto optical crystal material with excellent performance. Solving the cracking problem during the growth of large-sized TSAG crystal is of great significance for its application in high-power magneto-optical isolators. The segregation law of Dy and Lu during the crystal growth process with Czochralski method was investigated, and the effect of Dy and Lu doping on the crystal properties TSAG were also clarified. The results indicate that Dy and Lu doping are helpful to solve the cracking problem of large-sized TSAG crystal. The obtained TSAG crystals have good internal quality, and the resulting extinction ratios are all greater than 33 dB. Lu doping improves the Verde constant of TSAG crystals, while Dy doping has no significant effect on the Verde constant of TSAG crystals. The magneto-optical properties of Dy and Lu co-doped TSAG crystals are basically similar to those of TSAG, and the prepared crystals meet the requirements for high-power laser isolators.

Two-Dimensional Kagome Magnetic Material Fe₃As with Large Magnetic Anisotropy and High Curie Temperature

HUANG Tian, MA Sai, LIU Xiaoyu, LI Ying, WU Hong, XU Yongbing, WEI Lujun, LI Feng, PU Yong

2023, 52(8):  1413-1421. 

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Recently, the exploration of two-dimensional (2D) ferromagnetic materials has become a hot topic in the field of spintronic devices. In this work, Fe₃As, a new two-dimensional material, with Curie temperature (T_c) of 300 K (reach room temperature), was designed by means of spin-polarized density generalization theory calculations. The predicted 2D Fe₃As has strong in-plane Fe—Fe coupling with large magnetic anisotropy energy (MAE) of approximately 366.7 μeV, which contributes to maintain a long-range ferromagnetic order. The energy band of Fe₃As has both flat band and Dirac point features. The position of the flat band is positively related to the strength of the magnetic coupling. Furthermore, T_c increases progressively as the distance between the flat band and the Fermi surface continues to decrease under the effect of the biaxial strain. Therefore, Fe₃As monolayer is considered to be a promising candidate for 2D room-temperature spintronics devices.

Thermoelectric Properties of the Novel Thermoelectric Material Y₂Te₃ Through Strain Modulation

XIA Yuhong, YANG Zhenqing, ZHOU Lulu, SHAO Changjin

2023, 52(8):  1422-1431. 

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The rare-earth chalcogenides Y₂Te₃ with low lattice thermal conductivity is a very promising novel thermoelectric material. Applying strain is an effective way to modulate the thermoelectric properties of thermoelectric materials. In this paper, first-principles approach combined with the semiclassical Boltzmann transport theory were used to study the strain modulation of the thermoelectric properties of Y₂Te₃ materials, for which -4% to 4% strain was applied to the Y₂Te₃ materials. The results show that applying compressive strain may modulate thermoelectric properties more effectively than tensile strain. The maximum power factor of p-type Y₂Te₃ increases from 0.4 mW·m^-1·K^-2 to 1.6 mW·m^-1·K^-2 at 300 K, and the maximum power factor of n-type Y₂Te₃ increases from 8 mW·m^-1·K^-2 to 11 mW·m^-1·K^-2 under compressive strain. The maximum thermoelectric figure of merit (ZT) of p-type Y₂Te₃ increases from 0.07 to 0.15 under strain modulation at 300 K, and the maximum ZT of n-type Y₂Te₃ increases from 0.7 to 0.9 under compressive strain. Therefore, n-type Y₂Te₃ has very excellent thermoelectric properties, and the thermoelectric properties of Y₂Te₃ materials can be effectively regulated by applying strain. n-type Y₂Te₃ has great potential as a thermoelectric material.

Low-Frequency Band Gap of Novel Two-Dimensional Phonon Crystal and Its Formation Mechanism

HU Peizhou, ZHAO Jingbo, LIU Hong, ZHANG Xiaosheng, HAN Donghai, YAO Hong, ZHANG Guangjun

2023, 52(8):  1432-1440. 

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A new two-dimensional phonon crystal structure was designed and studied deeply by finite element method and equivalent model method. It is found that the structure has good low-frequency sound absorption performance. Through theoretical derivation and simulation calculation, it is found that the structure has a complete four band gap within 0~800 Hz under the condition of lattice constant of 21 mm. The lower limit of the first band gap is as low as 40.28 Hz, and the bandwidth is approximately 93 Hz. Sound transmission loss calculation shows that the structure has a good acoustic insulation effect in the low frequency domain, and the maximum sound insulation amount can reach 87.31 dB. After analyzing the multiple vibration modes of the structure, the corresponding equivalent model is established, and the influence of different factors on the band gap is explored based on the equivalent model. The general regularities of the new two-dimensional phonon crystal are summarized. The results show that increasing the scatterer density and reducing the matrix density can increase the bandwidth, and increasing the filling rate and properly opening the scatterer can improve the band gap characteristics. The research may provide some ideas for solving low-frequency noise control problems in engineering application.

Low-Frequency Sound Insulation Characteristics of Large-Size Asymmetric Membrane-Type Acoustic Metamaterials

YAN Wenhui, LIU Xixuan, FANG Tianyin, SUN Xiaowei, WEN Xiaodong, OUYANG Yuhua

2023, 52(8):  1441-1450. 

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Aiming at the insulation of low-frequency acoustic sound, a 100 mm crescent disc asymmetric membrane-type acoustic metamaterial structure was designed in this paper, which was composed of aluminum material as the frame and iron material as the mass attached to the surface of flexible ethylene-vinyl acetate copolymer film. The finite element method was adopted to calculate its transmission loss and displacement field. The asymmetric structure, the structure parameters and the mass block′s eccentricity together with the vibrational modes analysis were investigated in this study for a better sound insulation performance. The results show that, compared with the symmetric membrane-type acoustic metamaterials, the design of the asymmetry in a single cell makes the low-frequency sound insulation band widened by 23 Hz. Meanwhile, more vibrational modes are generated which illustrates that the coexistence of Lorentz resonance and Fano resonance promotes a better sound insulation performance of the crescent disc asymmetric structure. The large-size asymmetric membrane-type acoustic metamaterial structure designed in this paper can reduce the sound insulation frequency to 10 Hz with a wide low-frequency sound insulation performance within 10~500 Hz. It provides a new method for improving the low-frequency sound insulation effect of sound barriers in terms of structural optimization design.

First-Principles Study on Nb₂N as Anode Material for Magnesium and Aluminum Ion Batteries

ZHANG Wanhe, HU Jianying, ZHOU Tao, LYU Yiting, WANG Keliang

2023, 52(8):  1451-1457. 

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The development of high-performance two-dimensional anode materials is the key to the application of rechargeable ion batteries. Based on first-principles calculations, the interaction of Mg and Al ions with two-dimensional Nb₂N was systematically studied in this work, including its geometric configuration, electronic structure, ion diffusion characteristics, open-circuit voltage, and theoretical capacity. Both Mg and Al ions can be adsorbed on two-dimensional Nb₂N, and the adsorption energy is negative, indicating that metal ions have strong binding effect with two-dimensional Nb₂N, which is conducive to the application in rechargeable ion batteries. The metallic properties of two-dimensional Nb₂N ensure that the ion batteries maintain good conductivity. The diffusion barrier of the two ions is less than 0.2 eV, indicating that they have good charge and discharge rates. In addition, both magnesium ion and aluminum ion batteries have relatively low open-circuit voltage and high theoretical capacity. These results show that two-dimensional Nb₂N is suitable for the use of magnesium ion and aluminum ion batteries as high-performance anode materials.

Effect of Sputtered NiO_x Modified by Self-Assembled Layer on Performance of Blade-Coated Wide-Bandgap Perovskite Solar Cells

LI Jianing, GE Xin, HUANG Zixuan, LIU Zhen, WANG Pengyang, SHI Biao, ZHAO Ying, ZHANG Xiaodan

2023, 52(8):  1458-1466. 

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As a common inorganic hole transport layer material in high efficiency perovskite solar cells, nickel oxide (NiO_x) has good optical transmission and chemical stability, and can also be prepared by magnetron sputtering and other scalable manufacturing methods at low cost. However, compared to organic hole transport materials, the energy level mismatch, defects, and adverse chemical reactions at the NiO_x/perovskite interface deteriorate the performance of NiO_x-based wide-bandgap perovskite solar cells (PSCs). To address these issues simultaneously, a self-assembled layer of (2-(9H-carbazol-9-yl) ethylphosphonic acid (2PACz) was proposed as NiO_x/wide-bandgap perovskite interface modification material. This molecule can passivate NiO_x surface traps, optimize the film formation of the upper perovskite layer and facilitate charge transport. Consequently, the power conversion efficiency (PCE) of wide-bandgap PSCs increase from 16.18% to 18.42%. This work provides a reference strategy for the application of NiO_x hole transport layer in wide-bandgap PSCs.

Preparation and Photocatalytic Properties of K₃ScF₆∶Tm³⁺, Yb³⁺/CdS Photocatalytic Composites

SHUAI Pengfei, HUANG Feifei, GUO Qingfeng, LIAO Libing, MEI Lefu

2023, 52(8):  1467-1476. 

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The combination of up-conversion materials and photocatalysts can produce the effect of “redshifting” of absorption spectrum, which is of great significance for improving the degradation efficiency of photocatalysts. To improve the utilization of CdS in near-infrared light, the up-conversion luminescent material K₃ScF₆∶Tm³⁺,Yb³⁺ with cryolite structure was synthesized by high-temperature solid-phase reaction method, and a new photocatalytic composite material K₃ScF₆∶Tm³⁺,Yb³⁺/CdS was prepared by combining it with CdS by high-energy ball milling method. The composition, structure and properties were systematically characterized by X-ray powder diffractometer (XRD), field emission scanning electron microscopy (SEM), fluorescence spectroscopy (PL) and UV-Vis diffuse reflection absorption spectroscopy. Simultaneously, the photodegradation efficiency and mechanism of K₃ScF₆∶Tm³⁺, Yb³⁺/CdS to rhodamine B(RhB) were studied. The results show that the optimal mass composition ratio of K₃ScF₆∶Tm³⁺,Yb³⁺ and CdS is 3.6∶1, and the introduction of up-conversion luminescent materials K₃ScF₆∶Tm³⁺,Yb³⁺ synergistically promots the photocatalytic efficiency of CdS. The ·OH and ·O^2- participated in the degradation of RhB, and ·OH plays a major role. In addition, under the optimal recombination ratio, the degradation rate of K₃ScF₆∶Tm³⁺, Yb³⁺/CdS samples reaches 99.9%, which is nearly 50 times higher than that of uncompounded CdS after 80 min. All results show that K₃ScF₆∶Tm³⁺,Yb³⁺/CdS photocatalytic composites has potential application value in the field of photocatalysis.

Citric Acid-Assisted Solvothermal Synthesis of Bi₂MoO₆ and Its Photocatalytic Performance

MA Zhanqiang, WANG Nan, GUO Wei, ZHANG Kaiyue, LI Juan

2023, 52(8):  1477-1484. 

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The development of efficient visible light-responsive photocatalysts is of great importance to the advancement of photocatalytic technology. Bi₂MoO₆ was prepared via the citric acid (CA)-assisted solvothermal method and characterized by XRD, SEM, UV-Vis DRS, BET, and PL. The photocatalytic performance of the synthesized material was evaluated by ciprofloxacin (CIP) degradation, Escherichia coli (E. coli) and Staphylococcus aureus (S. aures) inactivation under visible light. Bi₂MoO₆ prepared with 3 mmol amount of CA, namely BM-3, exhibits the optimal photocatalytic activity. The CIP degradation efficiency of BM-3 reaches 89.5% within 100 min, which is 2.45 times higher than that of BM-0 prepared without CA. In addition, BM-3 could completely inactivate E. coli within 150 min or S. aures within 200 min, causing concave surfaces and cell aggregation due to the leakage of cellular contents. Multiple cycles of experimentation were conducted to validate the stability of BM-3. The wide visible light absorption range, large specific surface area, and efficient photogenerated carrier separation efficiency were key factors contributing to the superior photocatalytic performance of Bi₂MoO₆ synthesized by the CA-assisted solvothermal method.

Synthesis, Structure and Photocatalytic Properties of a Keggin-Type Polyoxometalate-Based Supramolecular Complex Hybridized by 3-Pyridineacrylic Acid Ligand

SUN Jiaxin, LI Shuang, LI Xiaohui, SHI Siliu, LIU Baohui, QI Jiahui, LI Jiaqi, ZHANG Zhong

2023, 52(8):  1485-1490. 

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A new Keggin-type polyoxometalate-based supramolecular complex 1, namely H₃[(3-PA)₄(PW₁₂O₄₀)] (3-PA=3-Pyridineacrylic acid), was successfully synthesized under hydrothermal conditions and structurally characterized by single crystal X-ray diffraction, elemental analysis (EA), IR spectra, PXRD, TG and UV-Vis diffuse-reflectance. Complex 1 crystallizes in the triclinic system, P-1 space group with a=1.200 33(3) nm, b=1.216 42(3) nm, c=1.424 66(4) nm, α=75.030(1)°, β=73.452(1)°, γ=69.372(1)°, V=1.837 00(8) nm³, Z=1, M_r=3 476.78, F(000)=1 538, μ=18.815 mm^-1, D_c=3.143 mg·m^-3, S=1.062, R₁=0.046 2, wR₂=0.138 7. The structural unit of complex 1 consists of a [PW₁₂O₄₀]^3- ployanion and four 3-PA ligands. In addition, [PW₁₂O₄₀]^3- polyanion and 3-PA ligands are linked by H-bonds to form 2-D supramolecular layer. When using as photocatalyst, complex 1 displayed excellent photocatalytic activity towards the reduction of Cr(Ⅵ) with good structural stability and recyclability.

Effect of High-Valence State W Doping on the Catalytic Activity of NiFe Phosphides for Overall Water Splitting

ZHANG Yiqing, LIANG Junhui, FAN Haoyang, CHEN Da, CHEN Huayu, HUANG Yuexiang, YAO Xin, QIN Laishun

2023, 52(8):  1491-1499. 

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In recent years, the development of photovoltaic assisted electrocatalytic (PV-EC) water splitting has emerged as a critical issue in achieving carbon neutrality through green hydrogen evolution. However, traditional electrocatalysts do not meet the high solar-to-hydrogen (STH) conversion efficiency requirements for PV-EC systems. Therefore, it is crucial to obtain electrocatalysts with low cost and reaction overpotential. In this work, transition metal W with high valence states was employed to dope NiFe phosphide, and NiFeW ternary phosphides were prepared by a simple one-step electrodeposition method. The results indicate that NiFeW phosphide has excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities. Furthermore, when used as a bifunctional electrocatalyst, NiFeW phosphide shows a 51 mV reduction in overpotential at a current density of 10 mA/cm² compared to NiFe phosphide sample. Finally, NiFeW phosphide and a-Si∶H/a-SiGe∶H/a-SiGe∶H solar cell are employed as bifunctional electrocatalyst and driving source, respectively. The PV-EC devices achieve above 7% theoretical STH efficiency, which is significant for practical applications of solar to hydrogen devices.

Preparation of Pt/Cu Alloy Catalyst and Its Hydrogen Evolution Performance in Electrolytic Water

LI Yan, YANG Zhenfeng, FAN Yueyao, ZHANG Xiaoting

2023, 52(8):  1500-1508. 

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In the face of the fossil energy crisis, hydrogen energy has attracted widespread attention because of its cleanness and efficiency. Therefore, hydrogen production by water electrolysis has become a new research upsurge. This research mainly focused on the synthesis, characterization and application of Pt/Cu alloy catalyst. Pt/Cu alloy was synthesized by solvothermal method. The composition, structure and morphology of Pt/Cu alloy were characterized by XRD, SEM, TEM, EDS, XPS, etc, to explore the relationship between its structure and performance. The catalytic performance of Pt/Cu alloy under different electrolyte were tested by electrochemical test system. In 0.5 mol/L H₂SO₄, the initial overpotential of Pt/Cu alloy is 20.3 mV (at 10 mA·cm^-2) and the Tafel is 37.56 mV·dec^-1. At the same time, the initial overpotential and Tafel of Pt/Cu alloy are 35.0 mV (at 10 mA·cm^-2) and 52.12 mV·dec^-1respectively in 1 mol/L phosphate buffered saline (PBS). In addition, the initial overpotential and the Tafel of Pt/Cu alloy are 25.3 mV (at 10 mA·cm^-2) and 36.82 mV·dec^-1respectively in 1 mol/L KOH. It can be found that Pt/Cu alloy exhibits better catalytic performance in acidic electrolyte. Moreover, further experiments show that the Pt/Cu alloy catalyst has high electrocatalytic activity surface area (30.83 cm²) and good cycle stability in acidic electrolyte.

Preparation and Photoluminescence Properties of Sm³⁺-Doped 0.96Na_0.5Bi_0.5TiO₃-0.04CaTiO₃ Ceramics

MA Chunlin, WANG Ziheng, FAN Yuxiang, HU Ying, HU Yazhou

2023, 52(8):  1509-1515. 

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A series of Sm³⁺-doped 0.96Na_0.5Bi_0.5TiO₃-0.04CaTiO₃ (NBT-0.04CT∶xSm³⁺, 0.002≤x≤0.020) lead-free piezoelectric ceramics were prepared by a conventional solid-state reaction method. The phase structures of the samples were characterized by X-ray diffractometry, and all the samples show a single perovskite structure. The photoluminescence properties of the samples were measured by fluorescence spectrophotometer, and the samples show the strongest excitation peak at 479 nm, which matches well with the blue LED chip used in the white LED synthesis. The dominant emission peak is located at 597 nm (⁴G_5/2→⁶H_7/9), presenting strong orange-red luminescence. NBT-0.04CT∶0.010Sm³⁺ ceramics shows optimal luminescence performances among the Sm³⁺-doped NBT-0.04CT ceramics, and superior thermal stability of its luminous properties is achieved in the temperature range from 278 K to 473 K. The results indicate that NBT-0.04CT∶xSm³⁺ceramics have promising applications in white LED.

6H to 3C Polytypic Transformation in SiC Ceramics During Brazing Process

SHI Haojiang, ZHANG Ruiqian, LI Ming, YAN Jiazhen, LIU Zihao, BAI Dong

2023, 52(8):  1516-1522. 

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In this paper, pure Ni foil was used as an intermediate layer to achieve brazing connection of 6H-SiC at 1 100~1 245 ℃. The microstructure of the brazed joint and the interface between the brazed joint and the 6H-SiC substrate were studied to investigate the effect of brazing process on the crystal structure of SiC ceramics and provide theoretical and experimental data supports for brazing process design. The results show that a small amount of Ni atoms diffuse into the 6H-SiC ceramics during the brazing process and exist in solid solution form, which reduces the dislocation energy of 6H-SiC. The residual stress at the 6H-SiC/brazed joint interface increases with the increase of brazing temperature, and when the brazing temperature reaches 1 245 ℃, the (0001) plane of 6H-SiC at the interface slips along the 1/3 <1100> direction, and the 6H-SiC is sheared to form 3C-SiC. Therefore, SiC ceramics can undergo phase transformation under the influence of stress and brazing material composition during the brazing process, and the effect of brazing process on their crystal structure and properties should be considered for SiC ceramics used in special environments.

Preparation Process and Performance of Thin Film Thermopile (Cu/Cu55Ni45) Heat Flux Sensor

FENG Nanming, DAI Bo, WANG Yong, LI Wei

2023, 52(8):  1523-1531. 

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In this work, Cu and Cu55Ni45 thin films with a thickness of 600 nm were firstly deposited on single crystal Si and Al₂O₃ ceramic substrates by magnetron sputtering respectively. Then, the thin film thermopiles composed of 200 pairs of in-series thermocouples were fabricated by microfabrication technology in 10 mm×10 mm substrate area. Finally, aluminum oxide layers were deposited by reactive magnetron sputtering as thermal resistance layers, with the help of hard mask. The different thickness of the aluminum oxide layer produces the cold and hot ends in the thin film thermopile, giving rise to a voltage under the irradiation of heat flux by the Seebeck effect, realizing the measurement of heat flux. The thin film thermopiles were analyzed and calibrated. The results show that in the Cu/Cu55Ni45 thermopiles deposited on the Si substrate and Al₂O₃ ceramic substrate, the roughness of the Cu films are 20 and 60 nm, the roughness of Cu55Ni45 films are 15 and 20 nm, the electrical resistance of thermopiles are 38.2 Ω and 2.83 kΩ, the sensitivity of thermopiles are 0.069 45 and 0.026 97 mV/(kW·m^-2), respectively. The surface roughness of Cu/Cu55Ni45 thermopiles deposited on single crystal Si substrate and Al₂O₃ ceramic substrate with different surface roughness will be affected, resulting in the difference in electrical resistance of thin film thermopile. In addition, the output thermoelectric voltage exhibits a good linear relationship with heat flux.

Synthesis of Magnetized Hydroxyapatite Whisker and Its Magnetic Response Behavior Under Magnetic Field

CHUAN Dingze, YAN Tingting, LIU Jitao

2023, 52(8):  1532-1539. 

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The orientation of hydroxyapatite whiskers (HAw) is one of key to design and develop bioactive ceramics for bone regeneraction. Guided behavior based on the construction of magnetic anisotropy. In this study, magnetic nanoparticles Fe₃O₄ were loaded onto the surface of HAw by hydrothermal method, and magnetic HAw composites with excellent magnetic response characteristics were successfully prepared. The physicochemical properties and biological properties of magnetized HAw were systematically studied, and its orientation behavior in weak magnetic field was explored. The results show that ferric oxide (Fe₃O₄) nanoparticles are successfully loaded onto the surface of HAw, and the magnetized HAw has superparamagnetism and good magnetic response at room temperature, which can be manupulated by conventional permanent magnets. The alignment direction applied by the external magnetic field is effectively fixed by combining the magnetic field-induced grouting molding technology.The results of CCK-8 experiment show that magnetized HAw has no cytotoxicity.

Preparation and Stress Analysis of As₄₀Se₆₀ Chalcogenide Glass Substrate Films

ZHOU Shenmin, ZHANG Yu

2023, 52(8):  1540-1547. 

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Chalcogenide glass is an excellent infrared optical lens material, but its thermal expansion coefficient is large. Compared with Si, Ge and other infrared optical materials, the chalcogenide glass lens produces larger residual stress in the coating process, and the shape changes after coating is large. The mechanical properties of the film can be improved by studying the stress in the film and optimizing the stress control method. In this paper, the residual stresses of different material coatings on the substrate were studied by measuring the variation of the substrate before and after coating on As₄₀Se₆₀ chalcogenide glass. At the same time, the thermal stress of As₄₀Se₆₀/ZnS/Ge/ZnS/Ge/ZnS/YbF₃/ZnS infrared optical lens film chalcogenide was calculated and simulated by ANSYS software, which verified the rationality of the model. The axial and radial distributions of thermal stress in the film structure were analyzed. The results show that the thermal stress of the film structure is mainly concentrated in the film in the axial direction, and the thermal stress of the surface film is the largest. In the radial direction, the thermal stress is evenly distributed and suddenly drops at the edge. The relationships between thermal stress of the outermost protective film and deposition temperature, adjacent film layer, non-adjacent film layer and substrate were analyzed. The results show that the thermal stress of the protective film is proportional to the deposition temperature in the range of 110 ℃ to 200 ℃. The thickness and material of adjacent and non-adjacent films do not affect the thermal stress of the protective film. The thickness of the base will affect the thermal stress of the protective film.