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70 results on '"Cheng, Zhen-Xiang"'

1. Significant magneto-dielectric effect in SrNd2Fe2O7 at room temperature

Author

Chen, Li-Da, primary, Shu, Li-Huai, additional, Zhang, Bi Hui, additional, Liu, Lin, additional, Lei, Lin, additional, Shao, Ye, additional, Huang, Feng-Zhen, additional, Lv, Yang-Yang, additional, Cheng, Zhen-Xiang, additional, Wang, Jian-Li, additional, Stewart, G. A., additional, Cadogan, J. M., additional, Hutchison, W. D., additional, Zhou, Jian, additional, Liu, Xiao Qiang, additional, Yao, Shu-Hua, additional, Chen, Y. B., additional, and Chen, Yan-Feng, additional

Published
2023
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2. Atomically Dispersed Dual‐Site Cathode with a Record High Sulfur Mass Loading for High‐Performance Room‐Temperature Sodium–Sulfur Batteries

Author

Zhang, Bin‐Wei, primary, Cao, Liuyue, additional, Tang, Cheng, additional, Tan, Chunhui, additional, Cheng, Ningyan, additional, Lai, Wei‐Hong, additional, Wang, Yun‐Xiao, additional, Cheng, Zhen‐Xiang, additional, Dong, Juncai, additional, Kong, Yuan, additional, Dou, Shi‐Xue, additional, and Zhao, Shenlong, additional

Published
2022
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3. Significant magneto-dielectric effect in SrNd2Fe2O7 at room temperature.

Author

Chen, Li-Da, Shu, Li-Huai, Zhang, Bi Hui, Liu, Lin, Lei, Lin, Shao, Ye, Huang, Feng-Zhen, Lv, Yang-Yang, Cheng, Zhen-Xiang, Wang, Jian-Li, Stewart, G. A., Cadogan, J. M., Hutchison, W. D., Zhou, Jian, Liu, Xiao Qiang, Yao, Shu-Hua, Chen, Y. B., and Chen, Yan-Feng

Subjects
SINGLE crystals, MAGNETIC properties, MAGNETIC fields, CRYSTAL structure, ANTIFERROMAGNETISM
Abstract

Here, we report the growth of (Sr, Ca) Nd2Fe2O7 single crystals with the Ruddlesden–Popper structure using an optical floating-zone method. A significantly anisotropic magneto-dielectric effect (MD), ab-plane and c-axial MD coefficients reaching −12.3% and −8.4% measured at 103 Hz in a 1 T magnetic field, can be obtained in a SrNd2Fe2O7 crystal at room temperature. The corresponding anisotropic MD ratio can be reached as high as 1.46. With an increase in the Ca concentration, the MD effect decreases dramatically and is eventually completely suppressed in both directions. Analysis of magnetic properties and 57Fe Mössbauer spectra suggests that the anisotropic MD effects in SrNd2Fe2O7 can be attributed to polaronic hopping between two neighboring Fe3+ ions through oxygen vacancies in an anisotropically antiferromagnetic matrix; the disappearance of the MD effect in Ca-doped SrNd2Fe2O7 is a consequence of the suppression of the antiferromagnetism. Our work suggests that the significantly anisotropic MD effect in SrNd2Fe2O7 crystals at room temperature can be used in magneto-dielectric controlled devices. [ABSTRACT FROM AUTHOR]

Published
2023
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5. Magnetic Field Tuning of Magnetic- and Structure-Phase Transition in Mn2V2O7 Crystals

Author

Chen, Li-Da, primary, Shu, Li-Huai, additional, Liu, Gan, additional, Nie, Pan, additional, Shao, Ye, additional, Luo, Ye-Cheng, additional, Lv, Yang-Yang, additional, Lu, Hao-Min, additional, Zhu, Zeng-Wei, additional, Xi, Xiao-Xiang, additional, Zhou, Jian, additional, Huang, Feng-Zhen, additional, Cheng, Zhen-Xiang, additional, Yao, Shu-Hua, additional, Chen, Y. B., additional, and Chen, Yan-Feng, additional

Published
2022
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14. Crystal growth, thermal and optical properties of SmCa4O(BO3)3 crystal

Author

Yang Hua, Liu Xuesong, Chen Huanchu, Cheng Zhen-Xiang, and Zhang Shu-Jun

Subjects
Analytical chemistry, Crystal growth, Condensed Matter Physics, Thermal expansion, Inorganic Chemistry, Crystal, chemistry.chemical_compound, chemistry, Materials Chemistry, Anisotropy, Single crystal, Calcium borate, Refractive index, Powder diffraction, Nuclear chemistry
Abstract

Oxoborate crystal SmCa 4 O(BO 3 ) 3 (SmCOB) has been grown by the Czochralski (CZ) method for the first time. The X-ray powder diffraction (XRPD) of sintered material and single crystal were performed at room temperature. The DSC experiment showed that SmCOB melts congruently at 1397°C. The data of thermal expansion coefficients along X , Y and Z direction have been measured to be 1.03×10 −5 , 3.8×10 −6 and 8.2×10 −6 K −1 , respectively. The specific heat of the crystal as been measured to be 66 cal/mol K at 300 K. The linear optical properties of SmCOB crystal are reported. The measured transmittance spectra from 400 to 2600 nm showed that the crystal has strong absorption peaks which are anisotropic along different crystallophysic axes in the range of 900–1700 nm.

Published
2000

15. Studies on the growth and defects of GdCa4O(BO3)3 crystals

Author

Zhou Guang-Yong, Han Jian-Ru, Zhang Jiguo, Zhang Shu-Jun, Cheng Zhen-Xiang, and Chen Huanchu

Subjects
Condensed matter physics, Nucleation, Nonlinear optics, Crystal growth, Condensed Matter Physics, law.invention, Inorganic Chemistry, Crystal, chemistry.chemical_compound, Crystallography, Optical microscope, chemistry, law, Materials Chemistry, Macle, Crystal twinning, Calcium borate
Abstract

New nonlinear optical crystals GdCa4O(BO3)3 grown by the Czochralski method in a platinum crucible under air atmosphere are reported in this paper. The growth mechanism is a typical two-dimensional nucleation layer growth. The twin and inclusion defects of this crystal are observed using optical microscopy. The incidence of twinning is in good agreement with Hurle's model. The approaches to reduce and eliminate the defects are presented.

Published
1999

21. Crystallization, phase evolution and ferroelectric properties of sol–gel-synthesized Ba(Ti0.8Zr0.2)O3–x(Ba0.7Ca0.3)TiO3thin films

Author

Wang, Zeng-mei, primary, Zhao, Kuan, additional, Guo, Xin-li, additional, Sun, Wei, additional, Jiang, Hua-long, additional, Han, Xue-qin, additional, Tao, Xu-tang, additional, Cheng, Zhen-xiang, additional, Zhao, Hong-yang, additional, Kimura, Hideo, additional, Yuan, Guo-liang, additional, Yin, Jiang, additional, and Liu, Zhi-guo, additional

Published
2013
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24. Cobalt-doped cadmium selenide colloidal nanowires

Author

Li, Zhen, primary, Du, Ai Jun, additional, Sun, Qiao, additional, Aljada, Muhsen, additional, Cheng, Li Na, additional, Riley, Mark J., additional, Zhu, Zhong Hua, additional, Cheng, Zhen Xiang, additional, Wang, Xiao Lin, additional, Hall, Jeremy, additional, Krausz, Elmars, additional, Qiao, Shi Zhang, additional, Smith, Sean C., additional, and Lu, Gao Qing (Max), additional

Published
2011
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25. Ultrafast spectroscopy of the Mn3+ dd transition in YMnO3 film

Author

Zhang Zheng-Bing, Ma Guo-Hong, Xu Yue, Lin Xian, Li Gao-Fang, Cheng Zhen-Xiang, and Jin Zuan-Ming

Subjects
Condensed Matter::Materials Science, Materials science, Chemical physics, General Physics and Astronomy, Condensed Matter::Strongly Correlated Electrons, Spectroscopy, Ultrashort pulse
Abstract

Photoinduced carrier dynamic behavior of the Mn3+ 3d resonance excitation of YMnO3 thin film is studied by the femtosecond time resolved spectroscopy. The photon energy of the pump pulse is tuned to 1.70 eV, which is corresponding to the Mn3+ 3d energy level at room temperature. With resonant excitation, the transient transmission signals at the zero-delay time gradually increase with temperature increasing. The temperature dependent transmission change results from the blue shift of the Mn3+ 3d energy level, which is believed to originate from the short-range antiferromagnetic order in YMnO3 film. In addition, the fast and slow relaxations of the transient signal arise from electronic-phonon and phonon-spin interactions, respectively. When the temperature is lower than TN, the relaxation time of the fast process increases significantly, which indicates that the strength of electronic-phonon coupling is restrained by the long-range antiferromagnetic order.

Published
2012

29. Growth and Second-Harmonic Generation Properties of Tm 3+ , Yb 3+ , Bi 3+ and Li + Doped GdCa 4 O(BO 3 ) 3 Crystals

Author

Zhang Shu-Jun, Chen Huanchu, Cheng Zhen-Xiang, Wang Ji-Yang, Liu Jun-Hai, Han Jian-Ru, and Zhang Shaojun

Subjects
Crystal, Materials science, Optics, business.industry, Doping, Analytical chemistry, General Physics and Astronomy, Second-harmonic generation, business, Ion
Abstract

The rare-earth ions (Yb3+, Tm3+) and Li+, Bi3+ ions doped GdCa4O(BO3)3 crystals were grown using the Czochralski pulling method. The second-harmonic generation conversion efficiencies of the GdCOB:Yb and GdCOB:Tm crystals are 31.3% and 33.3%, respectively, while the undoped GdCOB crystal is 27.9%. The conversion efficiencies of Yb3+, Tm3+ doped GdCOB are improved by 12% and 19%, respectively, compared to that of the undoped one. The conversion efficiencies of Li+, Bi3+ doped GdCOB crystals are 33% and 38.3%, which are improved by 15% and 37% as compared to that of the undoped crystal. The results are discussed using the anion group theory.

Published
2001

30. Effect of Strontium Ion on the Growth and Second-Harmonic Generation Properties of GdCa 4 O(BO 3 ) 3 Crystal

Author

Shao Zong-Shu, Cheng Zhen-Xiang, Han Jian-Ru, Liu Jun-Hai, Wang Ji-Yang, Zhang Shu-Jun, and Chen Huanchu

Subjects
Materials science, Laser diode, business.industry, Slope efficiency, Energy conversion efficiency, Analytical chemistry, General Physics and Astronomy, Second-harmonic generation, Laser, Ion, law.invention, Crystal, Optics, law, business, Powder diffraction
Abstract

Large sized and optical quality GdCa4O(BO3)3 (GdCOB) crystal with calcium partially substituted by strontium (Sr) ions was grown for the first time. The x-ray powder diffraction shows that the Sr ion has an effect on the cell parameters of the GdCOB crystal. Second-harmonic generation (SHG) experiments were performed on the Sr:GdCOB and GdCOB crystals along the spatial phase-matching direction. The results show that the cw green laser output power is 1.04 W when the laser diode pump power is 10 W in the Nd:YVO4/Sr:GdCOB intracavity laser. Considering the slope efficiency of Nd:YVO4 and the fundamental laser in cavity, the intracavity SHG conversion efficiency of the GdCOB crystal is 21% while it is 24% for the Sr:GdCOB crystal, the SHG conversion efficiency is improved by 14%. The effect of the Sr ions on the nonlinearity of the GdCOB crystal is also discussed by using the anion group theory. PACS: 42. 65. Ky, 78. 20. -e, 78. 55. Hx

Published
2000

31. An Investigation of the Nanomechanical Properties of 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 Thin Films.

Author

Cai, Zhong‐Lan, Wang, Zeng‐Mei, Wang, Huan‐Huan, Cheng, Zhen‐Xiang, Li, Bao‐Wen, Guo, Xin‐Li, Kimura, Hideo, Kasahara, Akira, and Landis, C. M.

Subjects
BARIUM titanate, METALLIC thin films, NANOELECTROMECHANICAL systems, PIEZOELECTRICITY, MECHANICAL properties of metals, CRYSTAL morphology
Abstract

For practical application, the functional piezoelectric film in microelectromechanical systems should meet the requirement of physical properties, as well as the mechanical properties. In this article, 0.5 Ba( Ti0.8 Zr0.2) O3-0.5( Ba0.7 Ca0.3) TiO3 (0.5 BZT-0.5 BCT) thin films with varied properties were prepared on (100) Si substrates via a sol-gel technique at different annealing temperatures. The effects of the annealing temperature on the morphology, piezoelectricity, hardness, and elastic modulus were studied. Particular attention was paid to the surface frictional behavior of films, and the changes in the friction force can be radically explained in terms of differences in the hardness/elastic modulus ratio and the residual stress of films. And, it reveals that the higher ratio of hardness to elastic modulus and tensile residual stress can contribute to a lower friction force for 0.5 BZT-0.5 BCT film during sling friction. [ABSTRACT FROM AUTHOR]

Published
2015
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35. Upconversion luminescence and Spectra characteristics of Er3+, Tm3+ co-doped NaY(WO4)2 crystal

Author

Shang Mei-Ru, Fu Bo, Tan Hao, Cheng Zhen-Xiang, Su Jing, Zhang Guang-Yin, Song Feng, and Chen Huan-Chu

Subjects
Materials science, Absorption spectroscopy, business.industry, Upconversion luminescence, Doping, Excitation spectra, Analytical chemistry, General Physics and Astronomy, Spectral line, Crystal, Optics, Emission spectrum, business, Co doped
Abstract

Absorption spectra, emission spectra, excitation spectra, and upconversion luminescence of Er 3+ , Tm 3+ co-doped NaY(WO 4 ) 2 crystal were measured at room temperature. Intensity parameters are calculated from absorption spectra in terms of Judd-Offelt theory. Transition processes of the energy levels of Er 3+ and Tm 3+ were analyzed in details and the cross relaxations: 1 G 4 (Tm 3+ )＋ 4 I 15/2 (Er 3+ )→ 3 F 4 (Tm 3+ ) + 4 F 9/2 (Er 3+ ) , 1 G 4 (Tm 3+ )＋ 4 I 15/2 (Er 3+ )→ 3 H 5 (Tm 3+ )＋ 4 I 9/2 (Er 3+ ), 3 F 4 (Tm 3+ )＋ 4 I 9/2 (Er 3+ )→ 3 H 6 (Tm 3+ )＋ 4 S 3/2 or 2 H 11/2 (Er 3+ ) and 4 F 9/2 (Er 3+ )＋ 3 H 6 (Tm 3+ )→ 4 I 15/2 (Er 3+ )+ 3 F 3 (Tm 3+ ) were put forward. Sufficient proofs have been found to illustrate the use of Er 3+ as a sensitizer which is effective for the Tm 3+ -doped crystal.

Published
2004

36. Spectroscopic properties of Tm3+-doped NaY (WO4)2 crystals

Author

Zhang Guang-Yin, Song Feng, Chen Huan-Chu, Wu Zhao-Hui, Tan Hao, Cheng Zhen-Xiang, Tian Jian-Guo, Su Jing, and Shang Mei-Ru

Subjects
Materials science, Doping, General Physics and Astronomy, Physical chemistry
Abstract

Z_scan experiments are performed on the azobenzene polymer (DR_13_PMMA) films with He_Ne laser. It is found that the relation between the cha nge of refractive index of the sample and the light intensity behaves like a sat u rable effect, whose relative parameters are alterable with light intensity. It i s also found that the change of refractive index induced by linearly polarized l ight is distinctly greater than that induced by circularly polarized light. The phenomena are explained by using the theory based on the effect of angular hole burning of photoisomerization.

Published
2004

43. Enhancement of ferromagnetic and dielectric properties in lanthanum doped BiFeO3 by hydrothermal synthesis

Author

Du, Yi, Cheng, Zhen Xiang, Shahbazi, Mahboobeh, Collings, Edward W., Dou, Shi Xue, and Wang, Xiao Lin

Subjects
*FERRITES, *ELECTRIC properties of metals, *FERROMAGNETISM, *PERMITTIVITY, *LANTHANUM, *PEROVSKITE, *MOLECULAR structure, *X-ray diffraction
Abstract

Abstract: Multiferroic Bi1−x La x FeO3 (x =0.0, 0.1, 0.2, and 0.3) micro-particles were successfully synthesized by a hydrothermal technique. All the samples were phase pure crystallizing in a perovskite structure with a space group of R3c. XRD refinement revealed that the lattice parameters increased along with increase of La content, while the Fe–O octahedra became more distorted. It was found that the morphologies of as-obtained micron-sized particles turned from spheroidal to octahedral according to different doping levels. The dielectric constant of Bi1−x La x FeO3 sample increased after La doping, and reached the largest value for the sample of x =0.2, both in low and high frequency range at room temperature. All the as-prepared samples exhibited magnetic moments starting above room temperature. It was found that the magnetic moment was significantly enhanced from 0.264emu/g of BiFeO3 to 0.658emu/g of Bi0.9La0.1FeO3 in a field of 3T at 77K. Both enhancements of ferromagnetic and dielectric properties possibly attribute to the changes of lattice parameters and Fe–O bond lengths caused by lanthanum substitution. [Copyright &y& Elsevier]

Published
2010
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44. Planar waveguide fabrication and refractive index characterization in Er:NaY(WO4)2 crystal by MeV silicon ion implantation

Author

Chen, Feng, Cheng, Zhen-Xiang, Wang, Xue-Lin, Wang, Ke-Ming, Chen, Huan-Chu, Lu, Qing-Ming, and Shen, Ding-Yu

Subjects
*CRYSTALS, *IONS
Abstract

A planar waveguide was formed in Er:NaY(WO4)2 crystal by the implantation of 3.0 MeV Si+ ions at a dose of 2×1015 ions/cm2 at room temperature. The prism-coupling method was used to observe the dark modes of the waveguide. Both TE- and TM-polarized light were carried out to measure the effective refractive index of the modes. Refractivity calculation method (RCM) was used to reconstruct the profiles of the refractive index in the waveguide. Moreover, the lattice disorder and the ionization damage of 3.0 MeV Si in Er:NaY(WO4)2 were obtained by using the simulation of TRIM''98 (transport of ions in matter) code. [Copyright &y& Elsevier]

Published
2002
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47. Crystallization, phase evolution and ferroelectric properties of sol–gel-synthesized Ba(Ti0.8Zr0.2)O3–x(Ba0.7Ca0.3)TiO3thin films

Author

Wang, Zeng-mei, Zhao, Kuan, Guo, Xin-li, Sun, Wei, Jiang, Hua-long, Han, Xue-qin, Tao, Xu-tang, Cheng, Zhen-xiang, Zhao, Hong-yang, Kimura, Hideo, Yuan, Guo-liang, Yin, Jiang, and Liu, Zhi-guo

Abstract

A lead-free piezoelectric material with ultra-high properties, Ba(Ti0.8Zr0.2)O3–x(Ba0.7Ca0.3)TiO3(BZT–xBCT) nanocrystals was synthesized viaa sol–gel method, and the corresponding thin films were also deposited on Pt/Ti/SiO2/Si substrates by a spin-coating approach. The BZT–xBCT thin film exhibited a high remnant polarization of 22.15 μC cm−2with a large coercive field of 68.06 kV cm−1. The resultant gel is calcined at various elevated temperatures and studied with FTIR/XRD/Raman/DSC-TGA/AFM/SEM techniques for gel composition, crystallization, phase transition, thermochemistry and the morphology of the film. Although the room temperature crystal structure of the BZT–xBCT nanocrystals appears to be a standard perovskite structure by conventional X-ray diffraction (XRD), Raman spectroscopy demonstrates the presence of non-centrosymmetric regions arising from the off-centering of the titanium (zirconium) atoms. The Raman spectra findings demonstrate the degree by which the tetragonal phase grows with the increase of calcining temperature in BZT–0.5BCT, and the characteristic ferroelectric–ferroelectric phase transition in BZT–xBCT while going through the MPB process. The structural and constituent evolution for the conversion process from gel to ceramic, as well as the formation mechanism of the BZT–0.5BCT crystallite, were also elucidated.

Published
2012
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48. Analysis of optical waveguide formation in Er:NaY(WO4)2crystal by MeV He+ion implantation

Author

Cheng, Zhen-Xiang, Zhang, Shujun, Yi, Xiujie, Chen, Feng, Han, Jianru, and Chen, Huanchu

Abstract

Tetragonal scheelite-like single crystals Er:NaY(WO4)2(Er:NYW) have been grown along its 〈101〉direction by using RF-heating Czochralski (CZ) method. A planar optical waveguide in the as-grown Er:NaY(WO4)2crystal was formed by 2.6 MeV He+ions implantation with dose of 1.5×1016ions/cm2at room temperature. Using the prism coupling technique, the dark modes were measured: four TE modes and five TM modes were observed in the waveguide. Using the reflectivity calculation method (RCM), the refractive index profiles were reconstructed and analyzed before and after the optical waveguide was annealed at 300 °C for 30 min. The energy loss was simulated by the transport of ions in matter (TRIM) code, and the results were investigated in comparison with the refractive index profile in the waveguide.

Published
2002
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50. Enhancement of magnetization and dielectric properties of chromium-doped BiFeO3 with tunable morphologies

Author

Du, Yi, Cheng, Zhen Xiang, Dou, Shi Xue, Shahbazi, Mahboobeh, and Wang, Xiao Lin

Subjects
*BISMUTH compounds, *FERRITES, *CHROMIUM, *ELECTRIC properties of metals, *MAGNETIZATION, *RIETVELD refinement, *CHEMICAL bonds, *X-ray diffraction
Abstract

Abstract: Multiferroic BiFe1 − x Cr x O3 (x =0.025, 0.05, 0.075, and 0.1) is prepared by the hydrothermal method. Samples are systematically characterized by X-ray diffraction, Rietveld refinement, SEM, dielectric and magnetic measurements. It is found that the lattice parameters, the morphology and the size of the obtained particles strongly depend on the Cr doping level. The lattice parameters a and c and the Fe–O (1) bond lengths decrease, while the Fe–O (2) bond lengths increase, as x values rise from 0.025 to 0.1. The particle morphology changes from spherical shape for pure BiFeO3 to octahedral shape for x =0.1. The dielectric constant and the magnetization increase greatly with the increase of the Cr doping level. Both the M–T and the M–H results reveal that the Cr doping enhances the ferromagnetic state in the doped BiFeO3. The possible reasons for the enhanced magnetic and dielectric properties are discussed briefly. [ABSTRACT FROM AUTHOR]

Published
2010
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