• Characterization of microwave and terahertz dielectric properties of single crystal La2Ti2O7 along one single direction

      Zhang, Man; orcid: 0000-0002-1094-7279; Tang, Zhiyong; orcid: 0000-0002-1921-6034; Zhang, Hangfeng; Smith, Graham; orcid: 0000-0003-3273-7085; Jiang, Qinghui; Saunders, Theo; orcid: 0000-0003-4250-3071; Yang, Bin; Yan, Haixue; orcid: 0000-0002-4563-1100
      New generation wireless communication systems require characterisations of dielectric permittivity and loss tangent at microwave and terahertz bands. La2Ti2O7 is a candidate material for microwave application. However, all the reported microwave dielectric data are average value from different directions of a single crystal, which could not reflect its anisotropic nature due to the layered crystal structure. Its dielectric properties at the microwave and terahertz bands in a single crystallographic direction have rarely been reported. In this work, a single crystal ferroelectric La2Ti2O7 was prepared by floating zone method and its dielectric properties were characterized from 1 kHz to 1 THz along one single direction. The decrease in dielectric permittivity with increasing frequency is related to dielectric relaxation from radio frequency to microwave then to terahertz band. The capability of characterizing anisotropic dielectric properties of a single crystal in this work opens the feasibility for its microwave and terahertz applications.
    • Characterization of microwave and terahertz dielectric properties of single crystal La2Ti2O7 along one single direction

      Zhang, Man; orcid: 0000-0002-1094-7279; Tang, Zhiyong; orcid: 0000-0002-1921-6034; Zhang, Hangfeng; Smith, Graham; orcid: 0000-0003-3273-7085; Jiang, Qinghui; Saunders, Theo; orcid: 0000-0003-4250-3071; Yang, Bin; Yan, Haixue; orcid: 0000-0002-4563-1100 (Elsevier, 2021-08-27)
      New generation wireless communication systems require characterisations of dielectric permittivity and loss tangent at microwave and terahertz bands. La2Ti2O7 is a candidate material for microwave application. However, all the reported microwave dielectric data are average value from different directions of a single crystal, which could not reflect its anisotropic nature due to the layered crystal structure. Its dielectric properties at the microwave and terahertz bands in a single crystallographic direction have rarely been reported. In this work, a single crystal ferroelectric La2Ti2O7 was prepared by floating zone method and its dielectric properties were characterized from 1 kHz to 1 THz along one single direction. The decrease in dielectric permittivity with increasing frequency is related to dielectric relaxation from radio frequency to microwave then to terahertz band. The capability of characterizing anisotropic dielectric properties of a single crystal in this work opens the feasibility for its microwave and terahertz applications.
    • Millimeter-wave free-space dielectric characterization

      Liu, Xiaoming; Gan, Lu; Yang, Bin (Elsevier, 2021-05-12)
      Millimeter wave technologies have widespread applications, for which dielectric permittivity is a fundamental parameter. The non-resonant free-space measurement techniques for dielectric permittivity using vector network analysis in the millimeter wave range are reviewed. An introductory look at the applications, significance, and properties of dielectric permittivity in the millimeter wave range is addressed first. The principal aspects of free-space millimeter wave measurement methods are then discussed, by assessing a variety of systems, theoretical models, extraction algorithms and calibration methods. In addition to conventional solid dielectric materials, the measurement of artificial metamaterials, liquid, and gaseous-phased samples are separately investigated. The pros of free-space material extraction methods are then compared with resonance and transmission line methods, and their future perspective is presented in the concluding part.
    • Millimeter-Wave Free-Space Dielectric Characterization

      Liu, Xiaoming; Gan, Lu; Yang, Bin
      Millimeter wave technologies have widespread applications, for which dielectric permittivity is a fundamental parameter. The non-resonant free-space measurement techniques for dielectric permittivity using vector network analysis in the millimeter wave range are reviewed. An introductory look at the applications, significance, and properties of dielectric permittivity in the millimeter wave range is addressed first. The principal aspects of free-space millimeter wave measurement methods are then discussed, by assessing a variety of systems, theoretical models, extraction algorithms and calibration methods. In addition to conventional solid dielectric materials, the measurement of artificial metamaterials, liquid, and gaseous-phased samples are separately investigated. The pros of free-space material extraction methods are then compared with resonance and transmission line methods, and their future perspective is presented in the concluding part.
    • Probing NaCl hydrate formation from aqueous solutions by terahertz time-domain spectroscopy

      Chen, Ligang; orcid: 0000-0002-4231-8821; Ren, Guanhua; Liu, Liyuan; orcid: 0000-0002-7050-3792; Guo, Pan; Wang, Endong; Zhu, Zhongjie; Yang, Jinrong; Shen, Jianxiong; Zhang, Zongchang; Zhou, Lu; et al. (Royal Society of Chemistry (RSC), 2020)
      The cooling-induced formation of a hydrate in aqueous NaCl solutions was probed using terahertz time-domain spectroscopy (THz-TDS).
    • Terahertz Characterization of Lead-Free Dielectrics for Different Applications

      Zhang, Man; Zhang, Hangfeng; Jiang, Qinghui; orcid: 0000-0001-7851-2653; Gao, Feng; orcid: 0000-0002-5075-4076; Chen, Riqing; Zhang, Dou; orcid: 0000-0001-8555-2784; Reece, Michael John; orcid: 0000-0002-2293-7123; Yang, Bin; Viola, Giuseppe; Yan, Haixue; orcid: 0000-0002-4563-1100 (American Chemical Society (ACS), 2021-11-02)
    • Terahertz Characterization of Lead-Free Dielectrics for Different Applications

      Zhang, Man; Zhang, Hangfeng; Jiang, Qinghui; orcid: 0000-0001-7851-2653; Gao, Feng; orcid: 0000-0002-5075-4076; Chen, Riqing; Zhang, Dou; orcid: 0000-0001-8555-2784; Reece, Michael John; orcid: 0000-0002-2293-7123; Yang, Bin; Viola, Giuseppe; Yan, Haixue; orcid: 0000-0002-4563-1100 (American Chemical Society (ACS), 2021-11-02)
    • Terahertz Characterization of Lead-Free Dielectrics for Different Applications.

      Zhang, Man; Zhang, Hangfeng; Jiang, Qinghui; orcid: 0000-0001-7851-2653; Gao, Feng; orcid: 0000-0002-5075-4076; Chen, Riqing; Zhang, Dou; orcid: 0000-0001-8555-2784; Reece, Michael John; orcid: 0000-0002-2293-7123; Yang, Bin; Viola, Giuseppe; Yan, Haixue; orcid: 0000-0002-4563-1100 (2021-11-02)
      In this spotlight on applications, we describe our recent progress on the terahertz (THz) characterization of linear and nonlinear dielectrics for broadening their applications in different electrical devices. We begin with a discussion on the behavior of dielectrics over a broadband of frequencies and describe the main characteristics of ferroelectrics, as they are an important category of nonlinear dielectrics. We then move on to look at the influence of point defects, porosities, and interfaces, including grain boundaries and domain walls, on the dielectric properties at THz frequencies. Based on our studies on linear dielectrics, we show that THz characterization is able to probe the effect of porosities, point defects, shear planes, and grain boundaries to improve dielectric properties for telecommunication applications. Further, we demonstrate that THz measurements on relaxor ferroelectrics can be successfully used to study the reversibility of the electric field-induced phase transitions, providing guidance for improving their energy storage efficiency in capacitors. Finally, we show that THz characterization can be used to characterize the effect of domain walls in ferroelectrics. In particular, our studies indicate that the dipoles located within domain walls provide a lower contribution to the permittivity at THz frequencies than the dipoles present in domains. The new findings could help develop a new memory device based on nondestructive reading operations using a THz beam.
    • Terahertz Reading of Ferroelectric Domain Wall Dielectric Switching

      Zhang, Man; Chen, Zhe; Yue, Yajun; Chen, Tao; Yan, Zhongna; Jiang, Qinghui; Yang, Bin; Eriksson, Mirva; Tang, Jianhua; Zhang, Dou; orcid: 0000-0001-8555-2784; et al. (American Chemical Society (ACS), 2021-03-09)
    • Terahertz Signatures of Hydrate Formation in Alkali Halide Solutions

      Chen, Ligang; Ren, Guanhua; Liu, Liyuan; orcid: 0000-0002-7050-3792; Guo, Pan; Wang, Endong; Zhou, Lu; Zhu, Zhongjie; Zhang, Jianbing; Yang, Bin; Zhang, Wentao; et al. (American Chemical Society (ACS), 2020-08-06)
    • Ultrafast Electric Field-Induced Phase Transition in Bulk Bi0.5Na0.5TiO3 under High-Intensity Terahertz Irradiation

      Zhang, Man; McKinnon, Ruth A.; Viola, Giuseppe; Yang, Bin; Zhang, Dou; orcid: 0000-0001-8555-2784; Reece, Michael J.; orcid: 0000-0002-2293-7123; Abrahams, Isaac; orcid: 0000-0002-8606-6056; Yan, Haixue; orcid: 0000-0002-4563-1100 (American Chemical Society (ACS), 2020-12-10)