Journal of Advanced Dielectrics
Co-Editors-in-Chief
Xi Yao
Bhoopendra Singh, Vivek Pratap, Mohit Katiyar, S. M. Abbas, Y. K. Sharma, A. M. Siddiqui, and N. Eswara Prasad

In this study, carbon black (CB) powder-loaded polyurethane (PU) composites (CB–PU composites) were prepared by melt mixing method with different volume percentages (45, 50, 55, 58 and 61 vol.%) of CB in the PU matrix. The prepared CB–PU composites had been further studied for surface morphology using the field-emission scanning electron microscopy (FESEM) technique. Dielectric properties in terms of real permittivity (𝜀′) and imaginary permittivity (𝜀′′) of the fabricated composites were computed using an Agilent E8364B vector network analyzer in the frequency range of 8–12 GHz (X-band). Dielectric loss factor of the prepared CB–PU composites was computed in terms of the dielectric loss tangent (tan δe = 𝜀′′/𝜀′). Microwave absorbing properties were appraised in terms of the reflection loss (RL) which in turn was calculated for varying thicknesses of the prepared composites from the measured real and imaginary permittivity data. The minimum RL was observed as −20.10 dB for the absorber with a thickness of 2.2 mm and the bandwidth achieved was 1.92 GHz for RL ≤−10 dB. Based on the above results these CB–PU composites have potential use as effective microwave absorbers in 8–12-GHz (X-band) frequency range.In this study, carbon black (CB) powder-loaded polyurethane (PU) composites (CB–PU composites) were prepared by melt mixing method with different volume percentages (45, 50, 55, 58 and 61 vol.%) of CB in the PU matrix. The prepared CB–PU composites had been further studied for surface morphology using the field-emission scanning electron microscopy (FESEM) technique. Dielectric properties in terms of real permittivity (𝜀′) and imaginary permittivity (𝜀′′) of the fabricated composites were computed using an Agilent E8364B vector network analyzer in the frequency range of 8–12 GHz (X-band). Dielectric loss factor of the prepared CB–PU composites was computed in terms of the dielectric loss tangent (tan δe = 𝜀′′/𝜀′). Microwave absorbing properties were appraised in terms of the reflection loss (RL) which in turn was calculated for varying thicknesses of the prepared composites from the measured real and imaginary permittivity data. The minimum RL was observed as −20.10 dB for the absorber with a thickness of 2.2 mm and the bandwidth achieved was 1.92 GHz for RL ≤−10 dB. Based on the above results these CB–PU composites have potential use as effective microwave absorbers in 8–12-GHz (X-band) frequency range.

Jan. 01, 1900
  • Vol. 11 Issue 1 2150001 (2021)
  • S. G. Chavan, A. N. Tarale, and D. J. Salunkhe

    Thin films of polycrystalline (Ba1−xSrx)TiO3 (x = 0.2 and 0.3) with Perovskite structure were prepared by a dip and dry technique on a platinum-coated silicon substrate. The good quality thin films with uniform microstructure and thickness were successfully produced by dip-coating techniques annealed at 730∘C for 1 h. The resulting thin film shows a well-developed dense polycrystalline structure with more uniform grain size distribution. The BST thin films were characterized for their structural, Raman spectroscopy, morphological properties, and complex impedance properties. The dielectric constant-frequency curve showed the good dielectric constant and loss dielectric loss with low-frequency dispersion. The BST 0.3 thin film reveals that the dielectric constant and dielectric loss at a frequency of 1 kHz were 578 and 0.02, respectively. The obtained results on dielectric properties can be analyzed in terms of the Maxwell–Wagner model.Thin films of polycrystalline (Ba1−xSrx)TiO3 (x = 0.2 and 0.3) with Perovskite structure were prepared by a dip and dry technique on a platinum-coated silicon substrate. The good quality thin films with uniform microstructure and thickness were successfully produced by dip-coating techniques annealed at 730∘C for 1 h. The resulting thin film shows a well-developed dense polycrystalline structure with more uniform grain size distribution. The BST thin films were characterized for their structural, Raman spectroscopy, morphological properties, and complex impedance properties. The dielectric constant-frequency curve showed the good dielectric constant and loss dielectric loss with low-frequency dispersion. The BST 0.3 thin film reveals that the dielectric constant and dielectric loss at a frequency of 1 kHz were 578 and 0.02, respectively. The obtained results on dielectric properties can be analyzed in terms of the Maxwell–Wagner model.

    Jan. 01, 1900
  • Vol. 11 Issue 1 2150002 (2021)
  • Aziz Nfissi, Yahya Ababou, Mounir Belhajji, Salaheddine Sayouri, and Taj-dine Lamcharfi

    Structural and dielectric properties of Ce-doped BaTi0.97Y0.03O3 powders, with the chemical formulation (Ba1−xCex)(Ti(0.97−x/4)- Y0.03)O3 such as x = 0%, 1%, 3%, 5%, 7% and 9%, produced by the sol–gel method, have been investigated. X-ray diffraction analysis showed that Ce3+ ions incorporated Ba sites until x= 7% indicating that this concentration represents a solubility limit of Ce3+ ions in BaTi0.97Y0.03O3 matrix. Scanning electron microscopy (SEM) analysis showed a decrease in grain size down to the same concentration of 7%. Raman spectroscopy analysis showed the appearance of A1g mode, which we attributed to the effect of incorporation of Ce3+ and Y3+ in BaTiO3 matrix. Dielectric measurements revealed that doping with cerium lowers the temperature of permittivity maximum at the ferroelectric-to-paraelectric transition (FPT) of the BaTi0.97Y0.03O3 sample, and reaches a value that should be below 40∘C for x= 9%. Moreover, the phenomenon of dielectric resonance was observed on all Ce-doped samples, which was not the case with other dopants as reported in the literature.Structural and dielectric properties of Ce-doped BaTi0.97Y0.03O3 powders, with the chemical formulation (Ba1−xCex)(Ti(0.97−x/4)- Y0.03)O3 such as x = 0%, 1%, 3%, 5%, 7% and 9%, produced by the sol–gel method, have been investigated. X-ray diffraction analysis showed that Ce3+ ions incorporated Ba sites until x= 7% indicating that this concentration represents a solubility limit of Ce3+ ions in BaTi0.97Y0.03O3 matrix. Scanning electron microscopy (SEM) analysis showed a decrease in grain size down to the same concentration of 7%. Raman spectroscopy analysis showed the appearance of A1g mode, which we attributed to the effect of incorporation of Ce3+ and Y3+ in BaTiO3 matrix. Dielectric measurements revealed that doping with cerium lowers the temperature of permittivity maximum at the ferroelectric-to-paraelectric transition (FPT) of the BaTi0.97Y0.03O3 sample, and reaches a value that should be below 40∘C for x= 9%. Moreover, the phenomenon of dielectric resonance was observed on all Ce-doped samples, which was not the case with other dopants as reported in the literature.

    Jan. 01, 1900
  • Vol. 11 Issue 1 2150003 (2021)
  • N. Lyapunov, C. H. Suen, C. M. Wong, Xiaodan Tang, Z. L. Ho, K. Zhou, X. X. Chen, H. M. Liu, Xiaoyuan Zhou, and J. Y. Dai

    The coming Big Data Era requires progress in storage and computing technologies. As an emerging memory technology, Resistive RAM (RRAM) has shown its potential in the next generation high-density storage and neuromorphic computing applications, which extremely demand low switching voltage and power consumption. In this work, a 10 nm-thick amorphous GeS2 thin film was utilized as the functional layer of RRAM in a combination with Ag and Pt electrodes. The structure and memory performance of the GeS2-based RRAM device was characterized — it presents high on/off ratio, fast switching time, ultralow switching voltage (0.15 V) and power consumption (1.0 pJ and 0.56 pJ for PROGRAM and ERASE operations, respectively). We attribute these competitive memory characteristics to Ag doping phenomena and subsequent formation of Ag nano-islands in the functional layer that occurs due to diffusion of Ag from electrode into the GeS2 thin film. These properties enable applications of GeS2 for low energy RRAM device.The coming Big Data Era requires progress in storage and computing technologies. As an emerging memory technology, Resistive RAM (RRAM) has shown its potential in the next generation high-density storage and neuromorphic computing applications, which extremely demand low switching voltage and power consumption. In this work, a 10 nm-thick amorphous GeS2 thin film was utilized as the functional layer of RRAM in a combination with Ag and Pt electrodes. The structure and memory performance of the GeS2-based RRAM device was characterized — it presents high on/off ratio, fast switching time, ultralow switching voltage (0.15 V) and power consumption (1.0 pJ and 0.56 pJ for PROGRAM and ERASE operations, respectively). We attribute these competitive memory characteristics to Ag doping phenomena and subsequent formation of Ag nano-islands in the functional layer that occurs due to diffusion of Ag from electrode into the GeS2 thin film. These properties enable applications of GeS2 for low energy RRAM device.

    Jan. 01, 1900
  • Vol. 11 Issue 1 2150004 (2021)
  • Souad Chkoundali, and Abdelhedi Aydi

    Bis-Tetrapropylammonium tetrabromozincate was synthesized and characterized by X-ray powder diffraction, as well as vibrational and impedance spectroscopy. Rietveld’s refinement of X-ray diffractogram confirmed the crystallization of the compound through the monoclinic system (space group C2/c). A temperature study of Raman scattering revealed two phase transitions at approximately T1 = 340 K and T2 = 393 K. The wavenumber and the line width’s evolution as a function of temperature showed some peculiarities associated with these transitions, which suggests that they are governed by the reorientation of the organic part [N(C3H7)4]+. The complex impedance plotted as a double semicircular arc in the studied temperature range and the centers of these semicircles lie below the real axis, which indicates that the material is an on-Debye type. These semicircular arcs are related to the bulk and the grain boundary effects. Furthermore, the alternating current conductivity of [N(C3H7)4]2ZnBr4 obeyed Jonscher’s law: σAC(ω) = σdc+Aωs and the conduction could be attributed to the correlated barrier hopping (CBH) model in both region(I) and (II) and the Non-overlapping Small Polaron Tunneling (NSPT) in region (III).Bis-Tetrapropylammonium tetrabromozincate was synthesized and characterized by X-ray powder diffraction, as well as vibrational and impedance spectroscopy. Rietveld’s refinement of X-ray diffractogram confirmed the crystallization of the compound through the monoclinic system (space group C2/c). A temperature study of Raman scattering revealed two phase transitions at approximately T1 = 340 K and T2 = 393 K. The wavenumber and the line width’s evolution as a function of temperature showed some peculiarities associated with these transitions, which suggests that they are governed by the reorientation of the organic part [N(C3H7)4]+. The complex impedance plotted as a double semicircular arc in the studied temperature range and the centers of these semicircles lie below the real axis, which indicates that the material is an on-Debye type. These semicircular arcs are related to the bulk and the grain boundary effects. Furthermore, the alternating current conductivity of [N(C3H7)4]2ZnBr4 obeyed Jonscher’s law: σAC(ω) = σdc+Aωs and the conduction could be attributed to the correlated barrier hopping (CBH) model in both region(I) and (II) and the Non-overlapping Small Polaron Tunneling (NSPT) in region (III).

    Jan. 01, 1900
  • Vol. 11 Issue 1 2150005 (2021)
  • D. V. Kuzenko

    The article presents the results of research the pre-transitional features of the behavior of solid solutions based on lead zirconate-titanate. The presence of a “special” critical temperature Td on the temperature dependences of the permittivity 𝜀(T) and the remanent polarization Pr(T), preceding the temperature of the paraelectric phase transition at the Curie temperature TC, is noted. In the temperature range T Td, the Pr(T) dependence obeys a power law. In the temperature range TdTTC, this law is not fulfilled. The results of X-ray experiments make it possible to associate this behavior with reversible disordering at TTd of an ordered domain structure formed during the polarization of piezoelectric ceramics and with its irreversible disordering in the temperature range TdTTC. This is due to the appearance of internal mechanical stresses in a polycrystalline ferroelectric due to irreversible depolarization of the samples at temperatures TdTTC.The article presents the results of research the pre-transitional features of the behavior of solid solutions based on lead zirconate-titanate. The presence of a “special” critical temperature Td on the temperature dependences of the permittivity 𝜀(T) and the remanent polarization Pr(T), preceding the temperature of the paraelectric phase transition at the Curie temperature TC, is noted. In the temperature range T Td, the Pr(T) dependence obeys a power law. In the temperature range TdTTC, this law is not fulfilled. The results of X-ray experiments make it possible to associate this behavior with reversible disordering at TTd of an ordered domain structure formed during the polarization of piezoelectric ceramics and with its irreversible disordering in the temperature range TdTTC. This is due to the appearance of internal mechanical stresses in a polycrystalline ferroelectric due to irreversible depolarization of the samples at temperatures TdTTC.

    Jan. 01, 1900
  • Vol. 11 Issue 1 2150006 (2021)
  • Longhai Yang, Luwen Song, Qi Li, and Tao Zhang

    (YxBi1−x)2/3Cu3Ti4O12 (x= 0.00–0.30) ceramics were successfully prepared via the conventional solid-state method. X-ray powder diffraction confirmed the lattice constant gradually decreases with increasing Y3+ content. SEM images displayed Y3+ substitution for Bi3+ gave rise to the large abnormal grains, and the size of abnormal grains became larger with the increase of Y3+ substitution. (YxBi1−x)2/3Cu3Ti4O12 ceramics presented the relatively high dielectric constant of 7400 with the dielectric loss of 0.055 when x= 0.20. The analysis of complex impedance suggested the grains are semiconductive and the grain boundaries are insulating. For pure Bi2/3Cu3Ti4O12 ceramics, the appearance of additional low-frequency peaks in electrical modulus indicated the grain boundaries are heterogeneous. The investigation of modulus peaks fitting with Arrhenius formula implied that the low-frequency permittivity for all (YxBi1−x)2/3Cu3Ti4O12 ceramics was ascribed to the Maxwell–Wagner relaxation at grain boundaries. In addition, a set of clear dielectric peaks above 200∘C associated with Maxwell–Wagner relaxation can be found for all (YxBi1−x)2/3Cu3Ti4O12 ceramics in the temperature dependence of dielectric constant. This set of clear dielectric peaks showed a tendency to shift to higher temperatures with the increase of Y3+ substitution. Meanwhile, a tiny dielectric anomaly at room temperature was found in Y-doped Bi2/3Cu3Ti4O12 ceramics.(YxBi1−x)2/3Cu3Ti4O12 (x= 0.00–0.30) ceramics were successfully prepared via the conventional solid-state method. X-ray powder diffraction confirmed the lattice constant gradually decreases with increasing Y3+ content. SEM images displayed Y3+ substitution for Bi3+ gave rise to the large abnormal grains, and the size of abnormal grains became larger with the increase of Y3+ substitution. (YxBi1−x)2/3Cu3Ti4O12 ceramics presented the relatively high dielectric constant of 7400 with the dielectric loss of 0.055 when x= 0.20. The analysis of complex impedance suggested the grains are semiconductive and the grain boundaries are insulating. For pure Bi2/3Cu3Ti4O12 ceramics, the appearance of additional low-frequency peaks in electrical modulus indicated the grain boundaries are heterogeneous. The investigation of modulus peaks fitting with Arrhenius formula implied that the low-frequency permittivity for all (YxBi1−x)2/3Cu3Ti4O12 ceramics was ascribed to the Maxwell–Wagner relaxation at grain boundaries. In addition, a set of clear dielectric peaks above 200∘C associated with Maxwell–Wagner relaxation can be found for all (YxBi1−x)2/3Cu3Ti4O12 ceramics in the temperature dependence of dielectric constant. This set of clear dielectric peaks showed a tendency to shift to higher temperatures with the increase of Y3+ substitution. Meanwhile, a tiny dielectric anomaly at room temperature was found in Y-doped Bi2/3Cu3Ti4O12 ceramics.

    Jan. 01, 1900
  • Vol. 11 Issue 1 2150007 (2021)
  • T. Amutha, and K. Jacinth Mispa

    In order to combine the properties of inorganic ion exchanger and conducting organic polymer, a new class of organic–inorganic composite cation exchanger PANI–Ti(IV) phosphosulphosalicylate (PTPSS) was synthesized by intercalating polyaniline (PANI) into Ti(IV) phosphosulphosalicylate (Ti(IV) PSS) using sol–gel chemical route with enhanced properties. PTPSS has been characterized by using Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDAX), thermo gravimetric analysis (TGA-DTG), and Transmission Electron Microscopy (TEM). Ac electrical conductivity studies were also performed. This material possessed electrical conductivity of 10−3 – 10−6Scm−1which falls in the semiconducting range. The frequency (2 × 105 – 1 × 106 Hz) dependent Ac conductivity at room temperature suggests the evidence for the transport mechanism for the conductivity in PTPSS. The structure of the composite cation exchanger extremely supports its conducting behavior.In order to combine the properties of inorganic ion exchanger and conducting organic polymer, a new class of organic–inorganic composite cation exchanger PANI–Ti(IV) phosphosulphosalicylate (PTPSS) was synthesized by intercalating polyaniline (PANI) into Ti(IV) phosphosulphosalicylate (Ti(IV) PSS) using sol–gel chemical route with enhanced properties. PTPSS has been characterized by using Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDAX), thermo gravimetric analysis (TGA-DTG), and Transmission Electron Microscopy (TEM). Ac electrical conductivity studies were also performed. This material possessed electrical conductivity of 10−3 – 10−6Scm−1which falls in the semiconducting range. The frequency (2 × 105 – 1 × 106 Hz) dependent Ac conductivity at room temperature suggests the evidence for the transport mechanism for the conductivity in PTPSS. The structure of the composite cation exchanger extremely supports its conducting behavior.

    Jan. 01, 1900
  • Vol. 11 Issue 1 2150008 (2021)
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