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Ultrafine Vacancy-Rich Nb_(2)O_(5)Semiconductors Confined in Carbon Nanosheets Boost Dielectric Polarization for High-Attenuation Microwave Absorption 被引量:1
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作者 Zhe Su Shan Yi +5 位作者 Wanyu Zhang Xiaxi Xu Yayun Zhang Shenghu Zhou Bo Niu Donghui Long 《Nano-Micro Letters》 SCIE EI CAS CSCD 2023年第10期478-493,共16页
The integration of nano-semiconductors into electromagnetic wave absorption materials is a highly desirable strategy for intensifying dielectric polarization loss;achieving high-attenuation microwave absorption and re... The integration of nano-semiconductors into electromagnetic wave absorption materials is a highly desirable strategy for intensifying dielectric polarization loss;achieving high-attenuation microwave absorption and realizing in-depth comprehension of dielectric loss mechanisms remain challenges.Herein,ultrafine oxygen vacancy-rich Nb_(2)O_(5)semiconductors are confined in carbon nanosheets(ov-Nb_(2)O_(5)/CNS)to boost dielectric polarization and achieve high attenuation.The polarization relaxation,electromagnetic response,and impedance matching of the ov-Nb_(2)O_(5)/CNS are significantly facilitated by the Nb_(2)O_(5)semiconductors with rich oxygen vacancies,which consequently realizes an extremely high attenuation performance of-80.8 dB(>99.999999%wave absorption)at 2.76 mm.As a dielectric polarization center,abundant Nb_(2)O_(5)–carbon heterointerfaces can intensify interfacial polarization loss to strengthen dielectric polarization,and the presence of oxygen vacancies endows Nb_(2)O_(5)semiconductors with abundant charge separation sites to reinforce electric dipole polarization.Moreover,the three-dimensional reconstruction of the absorber using microcomputer tomography technology provides insight into the intensification of the unique lamellar morphology regarding multiple reflection and scattering dissipation characteristics.Additionally,ov-Nb_(2)O_(5)/CNS demonstrates excellent application potential by curing into a microwave-absorbing,machinable,and heat-dissipating plate.This work provides insight into the dielectric polarization loss mechanisms of nano-semiconductor/carbon composites and inspires the design of high-performance microwave absorption materials. 展开更多
关键词 Electromagnetic wave absorption Nb_(2)O_(5)semiconductor dielectric polarization loss Oxygen vacancy Nb_(2)O_(5)-carbon hetero-interface
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A Review of Wideband Circularly Polarized Dielectric Resonator Antennas 被引量:1
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作者 Ubaid Ullah Mohd Fadzil Ain Zainal Arifin Ahmad 《China Communications》 SCIE CSCD 2017年第6期65-79,共15页
This article presents a technical review of circularly polarized(CP) dielectric resonator antennas(DRA) for wideband applications.The primary objective of this review is,to highlight the techniques used by different r... This article presents a technical review of circularly polarized(CP) dielectric resonator antennas(DRA) for wideband applications.The primary objective of this review is,to highlight the techniques used by different researchers for generating circular polarization in DRA.First,a general idea of circular polarization and it advantages over linear polarization is presented,and then all the major developments made in the CP DRA are highlighted.The emphasis of the paper is on the wideband circularly polarized dielectric resonator antenna.The current state of the art and all the realizable features of the CP DRA are addressed comprehensively.Finally,some recommendations for future CP DRAs are given and the paper ends with concluding remarks. 展开更多
关键词 circularly polarized dielectric resonator antenna dielectric resonator antenna circular polarization techniques
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Tight Focusing Properties of Azimuthally Polarized Pair of Vortex Beams through a Dielectric Interface 被引量:1
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作者 C. A. P. Janet M. Lavanya +3 位作者 K. B. Rajesh M. Udhayakumar Z. Jaroszewicz D. Velauthapillai 《Chinese Physics Letters》 SCIE CAS CSCD 2017年第7期109-113,共5页
Tight focusing properties of an azimuthally polarized Gaussian beam with a pair of vortices through a dielectric interface is theoretically investigated by vector diffraction theory. For the incident beam with a pair ... Tight focusing properties of an azimuthally polarized Gaussian beam with a pair of vortices through a dielectric interface is theoretically investigated by vector diffraction theory. For the incident beam with a pair of vortices of opposite topological charges, the vortices move toward each other, annihilate and revive in the vicinity of focal plane, which results in the generation of many novel focal patterns. The usable focal structures generated through the tight focusing of the double-vortex beams may find applications in micro-particle trapping, manipulation, and material processing, etc. 展开更多
关键词 Tight Focusing Properties of Azimuthally polarized Pair of Vortex Beams through a dielectric Interface
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DIPOLE POLARIZATION RELAXATION AND MOLECULAR STRUCTURE OF MAIN-AND SIDE-CHAIN LIQUID-CRYSTALLINE POLYMERS
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作者 T.P.Stepanova L.L.Burshtein 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 1996年第1期1-18,共18页
Molecular mobility in thermotropic polyesters and side-chain polymers with different struc-ture of mesogens and spacers has been studied by dielectrical method in dilutesolutions. The results made it possible to estab... Molecular mobility in thermotropic polyesters and side-chain polymers with different struc-ture of mesogens and spacers has been studied by dielectrical method in dilutesolutions. The results made it possible to establish the multiplicity of dielectric relaxationtransitions which reflects the small- and large-scale types of molecular motion. It was shownthat dielectric relaxation processes occurring in accordance with local mechanism (relaxationtimes 10^(-9)--10^(-7)s. and the activation energy 10--50kJ/mol) are due to the mobility of kineticchain elements of different length within a monomer units. It was found that the dielectricrelaxation process connected with a large-scale form of molecular motion (relaxation times10^(-5)--10^(-6)s. and the activation energy 100kJ/mol) did not depend on the molecular massbut was infiuenced by factors changing the conformational state of the macromolecule. It isestablished tha the cooperative reorientation mobility of associated mesogenic fragments isthe source of the large-scale process. 展开更多
关键词 Liquid crystal polymers dielectric polarization Relaxation transitions Dilute solution AGGREGATION
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Electrical and dielectric characterization of Au/ZnO/n-Si device depending frequency and voltage
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作者 I Orak A Kocyigit S Ahndal 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第2期477-483,共7页
Au/Zn O/n-type Si device is obtained using atomic layer deposition(ALD) for Zn O layer, and some main electrical parameters are investigated, such as surface/interface state(Nss), barrier height(Φb), series res... Au/Zn O/n-type Si device is obtained using atomic layer deposition(ALD) for Zn O layer, and some main electrical parameters are investigated, such as surface/interface state(Nss), barrier height(Φb), series resistance(Rs), donor concentration(Nd), and dielectric characterization depending on frequency or voltage. These parameters are acquired by use of impedance spectroscopy measurements at frequencies ranging from 10 k Hz to 1 MHz and the direct current(DC) bias voltages in a range from-2 V to +2 V at room temperature are used. The main electrical parameters and dielectric parameters,such as dielectric constant(ε"), dielectric loss(ε"), loss tangent(tan δ), the real and imaginary parts of electric modulus(M and M), and alternating current(AC) electrical conductivity(σ) are affected by changing voltage and frequency. The characterizations show that some main electrical parameters usually decrease with increasing frequency because charge carriers at surface states have not enough time to fallow an external AC signal at high frequencies, and all dielectric parameters strongly depend on the voltage and frequency especially in the depletion and accumulation regions. Consequently, it can be concluded that interfacial polarization and interface charges can easily follow AC signal at low frequencies. 展开更多
关键词 Au/ZnO/n–Si device dielectric properties polarization process frequency and voltage dependence
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Theoretical Study of Antiferrodistortive Phase Transition in Strontium Titanate
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作者 蔡玉平 韩代朝 宁如云 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2010年第2期237-240,I0002,共5页
At 105 K, strontium titanate is known to undergo an antiferrodistortive transition transform-ing from cubic to tetragonal structure as a result of the rotation of the oxygen octahedral around a cubic axe. Based on the... At 105 K, strontium titanate is known to undergo an antiferrodistortive transition transform-ing from cubic to tetragonal structure as a result of the rotation of the oxygen octahedral around a cubic axe. Based on the Curie principle, the order parameter is determined to be a third-order complete symmetry polarization tensor. To take into account of quantum effects,the dielectric permittivity is measured from Landau free energy, and the Curie Weiss-type behavior is analyzed. From crystallization chemistry viewpoint, the dielectric behavior at low temperature is connected to small radius of Sr^2+, which is much easier to move around the oxygen octahedral than Ba^2+ in BaTiO3 or Pb^2+ in PbTiO3. 展开更多
关键词 Spontaneous polarization dielectric permittivity Free energy Antiferrodis-tortive phase transition
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Size-Dependent Oxidation-Induced Phase Engineering for MOFs Derivatives Via Spatial Confinement Strategy Toward Enhanced Microwave Absorption 被引量:10
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作者 Hanxiao Xu Guozheng Zhang +5 位作者 Yi Wang Mingqiang Ning Bo Ouyang Yang Zhao Ying Huang Panbo Liu 《Nano-Micro Letters》 SCIE EI CAS CSCD 2022年第6期294-307,共14页
Precisely reducing the size of metal-organic frameworks(MOFs)derivatives is an effective strategy to manipulate their phase engineering owing to size-dependent oxidation;however,the underlying relationship between the... Precisely reducing the size of metal-organic frameworks(MOFs)derivatives is an effective strategy to manipulate their phase engineering owing to size-dependent oxidation;however,the underlying relationship between the size of derivatives and phase engineering has not been clarified so far.Herein,a spatial confined growth strategy is proposed to encapsulate small-size MOFs derivatives into hollow carbon nanocages.It realizes that the hollow cavity shows a significant spatial confinement effect on the size of confined MOFs crystals and subsequently affects the dielectric polarization due to the phase hybridization with tunable coherent interfaces and heterojunctions owing to size-dependent oxidation motion,yielding to satisfied microwave attenuation with an optimal reflection loss of-50.6 d B and effective bandwidth of 6.6 GHz.Meanwhile,the effect of phase hybridization on dielectric polarization is deeply visualized,and the simulated calculation and electron holograms demonstrate that dielectric polarization is shown to be dominant dissipation mechanism in determining microwave absorption.This spatial confined growth strategy provides a versatile methodology for manipulating the size of MOFs derivatives and the understanding of size-dependent oxidation-induced phase hybridization offers a precise inspiration in optimizing dielectric polarization and microwave attenuation in theory. 展开更多
关键词 Size-dependent oxidation Phase engineering Coherent interface dielectric polarization Electron holography
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Extra-wide bandwidth via complementary exchange resonance and dielectric polarization of sandwiched FeNi@SnO_(2)nanosheets for electromagnetic wave absorption 被引量:4
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作者 Huipeng Lv Chen Wu +2 位作者 Faxiang Qin Huaxin Peng Mi Yan 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2021年第31期1-8,共8页
Advanced electromagnetic(EM)wave absorbers with wide bandwidth is crucial to avoid EM interference and radiation,while achieving compensatio nal attenuation at different frequencies is challe nging.Herein,two-dimensio... Advanced electromagnetic(EM)wave absorbers with wide bandwidth is crucial to avoid EM interference and radiation,while achieving compensatio nal attenuation at different frequencies is challe nging.Herein,two-dimensional(2 D)sandwiched FeNi@SnO_(2)have been designed,for which SnO_(2)nanosheets provide numerous heterogeneous nucleation sites for the growth of dispersive FeNi nanoparticles with reduced size.The SnO_(2)exhibits dipole polarization at 21.45 GHz with a width of~4.00 GHz,while the FeNi nanoparticles induce excha nge resonance at 18.13 GHz(~6.00 GHz width)and interfacial polarization at15.97 GHz(~6.00 GHz width).Such complementary attenuation mechanisms give rise to an impressive ultra-wide effective absorption bandwidth of 11.70 GHz with strong absorption of-49.1 dB at a small thickness of 1.75 mm.Not only superior EM wave absorption is achieved in this work,it also provides a versatile strategy to integrate different loss mechanisms in the design of EM wave absorbers with extra-wide bandwidth. 展开更多
关键词 Sandwiched FeNi@SnO_(2)nanosheets dielectric polarization Exchange resonance Complementary attenuation Electromagnetic wave absorption
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Field-induced phase transitions in chiral smectic liquid crystals studied by the constant current method
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作者 H Dhaouadi R Zgueb +2 位作者 O Riahi F Trabelsi T Othman 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第5期373-379,共7页
In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the(E, T) phase diagram of the studied pr... In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the(E, T) phase diagram of the studied product can be obtained.In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound. 展开更多
关键词 chiral smectic liquid crystal constant current method ferroelectric polarization dielectric permittivity
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Optimizing magnetic/dielectric matching in permalloy/carbonized cotton fiber composites by strain-tunable ferromagnetic resonance and defect-induced dielectric polarization
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作者 Xiaochen Shen Chenglong Hu +4 位作者 Wenling Ren Rongzhi Zhao Lianze Ji Xuefeng Zhang Xinglong Dong 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2022年第29期174-181,共8页
Electromagnetic losses in composites could be synergistically controlled by permeability and permittivity,associated with multiple ferromagnetic resonances and dielectric polarization.However,it is still challenging f... Electromagnetic losses in composites could be synergistically controlled by permeability and permittivity,associated with multiple ferromagnetic resonances and dielectric polarization.However,it is still challenging for simultaneous tunability for both the terms in a magnetic/dielectric composite system.Here,we demonstrate the tunable ferromagnetic resonances and the enhanced dielectric losses at gigahertz frequencies in permalloy/carbonized cotton fiber composites with different annealing temperatures.It is theoretically confirmed that the stress field acting on the magnetic permalloy layer increases with increasing temperature because of the shrinkage of the dielectric carbonized cotton fibers,resulting in multiple ferromagnetic resonances,in which there is a linear relationship(f=1.52×σ+9.38)between the resonance frequency(f)and the stress(σ).The present work provides a fundamental insight into understanding the micromagnetic dynamics of the magnetic/dielectric composite system. 展开更多
关键词 Ferromagnetic resonance Stress tuning dielectric polarization
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Phenomenological Theory of Pyroelectricity
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作者 Manfred Fähnle 《材料科学与工程(中英文B版)》 2020年第2期49-52,共4页
In pyroelectric materials there is a spontaneous dielectric polarization.When raising the temperature,then a voltage appears in the system.In the present manuscript a phenomenological theory of pyroelectricity is deve... In pyroelectric materials there is a spontaneous dielectric polarization.When raising the temperature,then a voltage appears in the system.In the present manuscript a phenomenological theory of pyroelectricity is developed. 展开更多
关键词 PYROELECTRICITY dielectric polarization phenomenological theory MAGNETISM MAGNETOSTRICTION thermal expansion pyromagnetism
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Effect of anionic ordering on the electronic and optical properties of BaTaO2N:TB-mBJ density functional calculation
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作者 K Bettine O Sahnoun +1 位作者 M Sahnoun M Driz 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第5期319-325,共7页
This report presents a first-principles investigation of the structural, electronic, and optical properties of perovskite oxynitrides BaTaO2 N by means of density functional theory(DFT) calculations using the full-p... This report presents a first-principles investigation of the structural, electronic, and optical properties of perovskite oxynitrides BaTaO2 N by means of density functional theory(DFT) calculations using the full-potential linearized augmented plane wave(FP-LAPW) method. Three possible structures(P4mm, I4/mmm, and Pmma) are considered according to the TaO4N2 octahedral configurations. The calculated structural parameters are found to be in good agreement with the previous theoretical and experimental results. Moreover, the electronic band structure dispersion, total, and partial densities of electron states are investigated to explain the origin of bandgaps and the contribution of each orbital's species in the valence and the conduction bands. The calculated minimum bandgaps of the P4 mm, I4/mmm, and Pmma structures are 1.83 e V, 1.59 e V, and 1.49 e V, respectively. Furthermore, the optical properties represented by the dielectric functions calculated for BaTaO2 N show that the I4/mmm phase absorbs the light at a large window in both the visible and UV regions,whereas the other two structures(P4mm and Pmma) are more active in the UV region. Our investigations provide important information for the potential application of this material. 展开更多
关键词 anionic perovskite octahedral bands dielectric augmented polar ordering struc orbital
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Refractive index measurement of dielectric samples using highly focused radially polarized light(Invited Paper)
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作者 Guadalupe López-Morales Victor-Manuel Rico-Botero +1 位作者 Rafael Espinosa-Luna Qiwen Zhan 《Chinese Optics Letters》 SCIE EI CAS CSCD 2017年第3期12-15,共4页
In this Letter, a refractive index measurement of a dielectric sample using highly focused radially polarized light is reported. Through imaging analysis of the optical field at the pupil plane of a high numerical ape... In this Letter, a refractive index measurement of a dielectric sample using highly focused radially polarized light is reported. Through imaging analysis of the optical field at the pupil plane of a high numerical aperture (NA) objective lens reflected by the sample under study, the Brewster angle is found. Employing a high NA objective lens allows the measurement of multiple angles of incidence from 0° to 64° in a single shot. The refractive index of the sample is estimated using the measured Brewster angle. The experimental results are compared with the theoretical images computed with the Fresnel theory, and a good agreement is obtained. 展开更多
关键词 high Refractive index measurement of dielectric samples using highly focused radially polarized light
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Large effective piezoelectric response from the spontaneously polarized surface layer in P(VDF-TrFE)arch films
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作者 Xinping Hu Yuhong Zhu Baojin Chu 《Journal of Advanced Dielectrics》 2022年第6期40-47,共8页
In this work,we show that a d_(33)~150 pC/N can be obtained in nonpoled poly(vinylidene fluoride trifluoroethylene)(P(VDF-TrFE))copolymer films with an arch structure.The copolymer films,which are often thought to be ... In this work,we show that a d_(33)~150 pC/N can be obtained in nonpoled poly(vinylidene fluoride trifluoroethylene)(P(VDF-TrFE))copolymer films with an arch structure.The copolymer films,which are often thought to be homogeneous,are in fact inhomogeneous in microstructure and physical properties after film fabrication.Although a large proportion of the copolymer film is nonpolar,as expected in a nonpoled ferroelectric film,the surface regions of the film are spontaneously polarized.We propose that inhomogeneous stress in the surface regions,which is either from the constraint of the substrate or skin layer effect formed during the film fabrication,generates a flexoelectric response and orients the spontaneous polarization of the ferroelectric film.As a result of the polar surface regions,the nonpoled films exhibit a piezoelectric response.The piezoelectric response is further amplified by the special arch structure of the films,leading to the observed large effective piezoelectric response.This study not only discovers the polar surface effect in ferroelectric polymer films,but also proposes an approach to design polymer materials with a strong piezoelectric response. 展开更多
关键词 Ferroelectric films dielectric polarization PIEZOELECTRICITY SURFACES
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Evidence of a third kind of Johnscher’s like universal dielectric response
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作者 Maheswar Panda 《Journal of Advanced Dielectrics》 CAS 2018年第4期43-48,共6页
Polymer/metal composites(PMC)comprising of polyvinylidene fluoride/nanocrystalline nickel with varying volume fractions of nickel(fcon)prepared under cold press show an insulator to metal transition(IMT)at percolation... Polymer/metal composites(PMC)comprising of polyvinylidene fluoride/nanocrystalline nickel with varying volume fractions of nickel(fcon)prepared under cold press show an insulator to metal transition(IMT)at percolation threshold(f_(c)=f_(con)=0:27).The two kinds of generalized Johnscher’s universal dielectric response(UDR)laws on both sides of IMT hold good,while for the percolative sample,none of the two laws hold good.Neither the concept of dipolar relaxation nor anomalous low frequency dispersion stands valid for f_(c)=0:27,while a completely different,neutral and competing electrical behavior is observed over the entire range of frequencies.The emerged third kind of Johnscher’s like UDR for fc is observed and the relaxation law has been formulated as the ratio of imaginary and real parts of dielectric constant remains constant over the entire range of frequency starting from dc to any higher frequency.The value of the constant is attributed to depend on the PMC,the dielectric constant of the polymer,the differences of conductivity and fractions of the components of the PMC and also on their connectivity arising due to the difference of their process conditions.The emerged unique dielectric relaxation consists of multiple relaxations arising due to the combination of other relaxations(arising due to the two different types of species)present in the sample,f_(con)=0:27.This novel material may be suitable for certain specific applications in electrical and electronics engineering. 展开更多
关键词 dielectric losses dielectric materials dielectric measurements dielectric polarization frequency response image analysis impedance measurement POLYMERS relaxation processes SPECTROSCOPY
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Isotope effect on the Casimir force
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作者 Lanyi Xie Fuwei Yang Bai Song 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS CSCD 2023年第10期131-137,共7页
Isotopic dependence of the Casimir force is key to probing new physics and pushing novel technologies at the micro and nanoscale, but is largely unexplored. In 2002, an isotope effect of 10^(-4) was estimated for met... Isotopic dependence of the Casimir force is key to probing new physics and pushing novel technologies at the micro and nanoscale, but is largely unexplored. In 2002, an isotope effect of 10^(-4) was estimated for metals—orders of magnitude beyond the experimental resolution. Here, by employing the Lifshitz theory, we reveal a significant isotope effect of over 10^(-1) for polar dielectrics. This effect arises from the isotope-mass-induced line shift of the zone-center optical phonons and is insensitive to the linewidth. We perform numerical analyses on both the imaginary and real-frequency axes, and derive analytical formulas for predicting the isotope effect. The three-orders-of-magnitude difference between polar dielectrics and metals arises from the distinct isotopic dependence of the phonon and plasma frequencies. Our work opens up a new avenue for engineering forces at small scales and may also facilitate the quest for the fifth force of nature. 展开更多
关键词 isotope effect Casimir force polar dielectric phonon line shift plasma frequency
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Investigation on refractive index sensing of single silver nanoparticle at tightly focused light illumination 被引量:1
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作者 SHEN Si WANG Xiang-hui +2 位作者 SUN Jing-wei FAN Fei CHANG Sheng- jiang 《Optoelectronics Letters》 EI 2017年第1期5-9,共5页
Based on the generalized Mie theory,refractive index sensing characteristics of single silver nanoparticle respectively illuminated by tightly focused linearly-polarized and radially-polarized light beams are investig... Based on the generalized Mie theory,refractive index sensing characteristics of single silver nanoparticle respectively illuminated by tightly focused linearly-polarized and radially-polarized light beams are investigated. The spectra for localized surface plasmon resonances(LSPR) under different dielectric environments demonstrate that distinct dipolar and quadrupolar resonances can be always observed for the case of radial polarization,while there is only strong dipolar resonance for the case of linear polarization. The dipolar mode has a higher sensitivity. However,the figure of merit(FOM) for the quadrupolar resonance is much higher than that for the dipolar resonance,because the quadrupolar resonance has a narrower width. 展开更多
关键词 tightly illumination silver refractive dielectric polarized linearly plasmon figure scattered
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Surface potential uniformity and sensitivity of large-area PTFE electret discs of different thicknesses produced by a modified corona poling rotating system for dosimetry applications
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作者 A.Komeijani H.Bagheri B.Shekarchi 《Journal of Advanced Dielectrics》 CAS 2019年第6期52-62,共11页
In this study,large-area(6-cm diameter)Teflon polytetrafluoroethylene(PTFE)discs of different thicknesses(0.2-,0.5-and 1-mm)were negatively and positively charged by using the“modified single point-to-plane corona po... In this study,large-area(6-cm diameter)Teflon polytetrafluoroethylene(PTFE)discs of different thicknesses(0.2-,0.5-and 1-mm)were negatively and positively charged by using the“modified single point-to-plane corona poling rotating system”.The effects of some crucial parameters of the PTFE disc as well as the modified corona poling rotating system on the PTFE surface potential uniformity such as.(a)PTFE disc thickness,(b)PTFE disc polarity and(c)needle-to-PTFE disc distance were successfully reported.Accordingly,closer needle-to-PTFE disc distance,positive charging mode and thinner PTFE disc provided a better PTFE surface potential uniformity.However,the effects of PTFE charge polarity and needle distance on the electrostatic charge potential uniformity were much more remarkable in comparison with the effects of PTFE thickness.Additionally,the surface potential distribution profiles of charged PTFE discs were totally flat and independent of the PTFE thickness at 5-and 13-mm needle distances for the negative and positive charging modes,respectively.At the optimized charging conditions,large-area PTFE electret disc(0.5-mm-thick)with positive uniform surface charge potential especially at the edges up to1.8 kV with stability up to 77 days studied was produced by applying a new multiple heat treatment protocol to the PTFE disc for radon dosimetry.As also observed in this study,the sensitivity of PTFE electret dosimeters to a defined radon gas concentration increases as the PTFE thickness increases.Meanwhile,0.5-mm-thick PTFE electret disc produced was selected to be used as a high quality electret dosimeter with acceptable and superior parameters for different applications in particular medium-term radiation dosimetry in both low and high dose rate ionizing radiation fields. 展开更多
关键词 PTFE electrets dielectric polarization surface charge uniformity and stability electrostatic discharges and measurements DOSIMETRY
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