强誘電體의 分極에 미치는 溫度의 影響

이충호 忠州大學校 2008 한국교통대학교 논문집 Vol.43 No.-

The electric properties of PbMg1/3Nb2/3O3(PMN), PbFe1/2Nb1/2O3(PFN) and PbLi1/4Nb3/4O3(PLN) of ferroelectric relaxor composition was studied which was capable of sintering in lower temperature and having superior characteristics to BT system. 0.7PMN-0.25PFN-0.05PLN was mixed and calcined and then the dielectric properties of samples were tested followed by sintering at 1000~1100[℃] during 1~3hrs. From D-E hysteresis curves, the role of dielectric polarizability and the resultant sequence of polar variants was discussed that it is most important profound influence on dielectric properties. The results are as follows; 1. As the sintering temperature was increased, dielectric permittivity was also increased, but dielectric loss factor was decreased. The dielectric permittivity and loss factor was saturated at above 1050[℃]. In the dielectric permittivity versus sintering temperature experiment, somewhat different result was induced. The saturation was occurred at above 1050[℃], dielectric permittivity was decreased, as sintering time was increased. 2. It is shown that the surrounded area of hysteresis loop is increased, as dielectric loss factor is also increased. The area means the energy flowed into the unit area of ferroelectrics and it was consumed by heat in ferroelectrics and became the dielectric loss. 3. The fact that the dielectric permittivity increased, as remained polarization increased and coercive electric field decreased was shown in experiments but not in sintered at 1050[℃] during 3hrs. The relationships between the dielectric permittivity and remained polarization and coercive field should be studied more seriously.

삽입손실 개선을 위한 링 접촉식 구조의 L대역 로터리조인트 설계

나재현(Jae-Hyun Na),노돈석(Don-Suk Roh),김동길(Dong-Gil Kim) 한국전자통신학회 2019 한국전자통신학회 논문지 Vol.14 No.1

본 논문에서는 추적 레이더시스템의 핵심부품인 L대역 로터리조인트의 설계를 다룬다. 로터리조인트는 추적시스템 안테나 회전부에 장착되어 회전하는 안테나와 고정된 신호처리부를 연결하는 구성품으로 안테나의 회전시에도 꼬임이 없이 RF신호를 원활하게 전달하는 주요부품이다. 로터리조인트의 신호 삽입손실을 개선하기 위해, 유전체 종류, 급전분배링 형상 및 유전체 형상 등을 다양하게 수정하였다. 제안한 로터로조인트는 해외 도입품과 비교하여 향상된 성능을 확인하였다. 도입품 로터리조인트의 최대 삽입손실은 1.26dB이었으나, 본 논문에서 제안한 로터리조인트의 최대 삽입손실은 0.68dB로 도입품 대비 약 46%정도 개선되는 것을 확인하였다. This paper deals with the design of the L-band rotary joint, which is a core part of the tracking radar system. The rotary joint is a part that is mounted on the rotating parts of the tracking system antenna, which smoothly transmits RF signals with minimizing signal insertion loss. To improve the insertion loss of rotary joint, 1) dielectric materials, 2) design of distribution ring and 3)dielectric shape are studied. The performance of proposed rotary joint is compared with the conventional product. The prototype rotary joint showed a max insertion loss of 0.68dB, that is improved about 46% compare with conventional product which insertion loss was 1.26dB.

루타일이 삽입된 유전체 공진기의 두 공진 모드를 이용한 루타일의 유전손실과 $YBa_2Cu_3O_{7-{\delta}}$ 박막의 마이크로파 표면저항 측정

임준,이재훈,김민정,허정,이상영,Lim, J.,Lee, J.H.,Kim, M.J.,Hur, J.,Lee, S.Y. 한국초전도학회 2003 Progress in superconductivity Vol.4 No.2

In measuring the microwave surface resistance of high-Tc superconductor (HTS) films using the dielectric-loaded cavity resonator method, one of the most important factors that limit the measurement sensitivity is the measurement error in the loss tangent ($tan\delta$) of the dielectric rod placed inside the cavity. We have measured the effective surface resistance ( $R_{S}$ $^{eff}$) of$ YBa_2$$_Cu3$$_{7-{\delta}}$ (YBCO) films and the $tan\delta$ of rutile ($TiO_2$) using the 'two-tone'method suggested by Kobayashi et at. [IEEE, MTT-S Digest, 495, (2001)], which enables simultaneous measurements of both the $R_{S}$ $^{eff}$ fof HTS films and the $tan\delta$ of the rutile with high sensitivity. A rutile-loaded cavity resonator with the $TE_{012}$ and $TE_{021}$ resonant frequencies at 13.67 - 14.01 GHz is used for this purpose. At temperatures where the two modes do not couple with other modes, the $R_{S}$ $^{eff}$ of YBCO films and $tan\delta$ of rutile measured by the two-tone method appear to match well with the corresponding values measured using the reported $tan\delta$ values of sapphire within 10 %. Usefulness of the 'two-tone' method for microwave characterization of HTS films and dielectrics is discussed.d.ielectrics is discussed.ussed.

Realizing Rationally-Balanced Dielectric Properties in Fluoropolymer/Cr2AlC MAX Composites Modified by 2D-BN

Qin Li,Junquan Zhou,Yanhui Chen,Xiaofeng Xia,Maolin Bo,Qihuang Deng,Yefeng Feng 한국고분자학회 2020 Macromolecular Research Vol.28 No.13

Polymer/conductor composite dielectric materials have a high dielectric constant. In recent years, composite dielectrics have become a study hotspot in highdensity energy storage capacitors. However, high dielectric loss and high electrical conductivity make the application of the composite materials very limited. In order to obtain composite materials with high dielectric constant, low dielectric loss and low conductivity, we added the insulating boron nitride (BN) filler into polymer/Cr2AlC composites. As a conductive filler, Cr2AlC ternary-layered-compound (MAX) ceramic has an interface polarization with the polymer matrix, thereby increasing the dielectric constant of the composites. The insulating BN has a very low electrical conductivity, which can effectively reduce the electrical conductivity and dielectric loss of the composites. Compared with the binary polymer/Cr2AlC composite materials, the ternary polymer/Cr2AlC/BN composite materials can achieve the low dielectric loss and low conductivity as well as properly-lowered dielectric constant. The ternary composite material filled with 10 wt% Cr2AlC and 2 wt% BN has a dielectric constant of about 30, a dielectric loss of about 0.7 and a conductivity of about 4.6×10- 7 S m-1 at 100 Hz. In this work, high-performance composite dielectrics were prepared through good cooperation between conductive and insulating ceramic fillers, which might provide an idea for design of promising energy storage capacitors.

IMPROVEMENT IN TUNABILITY AND DIELECTRIC LOSS OF BSTZ FERROELECTRIC THIN FILMS USING POST-ANNEALING

Ha, Jong-Yoon,Kang, Chong-Yun,Choi, Ji-Won,Sim, Sung-Hun,Karmanenko, S. F.,Yoon, Seok-Jin,Kim, Hyun-Jai Taylor Francis 2006 Integrated ferroelectrics Vol.86 No.1

<P> The change in dielectric constant of ferroelectric materials as a function of electric field is the key to wide range of applications such as tunable oscillators, delay lines, and phase shifters. The effect of the post-annealing on the dielectric properties of (Ba0.6Sr0.4)(Ti0.9Zr0.1)O3 (BSTZ) thin films deposited by Pulsed Laser Deposition is studied. BSTZ ferroelectric thin films showed simple cubic perovskite structure having (200) preferred orientation independent on deposition conditions. Preferred orientation slightly increased after post-annealing. With increasing the oxygen pressure, the dielectric loss of ferroelectric thin films decreased due to the oxygen vacancies. The reason why the dielectric constant increased was due to expansion of unit cell volume leading the increase of ion polarizability. The structure of ferroelectric thin film did not change after post-annealing. The grain size, dielectric constant and tunability were increased; however dielectric loss was decreased after annealing. The microstructure of ferroelectric thin film was one of the important facts(stress between thin films and substrates, thermal conductivity etc) effecting the dielectric properties such as dielectric constant, dielectric loss and tunability etc. Microwave dielectric properties of (Ba0.6Sr0.4)(Ti0.9Zr0.1)O3 ferroelectric thin film were obtained at deposition temperature 750°C, oxygen pressure 200 mTorr, and post-annealing conditions 1100°C for 1h: dielectric constant 2060, dielectric loss 0.0026 and tunability 25.3%.</P>

Finely-reconciled high dielectric constant and low dielectric loss in ternary polymer/Cr2C3/montmorillonite composite films by filler-synergy strategy

Deng Qihuang,Zhou Junquan,Li Xianping,Feng Yefeng,Liang Yurun,Liu Qihang 한국물리학회 2021 Current Applied Physics Vol.22 No.-

Polymer/conductive ceramic composites with high dielectric constant have become research hotspot of dielectric capacitor materials. However, the conductivity and dielectric loss increase when high dielectric constant is achieved. In order to reconcile high dielectric constant and low dielectric loss, in this study, poly (vinylidene fluoride) (PVDF)/chromium carbide (Cr2C3)/montmorillonite (MMT) ternary composite films were prepared by solution cast. Dielectric response based on interfacial polarization was improved and dielectric constant of composites was increased. MMT ceramic was used to suppress interface leakage current. Compared with PVDF/ Cr2C3 composites, the conductivity and dielectric loss of ternary composites were reduced.

Suppression of Dielectric Loss at High Temperature in (Bi_1/2Na_1/2)TiO₃ Ceramic by Controlling A-site Cation Deficiency and Heat Treatment

( Ju-hyeon Lee ),( Geon-ju Lee ),( Thuy-linh Pham ),( Jong-sook Lee ),( Wook Jo ) 한국센서학회 2020 센서학회지 Vol.29 No.1

Dielectric capacitors are integral components in electronic devices that protect the electric circuit by providing modulated steady voltage. Explosive growth of the electric automobile market has resulted in an increasing demand for dielectric capacitors that can operate at temperatures as high as 400 ℃. To surpass the operation temperature limit of currently available commercial capacitors that operate in temperatures up to 125 ℃, Bi_1/2Na_1/2TiO₃ (BNT), which has a large temperature-insensitive dielectric response with a maximum dielectric permittivity temperature of 300 ℃, was selected. By introducing an intentional A-site cation deficiency and post-heat treatment, we successfully manage to control the dielectric properties of BNT to use it for high-temperature applications. The key feature of this new BNT is remarkable reduction in dielectric loss (0.36 to 0.018) at high temperature (300 ℃). Structural, dielectric, and electrical properties of this newly developed BNT were systematically investigated to understand the underlying mechanism.

고주파 기판용 PTFE 복합체 형성 압력에 따른 유전 특성

최홍제,전명표,조용수,조학래,Choi, Hong Je,Chun, Myung Pyo,Cho, Yong Soo,Cho, Hak Rae 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.6

PTFE composites for use of microwave substrate were fabricated by impregnation and heat treatment fabrication with glass fabric. This study shows dielectric properties such as dielectric constant and loss can be controlled by thickness of PTFE composite with change of pressure condition in heating press process. The dielectric constant of the PTFE composites has decreasing tendency as given higher pressure condition. The dielectric loss has similar result too. Especially, the case of the dielectric loss was affected by the condition of pressure at heating press and had the best performance under 3 MPa. In order to see the reason why thickness conditions make different, their microstructures were also observed.

Dielectric Properties of Epoxy/Micro-sized Alumina Composite and of Epoxy/Micro-sized/Nano-sized Alumina Composite

박재준 한국전기전자재료학회 2015 Transactions on Electrical and Electronic Material Vol.16 No.6

Epoxy/micro-sized alumina composite was prepared, and the effects of alumina content on the dielectric properties were investigated in order to develop an insulation material for gas-insulated switchgears (GIS). Nano-sized alumina (average particle size: 30 nm) was also incorporated into the epoxy/micro-sized alumina composite. Dielectric tests were carried out in ASTM D 150, and capacitance (Cp) and dielectric loss (tanδ) were measured. The dielectric constant increased with increasing alumina content in the epoxy/micro-alumina system and the epoxy/microalumina/nano-alumina system. As 1,3-diglycidyl glyceryl ether (DGE) content increased, the dielectric constant decreased and dielectric loss increased. This ocurred as a result of the weak electric field enhancement due to homogeneous dispersion of micro- and nano-sized alumina particles in an epoxy composite.

이종의 유리형성제가 포함된 (50-x)MoO₃-zV₂O??-50P₂O(x-10-40)계 유리의 유전특성에 관한 연구

송인걸,김현철 대전대학교 기초과학연구소 1998 自然科學 Vol.9 No.1

(50-x)MoO₃-xV₂O??-50P₂O??(x=10-40)계 유리의 교류전도도, 유전율 및 유전손실이 온도와 주파수의 함수로 조사되었다. 교류전도도의 조사로부터 전도도는 절단주파수를 중십으로 저주파수에서는 전도도의 값들이 온도에 의존하고 저주파수에서는 주파수에 의존하였으며, MoO₃의 함량이 감소하고 온도가 증가함에 따라 전도도는 증가하는 것으로 나타났다. 유전율은 주파수가 증가함에 따라 감소하였고 온도가 증가하고 MoO₃의 함량이 감소함에 따라 증가하는 것으로 나타났다. 유전손실은 주파수가 증가함에 따라 감소하였으며 온도가 증가함에 따라 주파수의존성이 지수적인 변화에서 선형적인 변화로 나타났다. 또 유전손실은 동일온도에서 MoO₃의 함량이 감소하고 V₂O??의 함량이 증가함에 따라서는 역시 주파수의존성이 지수적 변화에서 선형적인 변화로 나타났으며, 선형변화로의 전이온도는 증가하는 것으로 나타났다. 유전손실의 주파수와 온도의존성에 대한 이와 같은 현상은 직류전도도에서 Debye온도와 밀접한 관계가 있는 것으로 생각되며 이에 대한 연구가 좀 더 진행되어야 할 것으로 생각된다. The temperature dependence of ac-conductivity, dielectric constant and dielectric loss of a (50-x)MoO₃-xV₂O??-50P₂O??(x=10-40) glass system in the range of 25-200℃ have been investigated, as a function of frequency within 200Hz-20kHz. At lower frequency than the threshold frequency, the ac-conductivity depended on the temperature, whereas, at high frequency, it depended on the frequency. And as the temperature raised and MoO₃content decreased, it decreased. As the frequency increased, the dielectric constant decreased and as the temperature raised and MoO₃content decreased, it increased. As the frequency increased, the dielectric loss decreased, And as the temperature raised and MoO₃content decreased at the same temperature, the frequency dependence of dielectric loss was changed from exponential decay to linear and linearized temperature decreased, as MoO₃content decreased. We think that there is a relationship between these phenonmena of dielectric loss and Debye temperature of its dependent dc-conductivity. It is necessary to study more detail about this pheuomeuon.