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이규탁,고중혁 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.2
In this paper, we will introduce the microwave properties of Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors fabricated on alumina substrates. The tailored paraelectric state of Ag(Ta,Nb)O3 allows the material to be regarded as a part of the family of microwave materials. As thick films formed in our experiment, Ag(Ta,Nb)O3 exhibited extremely low dielectric loss with relatively high dielectric permittivity. This low dielectric loss is a very important issue for microwave applications. Therefore, we investigated the microwave properties of Ag(Ta0.8Nb0.2)O3thick film planar type interdigital capacitors. Ag(Ta0.8Nb0.2)O3 thick films were prepared by a screen-printing method on alumina substrates and were sintered at 1140 C for 2 hrs. The XRD analysis results showed that the Ag(Ta0.8Nb0.2)O3 thick film has the perovskite structure. The frequency dependent dielectric permittivity showed that these Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors have very weak frequency dispersions with low loss tangents in the microwave range. In this paper, we will introduce the microwave properties of Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors fabricated on alumina substrates. The tailored paraelectric state of Ag(Ta,Nb)O3 allows the material to be regarded as a part of the family of microwave materials. As thick films formed in our experiment, Ag(Ta,Nb)O3 exhibited extremely low dielectric loss with relatively high dielectric permittivity. This low dielectric loss is a very important issue for microwave applications. Therefore, we investigated the microwave properties of Ag(Ta0.8Nb0.2)O3thick film planar type interdigital capacitors. Ag(Ta0.8Nb0.2)O3 thick films were prepared by a screen-printing method on alumina substrates and were sintered at 1140 C for 2 hrs. The XRD analysis results showed that the Ag(Ta0.8Nb0.2)O3 thick film has the perovskite structure. The frequency dependent dielectric permittivity showed that these Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors have very weak frequency dispersions with low loss tangents in the microwave range.
문상호,고중혁,김세호 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.41
The dielectric and the electrical properties of ZnBO-doped (Ba,Sr)TiO3 thick films on alumina substrates were investigated. 1-, 3-, and 5-wt% ZnBO doped BST thick films were prepared by using the screen printing method on the alumina substrates, which were sintered at 1200 ℃. The frequency-and temperature-dependent dielectric properties were investigated. Current-voltage characteristics were investigated in the temperature range from 303 to 373 K with different doping contents (1-, 3-, and 5-wt% ZnBO-doped BST). The temperature-dependent resistivity was calculated. The leakage current density of the 5-wt% ZnBO-doped BST thick film was only 35 pA /cm2at an applied electric field of 4 kV/cm, while those at the 1- and 3-wt% ZnBO-doped BST thick films were 59 and 44 pA/cm2, respectively. From the temperature-dependent current - voltage characteristics, we confirmed that ZnBO-doped BST thick films show and negative temperature coefficients of resistivity (NTCR).
Li Dopant가 ZnO 세라믹스의 전기적 특성과 미세 구조에 미치는 영향
전민철,고중혁,Jun, Min-Chul,Koh, Jung-Hyuk 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.4
It is well known that Zinc Oxide (ZnO) is an attractive material for its various applications. ZnO has been mostly used as a transparent conducting oxide in liquid crystal displays, solar cells due to its advantages of low cost, high productivity, and excellent electrical conductivity. Notably, flexible-dye-sensitized solar cells (DSSCs) based on polyethylene terephthalate (PET) substrates require low temperature sintering processing conditions. Therefore, low temperature processing conditions have been strongly required for transparent conducting film applications. In this paper, we prepared low temperature-sintered ZnO ceramics employing Li as a sintering aid.
함용수,고중혁 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.41
Three (3)-wt% Li2CO3 doped (Ba0.5,Sr0.5)TiO3 thick films were prepared and sintered at a relatively low temperature (900 ℃) for electronic device applications. The thick films were prepared via a screen printing process on Ag-Pd printed alumina substrates. In this experiment, the crystalline and the electrical properties of Li2CO3-doped (Ba0.5,Sr0.5)TiO3 thick films on the Ag-Pd printed alumina substrates sintered at 900 ℃ were investigated. To investigate the electrical properties,we employed impedance spectroscopy and ac conductivity. In this study, we found that the 3-wt%Li2CO3 doped (Ba0.5,Sr0.5)TiO3 thick film exhibited perovskite and pseudo-cubic structures. Also,the relative dielectric permittivity of the 3 wt% Li2CO3 doped (Ba0.5,Sr0.5)TiO3 thick film was 149.25 at 30 ℃, and the activation energies were 0.432 and 0.326 eV at 1 and 81.57 kHz, respectively. The resistances of the grain and the grain boundary were 17.65 kΩand 40.5 kΩat 130 ℃,respectively.
Effects of Ag2O Dopants on the Piezoelectric Properties of 0.94(K0.5Na0.5)NbO3-0.06LiNbO3 Ceramics
채문순,고중혁 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.2
Lead-free piezoelectric Ag2O-doped 0.94(K0.5Na0.5)NbO3-0.06LiNbO3 ceramics were investigated for their piezoelectric properties through use of a conventional sintering process. The effects of Ag dopants on the microstructure and the electrical properties of 0.94(K0.5Na0.5)NbO3-0.06LiNbO3 ceramics were systematically investigated. Ag dopants were added to 0.94(K0.5Na0.5)NbO3-0.06Li NbO3 ceramics at 1, 2, 3, 4, 5, 6, 7, and 8 mol%. X-ray diffraction analysis was performed to determine the structural properties and the lattice parameters. Piezoelectric constants and the temperature-dependent dielectric permittivity were measured. When the 7 mol% Ag2O-doped 0.94(K0.5Na0.5)NbO3-0.06LiNbO3 specimens were sintered at 1080 °C for 5 h, it showed the highest values of the density (4.32 g/cm3), the piezoelectric constant(d33) (274 pC/N) and the phase transition temperature Tc (465 °C).