Effect of the Firing Conditions on the Phase Formation of Alkali Metal Niobate Piezoelectric Ceramics

전명표,강경민,조정호,김병익 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.31

The effects of the sintering atmosphere on the phase formation of lead-free piezoelectric ceramics such as (Bi_(0.5)Na_(0.5))TiO_3 (BNT), (K_(0.5)Na_(0.5)) NbO_3 (KNN), and AZrO_3 modified KNN (A = Ca, Sr, Ba) were investigated with X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Energy dispersive spectrometer (EDS). The ceramic powders mentioned above were synthesized by using a solid state reaction and were pressed into a disk shape. Disk samples of BNT were sintered for 3h in air, N_2 and reduced atmospheres (3%H_2-97%N_2, 10%H_2-90%N_2) at 1000 ℃, respectively. Disk samples of KNN and AZr_O3 modified KNN were sintered for 3h in air at 1160 ℃ and in 3%H_2-97%N_2 atmosphere at 1140 ℃, respectively. In the case of BNT samples sintered in neutral and reduced atmosphere, the vaporization of Bi is serious, while KNN samples show pure perovskite structure and no significant evaporation of K and Na regardless of the sintering atmospheres in contrast with BNT. In the case of AZrO_3 modified KNN (A = Ca, Sr, Ba), with increasing A-site ionic radius, the lattice parameter increases and the monoclinic angle decreases toward 90˚, which seems to induce a phase transition from orthorhombic to tetragonal phase.

세라믹 패키지를 이용한 표면실장형 다이오드의 제작과 특성평가

전명표,조상혁,한익현,조정호,김병익,유인기,Chun, Myoung-Pyo,Cho, Sang-Hyeok,Han, Ik-Hyun,Cho, Jeong-Ho,Kim, Byung-Ik,Yu, In-Ki 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.5

Generally, a diode package consists of the synthetic resin that has good durability but low thermal conductivity. The surface mounted type fast recovery diode was fabricated by using ceramic package. Its main manufacture processes are composed of soldering, sillicon coating and side termination. And it has various advantages that diode is small, easy manufacture and fast cooling. The electric characteristics of the diode such as reverse recovery time, breakdown voltage, forward voltage, and leakage current were 5.28 ns, 1322 V, 1.08 V, $0.45\;{\mu}A$, respectively.

$BaTiO_3$의 입도와 분체특성과의 상관 관계 연구

전명표,조정호,김병익,Chun, M.P.,Cho, J.H.,Kim, B.I. 한국결정성장학회 2005 한국결정성장학회지 Vol.15 No.6

수열합성법에 의해 제조된 티탄산바륨 (BT01, BT02, BT03, BT04, BT05)의 입자크기와 분체특성과의 상관관계를 비표면적, 제타전위, XPS, XRD 및 SEM에 의해 조사하였다. 레이져광산법에 의해 측정된 입자의 크기는 비표면적과 XRD를 통해 결정된 격자이방성과 밀접한 관계가 있음을 보였다. 분말의 비표면적은 입자의 크기가 증가함에 따라 감소하였으며, BT03 시료는 동일한 입자크기의 BT04에 비하여 큰 비표면적을 보였으며, 이는 입자들의 응집에 기인하는 것으로 SEM사진 및 XRD 분석을 통하여 밝혀졌다. 입자의 크기가 증가함에 따라 제타전위는 증가하는 경향을 보였으며, BT02와 BT03 분말은 다른 분말에 비하여 제타전위가 큰 음의 값을 나타내었다. XPS 분석결과 분쇄시 티탄산바륨과 물 사이의 반응에 의한 $Ba^{2+}$ 이온의 용출과 관련이 있는 것으로 분석되었다. The relationship between particle size of hydro-thermally synthesized barium titanate powders (BT01, BT02, BT03, BT04, BT05) and the powder properties was investigated by means of particle size, specific surface area, zeta potential, XPS, XRD and SEM. Particle size determined by laser light scattering is closely related with specific surface area and the tetragonality (c/a) obtained from XRD. The specific surface area of the samples inversely decreased with increasing particle size except BT03 powder. BT03 sample showed higher surface area than BT04 sample of equivalent particle size, which was attributed mostly to the agglomeration of particles in terms of SEM image and XRD analysis. Zeta potential increased with increasing particle size with the exception of BT02 and BT03 which showed larger minus value of zeta potential in comparison with other BT powders. Beta potential results of BT02 and BT03 are considered to be related with the dissolution of $Ba^{2+}$ ion in these powers which was examined by XPS.

한국 IT 산업 발전 방향과 과제

전명표,고정민 에스케이텔레콤 (주) 2001 Telecommunications Review Vol.0 No.-

I T 산업은 21세기에도 매출액과 부가가치 면에서 우리나라의 주력산업이 될 것이다. 그러나 우리나라는 아직도 선진국과의 기술격차로 인한 과다한 기술료 지불 등의 어려움을 겪고 있으며 중국을 위시한 후발국의 추격으로 인한 시장경쟁력 저하의 어려움을 동시에 겪고 있다. 따라서 한국의 I T 산업은 새로운 전략을 필요로 하며 또한 국가적 지원체계의 혁신을 요구하고 있다. 본 논문에서는 21세기 I T산업의 환경변화 추이를 알아보고 우리나라의 IT산업의 경쟁력을 인력, 프로세스, 산업 여건 등 세 가지 범주의 경쟁요소를 기본으로 분석하였다. 그리고 각 경쟁요소 측면에서 도출할 수 있는 경쟁력 강화방안을 제시하였다.

BaTiO₃ PTC 써미스터의 미세구조 및 전기적 특성에 대한 SiO₂ 영향

전명표,Chun, Myoung-Pyo 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.1

PTCR ceramics of $(Ba_{0.998}Sm_{0.002})TiO_3+0.001MnCO_3+xSiO_2$ (x=1, 2, 3, 4, 5, 6 mol%) were fabricated by solid state method. Disk samples of diameter 5 mm and thickness about 1mm were sintered at $1,290^{\circ}C$ for 2 h in reduced atmosphere of $5%H_2-95%N_2$ followed by re-oxidation at $600^{\circ}C$ for 30 min. in $20%O_2-80%N_2$.and their microstructures and electrical properties were investigated with SEM and Multimeter. The color of sintered samples was strongly dependent on $SiO_2$ content showing that the color of samples with $SiO_2$ of 1~2 mol% was gray but that of samples with $SiO_2$ of 4~6 mol% was changed from gray to blue, which seems to be related with the reduction of samples due to the oxygen vacancies created during the sintering in reduced atmosphere. $SiO_2$ content had a great influence on the microstructure and the electrical properties. With increasing $SiO_2$ content, the grain size of samples increased and the resistivity as well as the resistivity jump ($R_{285}/R_{min}$) decreased, which is considered to be attributed to the resistivity change at grain interior and grain boundary due to the fast mass transfer through $SiO_2$ liquide phase during the sintering. Samples with 2 mol% $SiO_2$ has the resistivity of $202{\Omega}cm$ and the resistivity jump of 3.28. It is expected that $SiO_2$ doped $BaTiO_3$ based PTC ceramics can be used for multilayered PTC thermistor due to the resistance to the sintering in reduced atmosphere.

적층 PTC 써미스터의 전기적 특성에 대한 재산화의 영향

전명표,Chun, Myoung-Pyo 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.2

The alumina substrates that Ni electrode was printed on and the multi-layered PTCR thermistors of which composition is $(Ba_{0.998}Ce_{0.002})TiO_3+0.001MnCO_3+0.05BN$ were fabricated by a thick film process, and the effect of re-oxidation temperature on their resistivities and resistance jumps were investigated, respectively. Ni electroded alumina substrate and the multi-layered PTC thermistor were sintered at $1150^{\circ}C$ for 2 h under $PO_2=10^{-6}$ Pa and then re-oxidized at $600{\sim}850^{\circ}C$ for 20 min. With increasing the re-oxidation temperature, the room temperature resistivity increased and the resistance jump ($LogR_{290}/R_{25}$) decreased, which seems to be related to the oxidation of Ni electrode. The small sized chip PTC thermistor such as 2012 and 3216 exhibits a nonlinear and rectifying behavior in I-V curve but the large sized chip PTC thermistor such as 4532 and 6532 shows a linear and ohmic behavior. Also, the small sized chip PTC thermistor such as 2012 and 3216 is more dependent on the re-oxidation temperature and easy to be oxidized in comparison with the large sized chip PTC thermistor such as 4532 and 6532. So, the re-oxidation conditions of chip PTC thermistor may be determined by considering the chip size.

고주파 유전체 세라믹 (Ca_0.7Sr_0.3)_m(Ti_yZr_1-y)O₃의 전기적 특성 및 미세구조

전명표,박명성,강경민,남중희,조정호,김병익,Chun, Myoung-Pyo,Park, Myoung-Sung,Kang, Kyung-Min,Nam, Joong-Hee,Cho, Jeong-Ho,Kim, Byung-Ik 한국결정성장학회 2010 韓國結晶成長學會誌 Vol.20 No.1

고주파 유전체 세라믹 $(Ca_{0.7}Sr_{0.3})_m(Ti_yZr_{1-y})O_3$ 의 미세구조 및 전기적 특성에 대한 Ti 이온 및 몰비의 영향을 조사하였다. $CaZrO_3$의 Zr 위치에 Ti 이온의 치환은 세라믹 소체의 소결밀도 및 미세구조에 큰 영향을 미친다. Zr 위치에 Ti 이온의 치환량 증가에 따라, 소결밀도는 급격히 증가하고, 몰비 m=1.01에서 치밀한 미세조직이 얻어졌다. 한편, 몰비 m=0.99 조성에 대해서는 Ti 치환량이 증가하여도 소결밀도 및 미세구조는 거의 변화가 없이 일정하였다. Ti 치환량 증가에 따라 TCC (temperature coeITicient of capacitance) 곡선은 시계방향으로 회전하여 몰비 m=0.99, 1.01 조성에 대해 COG 특성을 만족하였다. $CaZrO_3$의 TCC 및 소결특성 제어를 위해서는 Ti 치환량이 몰비보다는 효과적임을 보여준다. The effects of mole ratio(A/B) m and Ti-ion on the dielectric properties and microstructure of the microwave dielectric ceramics $(Ca_{0.7}Sr_{0.3})_m(Ti_yZr_{1-y})O_3$ were investigated. Ti ions substituted on Zr-sites in these modified $CaZrO_3$ composition strongly affect the sintering density and microstructure of the fired ceramic body. With increasing the amount of Ti substituted on Zr-sites, the sintered density rapidly increased and the dense microstructure was obtained for the compositions having mole ratio of 1.01, whereas the sintered density and microstructure are nearly constant with the content of Ti-ion for the compositions having mole ratio of 0.99. With increasing the content of Ti ion, the curve of TCC (Temperature Coefficient of Capacitance) as a function of temperature rotated clockwise and satisfied the COG characteristics for both of compositions with mole ratio of 0.99 and 1.01. The content of Ti ion seems to be more effective than mole with respect to the controlling of firing and TCC.

적층 PTC 서미스터

전명표,Jeon, Myeong-Pyo 한국전기전자재료학회 2014 전기전자재료 Vol.27 No.6

New Lead-free Piezoelectric Ceramics in Ternary AgNbO3-NaNbO3-KNbO3 Solid Solutions

조정호,전명표,남중희,한규석,김병익 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.41

0.2AgNbO3-0.8(xNaNbO3-yKNbO3) powders were synthesized by using the solid state reaction method under an air atmosphere. In order to suppress the direct reaction between AgNbO3 and KNbO3, we prepared the AgNbO3-NaNbO3 compound as a first priority. The AgNbO3-NaNbO3compound was then reacted with KNbO3 at 850 ℃ ~ 1050 ℃ for 5 h. Due to the replacement of Na+ ions by K+ ions, a perovskite structure with an orthorhombic symmetry was revealed, but no major structural changes were observed for all investigated compositions. The electromechanical coupling factors (kp) and the piezoelectric constants (d33) were in the range of 37 ~ 40% and 110 ~ 123 pC/N, respectively. We observed no drastic increase of the properties due to coexistence of two phases as Pb(Zr,Ti)O3.

세라믹(BNT)-폴리머(LCP) 복합체 제조 및 유전특성

박명성,전명표,조정호,남중희,최병현,남산,Park, Myoung-Sung,Chun, Myoung-Pyo,Cho, Jung-Ho,Nam, Joong-Hee,Choi, Byung-Hyun,Nahm, Sahn 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.11

In this research, the composites (100-x)LCP-xBNT (x = 0, 10, 20, 30, 40 vol.%) were fabricated with thermoplastic LCP(Liquid Crystal Polymer) and BNT($BaNd_2Ti_4O_{12}$) which is a high frequency dielectric material. Their dielectric properties, mechanical strength and microstructure were investigated by Impedance analyser, Instron and SEM. In order to fabricate LCP-BNT composites, LCP resin was put into the twin screw type mixer($310^{\circ}C$), melted by keeping for 10 min. After that, BNT filler was dispersed with melted LCP resin for 15 min. in the mixer. For measuring the dielectric properties and mechanical strength, Composite specimens were made by pressing composite granule (LCP-BNT) with 7 ton in the mold at $310^{\circ}C$. With increasing the BNT content (0~40 vol.%) of the composite, Its dielectric constant increased, dielectric loss and flexural strength decreased. The dielectric constant and flexural strength of composites with 20~30 vol.% of BNT filler are 4.1~6.0 and 35~55 MPa respectively. BNT/LCP composite is the potential substrate material for the high frequency application.