• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.196-198
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• 1994

The dielectric and electrical properties of $Pb(Mg_{1/3}Nb_{2\3})O_3-PbTiO_3-BaTiO_3$ have been investigated. Perovskite crystalline phase of the specimens are confirmed by XRD at $1270^{\circ}C$. The curie temperature is around $40^{\circ}C$ with the amount of $BaTiO_3$ and $PbTiO_3$. Every specimens shows the slim loop hysteresis curves which is electrostrictive characteristic. The strain vs. applied voltage characteristics exhibits nonlinear relationship, and the specimen of 0.85PMN-0.125PT-0.025BT shows the largest strain.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.9
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• pp.720-725
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• 2001

In this study, Pb(La,Ce)Ti $O_3$ ceramics were manufactured for 20 MHz resonator application. Electromechanical coupling factor( $k_{t}$, $k_{t3}$, mechanical quality factor( $Q_{mt}$ , $Q_{mt3}$ and dydnamic range (D.R) of thickness vibration mode were measured as the variations of $\ell$/t(length/thickness) ratio of ceramic substrates. Mechanical quality factor( $Q_{mt3}$) and dynamic range of third overtone thickness vibration mode showed the highest value of 2,773 and 52.22dB at specimen S4($\ell$/t=12), respectively. The excellent temperature stability of resonant frequency suitable for resonator application was shown, regardless of thermal shock.k.ock.k.

• Journal of the Korean Ceramic Society
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• v.37 no.3
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• pp.256-262
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• 2000

The dielectric properties of complex perovskite ($Pb_{1-x}Ca_{x}$)($Fe_{0.5}Ta_{0.5}$)$O_{3}$ with >($0.5{\le}x{\ge}0.65$ were investigated at microwave frequencies. Dilectric constant decreased with increasing Ca content, and was directly proportional to the cube of average ionic ra야 of A-site. For the specimen of x=0.6 sintered at $1250^{\circ}C$ for 3 h in air, dielectric constant (k) of 63, QF of 11000 GHz, and the temperature coefficient of resonant frequency(TCF) of -14ppm/$^{\circ}C$ were obtained. As Ca content increased, TCF of the specimen negatively increased due to the reduction of the tolerance factor(t). Changes in intrinsic loss with varying Ca content was investigated by the infrared reflectivity spectra ranging 50 to 4000 $cm^{-1}$, which were calculated by the Kramers-Kronig analysis and classical oscillator model. The relative tendency of microwave dielectric properties of the ($Pb_{1-x}Ca_{x}$)($Fe_{0.5}Ta_{0.5}$)$O_{3}$ specimens calculated from the reflectivity data were in good agreement with the results by the post resonant method.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.300-304
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• 1999

To tap the feasibility of exploiting the 2$^{nd}$ phases as flux-pinning centers in the (Bi,Pb)$_2Sr_2Ca_2CuO_{10}$ superconductor, the size and the distribution of the precipitates have been controlled by changing reaction temperature and time, oxygen partial pressure Po$_2$ and annealing condition. Various annealing heat treatments were also conducted on the as-received 61 filament Bi-2223 tapes with Bi$_{1.8}Pb_{0.4}Sr_2Ca_{2.2}Cu_3O_8$ starting composition and annealed specimen were analyzed with XRD, SEM, EDS and TEM.. The grain size of (Ca,Sr)$_2$(BiPb)O$_4$ or Bi$_{0.5}Pb_3Sr_2Ca_2CuO_{\delta}$ was controllable by optimizing the heat treatment condition and critical current density (J$_c$) showed dependence on the size of the 2$^{nd}$ phases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.446-450
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• 2001

In this study, microstructural and electrical properties of (Pb)(La,Nd)$TiO_3$ cerramics were investigated as a function of CuO addition. Taking into consideration Tc of $325^{\circ}C$, dynamic range of 49dB( at the wafer form) and density of $7.71g/cm^{3}$, it can be concluded that the specimen S2 sintered at $1200^{\circ}C$ is the best for the resonator application, Dynamic characteristics of energy-trapped 20MHz SMD type resonator as a function of internal dot size variation were also investigated. Dynamic range characteristics showed the highest value of 60.72dB at S2-4(dot size 1.13mm).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.446-450
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• 2001

In this study, microstructural and electrical properties of (Pb)(La,Nd)TiO$_3$ ceramics were investigated as a function of CuO addition. Taking into consideration Tc of 3$25^{\circ}C$, dynamic range of 49dB( at the wafer form) and density of 7.71g/㎤, it can be concluded that the specimen S2 sintered at 120$0^{\circ}C$ is the best for the resonator application. Dynamic characteristics of energy-trapped 20MHz SMD type resonator as a function of internal dot size variation were also investigated. Dynamic range characteristics showed the highest value of 60.72dB at S2-4(dot size 1.13mm).

• Korean Journal of Materials Research
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• v.12 no.2
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• pp.160-165
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• 2002

High-frequency dielectric and microwave absorbing properties have been investigated in ferroelectric materials (BaTiO$_3$(BT), (1-x)Pb$Mg_{\frac{1}{3}}Nb_{\frac{2}{3}}$)O$_3$-xPbTiO$_3$(PMN-PT), (1-x)Pb$Mg_{\frac{1}{3}}Nb_{\frac{2}{3}}$O$_3$-xPb(Zn_{\frac{1}{3}}Nb_{\frac{2}{3}}$)O$_3$(PMN-PZN) for the aim of thin microwave absorbers in the frequency range of mobile telecommunication. The specimenns are prepared by conventional ceramic processing and complex permittivity has been measured by transmission/reflection method. The ferroelectric materials show high dielectric constant and dielectric loss in the microwave range and their domiant loss mechanism is considered to be domain wall relaxation. The microwave absorbance of BT 0.9PMN-0.1PT, and 0.8PMN-0.2PZN specimen (determined at 2) are found to be 99.5% (at a thickness of 4.5 mm), 50% (2.5 mm), and 30% (2.5 mm), respectively. It is suggested that PMN-PT or PMN-PZN ferroelectrics are good candidate materials for the spacer of λ/4 absorber. The use of ferroelectric materials is effective in reducing the thickness of absorber with their advantage of high dielectric constant.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.471-477
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• 1996

During Bi(Pb)-Sr-Ca-Cu-O superconductor wire fabrication the effect of the initial packing density on the final characteristics of superconductor wire was systematically studied. To increase the powder packing density with uniform distribution of superconducting core a billet insertion method processed by CIP was applied instead of the commonly used vibration and ramming method of powder insertion into silver sheath. Compared with the vibration and ramming method the billent insertion technique processed by CIP cause the 30% incre-specimen with 130${\mu}{\textrm}{m}$(core thickness : 45 ${\mu}{\textrm}{m}$)and 5.24 mm width processed at 84$0^{\circ}C$for 200hrs. shows specimen with 130${\mu}{\textrm}{m}$ (core thickness ; 45${\mu}{\textrm}{m}$)and 5.24 mm width processed at 84$0^{\circ}C$ for 200 hrs. shows maximum 34A for Ic and 16, 700 A/cm2 for Ic measured at 77K and 0T. Also the sample rolled 3 times shows maximum 7, 2A for Ic and 11, 000 A/cm2 for 77K and 0T. Based on X-ray experimental results the formation of Bi-2223 and texture were significantly well developed at the interface between the superconducting core and silver sheath as compared with those of the interior area of superconducting core.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.759-761
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• 1992

$0.10Pb(Sb_{1/2}Sn_{1/2})O_3-0.25PbTiO_3-0.65PbZrO_3+MnO_2(0.18mol%)$, NiO(0.15mol%) temary compound ceramics won fabricated by the mixed-oxide method. Noise properties of the pyroelectric infrared sensor were investigated with particle size of the raw materials and gain size of the specimens. Particle size were decreased and sintered density, voltage resposivity were increased with increasing the ball-mill times. The specimen ball-milled for a 80[hr] showed a good pop-corn noise properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.19-24
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• 2001

In this study, Pb(La Ce)$TiO_3$ composition ceramics were manufactured for 20 MHz resonator application. Electromechanical coupling factor, mechanical quality factor and dynamic range of thickness vibration mode were measured as the variations of L/T(length/thickness) ratio of ceramic substrats. Mechanical quality factor and dynamic range of third overtone thickness vibration mode showed the highest value of 2,773 and 52.22 dB at specimen S4(l/t=12), respectively. The excellent temperature stability of resonant frequency suitable for resonator application was shown, regardless of thermal shock.