• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.967-976
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• 1995

The possiblity of the existence of a spontaneous relaxor-normal ferroelectric transition was proposed and examined using 1~5 mol% PbZrO3-doped Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) systems having tetragonal symmetry at rom temperature. On cooling, the system with 60mol% Pb(Ni1/3Nb2/3)O3 underwent a spontaneous transition from a relaxor to a normal ferroelectric state. A microscopic examination demonstrates that the relaxornormal ferroelectric transition corresponds to a micro-macro domain switching accompanied with thermoelastic martensitic transformation. The long-range macrodomains below the transition temperature were characterized by twinlike 90$^{\circ}$macrodomains with tetragonal symmetry. The relaxor-normal ferroelectric transition was further correlated with the rhombohedral-tetragonal first-order structural transition.

• Nuclear Engineering and Technology
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• v.43 no.5
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• pp.421-428
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• 2011

The out-of-pile mechanical performance and microstructure of recrystallized Zr-1.5 Nb-S alloy was investigated. The strength of the recrystallized Zr-1.5Nb-O-S alloys was observed to increase with the addition of sulfur over a wide temperature range, from room temperature up to $300^{\circ}C$. A yield drop and stress serrations due to dynamic strain were observed at room temperature and $300^{\circ}C$. Wavy and curved dislocations and loosely knit tangles were observed after strained to 0.07 at room temperature, suggesting that cross slip is easier. At $300^{\circ}C$, however, dislocations were observed to be straight and aligned along the slip plane, suggesting that cross slip is rather difficult. At $300^{\circ}C$, oxygen atoms are likely to exert a drag force on moving dislocations, intensifying the dynamic strain aging effect. Oxygen atoms segregated at partial dislocations of a screw dislocation with the edge component may hinder the cross slip, resulting in the rather straight dislocations distributed on the major slip planes. Recrystallized Zr-Nb-S alloys exhibited ductile fracture surfaces, supporting the beneficial effect of sulfur in zirconium alloys. Oxidation resistance in air was also found to be improved with the addition of sulfur in Zr-1.5 Nb-O alloys.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.13-16
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• 1994

In this paper, xPb(Zn$_{1/3}Nb_{2/3}$)$O_3$-yPbTiO$_3$-zPbZrO$_3$-(0.5wt%)MnO$_2$ ceramics were fabricated by the mixed oxide method sintered at $1250^{\circ}C$ for 2[hr] and then the deielectric, electromechanical coupling factor($K_{p}$ and mechanical coupling factor(Qm) properties were investigated. In 0.1PZN-0.45PT-0.45PZsample, dielectric properties and electromechanical coupling factor were 829 and 29%. In the case of 0.5PZN-0.45PT-0.50PZ sample, that was 101 according to mechanical quality facotr. molphotropic phase boundary(MPB) certained area which $PbTiO_3$addition quatity 40∼50[㏖%].

• Electrical & Electronic Materials
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• v.1 no.2
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• pp.152-161
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• 1988

Pb(Zr, Ti)O$^{3}$-Pb(Mg, Nb)O$^{3}$계에 MnO$_{2}$첨가량을 변화시켜 소결성, 미세구조, 유전상수, 비저항 및 압전특성에 미치는 영향을 XRD, EDAX 및 SEM을 이용하여 미세구조를 관찰하고 실험을 통하여 전기적 성질에 미치는 영향을 밝혔다. 비저항의 변화없이 그레인 성장이 억제되는 $MnO_{2}$의 첨가량은 0.4wt%이었으며 이때 분말의 합성이 촉진되어 소성된 시편의 밀도가 증가하였다. 그러나 고상반응의 범위를 벗어나는 과잉 $MnO_{2}$는 편석이 되어 그레인 경계상에 모임이 확인되었고 또한 기공을 형성하여 밀도를 낮추었다. $Mn^{+4}$는 $Mg^{+2}$ 와 치환되어 페로브스카이트 구조의 "A" 결핍을 유발하였으며 이것이 비저강을 감소시키는 원인으로 밝혀졌다.감소시키는 원인으로 밝혀졌다.

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.369-374
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• 2002

To investigate the corrosion behavior of Zr-1.0Nb-xSn (x=1.0, 1.5, 2.0 and 2.5wt. %)alloy system, the corrosion tests of Zr-1.0Nb-xSn alloys were carried out in steam at $400^{\circ}C$ for 125 days and in 70ppm LiOH solution at $360^{\circ}C$ for 180 days. The matrix microstructures of the test specimens were analyzed using TEM and the oxide structures on the test specimens were analyzed using XRD. It was found from the analyses that the more Sn content the alloy had, the faster it was corroded and with the increase of Sn content in the alloy the fraction of $t-ZrO_2$ to $m-ZrO_2$ was decreased. It was also found that the alloys having more Sn showed more dislocation density than those having less.

• Journal of the Korean Ceramic Society
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• v.24 no.6
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• pp.537-542
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• 1987

The microstructure and electrical properties of Pb[(Sb1/2 Nb1/2)0.08 Zr0.49 Ti0.48]O3 with MnO2 addition have been investigated in this work. The amount of MnO2 addition was 0, 0.4, 0.8, 1.2, 2.0 wt%, respectively. The soild solution range of MnO2 that assumed in this composition according to thevariations of micro-structure and electrical properties was 0.4-0.8 wt%.

• Electrical & Electronic Materials
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• v.1 no.2
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• pp.162-167
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• 1988

본 논문에서는 Pb(Sn$_{1}$7/Mn$_{2}$7/Nb$_{4}$7/)O$_{3}$- Pb(Zr, Ti)O$_{3}$계에 La$_{2}$O$_{3}$를 첨가하여 그양에 따른 압전일 전기력 성질의 변화를 고찰하였다. La$_{2}$O$_{3}$ 첨가량의 증가에 따라 유전상수, 압전 d상수, 유전손실, 비저항 등은 증가하였으나 경시 변화량은 오히려 감소하였다.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.523-531
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• 1988

The dielectric and piezoelectric properties with compositions in Pb(Ni1/3Nb2/3)O3-PbTiO3-PbZrO3-(PNN-PT-PZ)solid solution ceramics were investigated. In this study, the compsition ranges were 30 PNN 45mole%, 20 PT 50mole% and 50 PZ5mole%. As PT fraction were increased the grain size was increased and the fired density was decreased, but the changes of PNN fraction had no effect on the grain size. The Curie temperature was increased when PT and PNN fraction were increased. The displacement was increased but had a great hysteresis loss when PT fraction was increased. In morphotropic phase boundary, the maximum piezoelectric and electromechanical coupling factor were indicated. Morphotropic phase boundary(MPB) was 34 PT 36mole% in chang of compositions.

• Journal of the Microelectronics and Packaging Society
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• v.2 no.2
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• pp.31-40
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• 1995

Donor dopant로 WO3, Ta2O5 및 Nb2O5를 첨가한 Zr0.8Sn0.2TiO4 세라믹스의 유전상수 $\varepsilon$r 품 질계수 Q 및 공진주파수의 온도계수 rf에 대하여 연구하였다. 139$0^{\circ}C$에서 32시간 소결시 donor dopant 첨가량에 따른 ZST의 유전상수는 소결밀도의 변화 거동과 잘 일치하였다. 5.5 GHz에서 측정 한 ZST의 품질계수 Q는 ~0.5 mol% WO3 Ta2O5 및 Nb2O5 첨가에 의해 6800에서 8500 정도로 증가 하였다. ZST의 $\tau$f는 0.3 mol%까지의 WO3 첨가량 증가에 따라 0 ppm/$^{\circ}C$에서 -4.6 ppm/$^{\circ}C$까지 음 의 값으로 직선적으로 감소하였으며 0.4 mol% 범위의 Ta2O5 및 Nb2O5 첨가에 의해 -7 ppm/$^{\circ}C$ 까지 직선적으로 감소하였다.

• Journal of the Korean Ceramic Society
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• v.23 no.3
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• pp.21-26
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• 1986

In this study the system of $Pb(Mn_{1/3} Nb_{2/3})O_3-PbTiO_3-PbZrO_3$ piexoelectric ceramics was made in the radial mode disk and attenuation characteristic of the desinged ladder type filter was investigated. What is more temperature dependance of resonant frequency and variation of resonant frequency was examined by chan-ging the electrode diameter of piezoelectric resonator. (A Group : De=11mm, B Group : De=7.5mm and C Gro-up : De=5.5mm) Upon investigation it was the following. The center frequency of A, B and c filter showed up in the 200KHz, 270KHz and 380KHz respectively. As the electrode diameter decreased center frequency in creased abruptly. As the Co_2/Co1 increased attenuation characteristics and selectivity was improved. As the x=50. resonant frequ-ency invaried with variation of temperature.