• 한국세라믹학회지
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• 제24권6호
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• pp.586-592
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• 1987

The role of the strain energy and phase stability in the diffuse phase transition have been investigated in the highly disordered solid solution, (Pb1-xBax)(Zr0.4Ti0.6)O3 (0.2 x 0.4). X-ray diffraction analysis indicates that tetragonality (c/a) decreases with the increasing Ba content. Also as the Ba content increases, phase transition becomes more diffuse and at the same time dielectric relaxation as a function of measured frequencies in the 1KHz-10MHz range occurs very pronouncedly. In the Ba content range, 0.2 x 0.35, hysteresis loops are routinely observed and the loop is observed to narrow shape as the Ba content increases but becomes very slim at 40mol% Ba content. Moreover thermal analysis shows that there is no abrupt change in the thermal expansion coefficient below the apparent transition temperature at which dielectric constant becomes maximum. From the above results, it has been concluded that creation of the strain energy due to the distorthion that occurred during the phase transition suppresses diffuse phase transition.

• 한국세라믹학회지
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• 제35권5호
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• pp.512-520
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• 1998

PLZT(7.5/70/30) was initially a cubic phase having diffuse phase transition at high temperatures. Sn-sub-stitution for PLZT(7.5/70/30) underwent an irreversible phase transition from cubic to rhom-bohedral structure. However PLZTS(7.5/70/30/y=5 & 10) could be reversibly switched from paraelectric to ferroelectric phase under electric field without showing a significant change in crystal structure. With in-creasing the amount of Sn-substitution the P-E behaviors of the PLZTS became more antiferroelectric which was similar to the effect of La-substitution of PLZT. Our study may suggest that Sn-substitution ef-fectively weakens a formation of long-range order between polar Ti-or Zr- containing octahedra which greatly affects strain properties.

• 한국세라믹학회지
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• 제32권5호
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• pp.635-641
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• 1995

The effects of A-site substitution with alkaline-earth ions (Ca, Sr and Ba) on the perovskite-phase formation and dielectric properties for Pb1-xMx(Zn1/3Nb2/3)O3 (0.0 x 0.5)-based relaxors were studied. Considerable improvements in the sinterability and the extent fo perovskite formation were observed with increasing the A-site substitution (x) and sintering temperature. The maximum dielectric permittivity appeared at x=0.1 for Sr and Ba substitutiion, while the relative dielectric permittivity was almost invariant in the case of Ca ion substitution. Curie temperature decreased with increasing relative amount of Sr and Ba ions but was almost invariant in case of Ca ion substitution. With increasing the amount of x, the diffuseness parameter ($\delta$) increased but the maximum dielectric constant decreased, demonstrating an enhanced diffuse phase transition (DPT) in the presence of alkaline-earth cations.

• 한국세라믹학회지
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• 제28권12호
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• pp.969-974
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• 1991

The influences of A(Cu1/3Nb2/3)O3(A=Pb, Ba and Sr) on the ferroelectric-paraelectric phase transition of BaTiO3 ceramics has been investigated. The tetragonality of crystal structure decreased with increasing A(Cu1/3Nb2/3)O3 content at room temperature. A linear correlation between Curie point and the tetragonality of lattice was not observed. In all three systems the variation of Curie point with the mole fraction showed similar tendency that the Curie point decreased at lower mole fraction but gradually increased in the region of higher mole fractions, Diffuse phase transitions were observed at higher mole fractions. The variation of Curie points could be explained by internal stress and Jahn-Teller distortion of BO6 due to Cu2+, and it was thought that the diffuse character of phase transition was caused by compositional fluctuation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1989년도 춘계학술대회 논문집
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• pp.107-109
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• 1989

Based on the ferroelectric microstructural residual stress model, the relation between grain size and residual elastic energy was proposed. It was found that the residual elastic energy increased with decreasing grain size by modeling and DSC results. This residual elastic energy change with grain size which induce the phase transituion mode change was the cause of a diffuse phase transition in small grain size.

• 한국진공학회지
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• 제17권2호
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• pp.148-155
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• 2008

PMN계 강유전체의 MPB 조성과 공존영역의 확산성을 이해하기 위해 유전 및 초전 특성을 분석하였다. PMN-PT계는 완만한 상전이를 보였으며, 이는 하나의 상유전과 2개의 강유전상이 공존함을 의미한다. 즉, 0.7PMN-0.3PT 조성 부근에서 능면정계와 정방정계의 공존 영역인 조성변태 상경계를 확인하였으며, 이들 조성은 연속적으로 능면정계$\rightarrow$정방정계$\rightarrow$입방정계로 상전이를 하였다. PT>0.325인 조성들은 측정된 진동수 범위에서 진동수 의존성을 보이지 않는 단일상의 강유전 특성을 보였으며, PMN>0.7인 조성들은 큰 진동수 의존성과 확산상전이의 전형적인 완화형 강유전 특성을 보였다. PMN-PT계의 조성변태 상경계 조성들은 우수한 유전 및 초전특성을 나타내었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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• pp.25-33
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• 1994

Temperature dependences of the remanent polarization $P_{\gamma}$/(T), effective birefringence ㅿｎ(T). dielectric constant K(T) and quadratic electro-optic coefficient R(T) of the two-stage sintered xBa(La$_{1/2}$Nb$_{1/2}$)O$_3$Pb$(Zr_{y}Ti_{1-y})O-{3}$(x=0.085, 0.09, 0.40$\leq$y$\leq$0.70)ceramics were investigated. Increasing the PbZrO$_3$ contents, the crystal structure of a specimen was varied from tetragonal and rhombohedral to cubic, and the phase transition was showed a diffuse phase transition(DPT) characteristics. Especially. in the compositions which located on the PE-FE phase boundary were showed a discrepancy between curie temperature and temperature range which a macroscopic polarization and a effective birefringence were disappeared.

• E2M - 전기 전자와 첨단 소재
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• 제8권2호
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• pp.190-195
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• 1995

Temperature dependences of the dielectric constant K(T), remanent polarization $P_{r}$, (T), effective birefringence overbar .DELTA.n(T), transmitted light intensity and quadratic electro optic coefficient R(T) of the two-stage sintered xBa(L $a_{1}$2/N $b_{1}$2/) $O_{3}$-(1-x)Pb(Z $r_{y}$ $Ti_{1-y}$) $O_{3}$(x=0.085, 0.09, 0.40.leq.y.leq.0.70) ceramics were investigated. Increasing the PbZr $O_{3}$ contents, the crystal structure of a specimen was changed from a tetragonal phase to a rhombohedral and cubic phase, and the phase transition was showed a diffuse phase transition(DPT) characteristics. In the compositions which located on the PE-FE phase boundary, the discrepancy was observed between the Curie temperature and temperature which a microscopic polarization and effective birefringence were disappeared.red.d.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1998년도 추계학술발표강연 및 논문개요집
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• pp.55-55
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• 1998

• 한국결정성장학회지
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• 제30권3호
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• pp.110-116
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• 2020

MLCC(Multi-Layer Ceramic Capacitor)의 유전체 층에 사용되는 BaTiO₃ 입자는 안정한 TCC(Temperature Characteristics of Capacitance) 거동을 갖기 위해 core/shell 구조를 갖는다. 지금까지 shell의 특성은 core/shell 구조의 전체 특성에서 유추해 왔다. 이는 core/shell 구조가 겨우 수 ㎛의 작은 크기로 shell 특성만 구별해서 측정하기가 어렵기 때문이다. 본 실험에서는 micro-contact법을 이용하여 확산쌍 시편의 계면에 형성된 확대된 core/shell 구조에 Pt 전극을 증착하여 35~135℃ 에서 shell 영역의 독립적인 TCC 거동을 측정하였다. 그 결과, 65℃에서 최대 유전율 값을 갖는 완만한 피크의 확산 상전이(Diffusion Phase Transition) 거동인 core의 특성과 구별되는 거동을 관찰하였으며, 이는 core/shell 구조의 온도-유전거동을 묘사하는 모델링에서 실험 자료로 활용될 것으로 본다.