• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.71-74
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• 2000

Pt/Pb$TiO_3$/$SrTiO_3$/p-Si films were prepared by metallo-organic solution deposition(M0SD) method and investigated its structure and ferroelectric properties. Crystallinity of specimen as a funtions of post annealing temperature and the thickness of $SrTiO_3$(STO) buffer layer was studied using XRD and AFM. Based on C-V and P-E curve, $PbTiO_3$(PTO) capacitors showed good ferroelectric hysteresis arising from the polarization switching properties. When the thickness of ST0 buffer layer between PTO and Si substrate was 260 nrn and the post annealing temperature was $650^{\circ}C$, it was showed that production of the pyrochlore phase due to interdiffusion of Si into FTO was prevented. The dielectric constant of FTO thin films calculated from a maximum Cma in the accumulation region was 180 and the dielectric loss was 0.30 at 100 kHz frequency. The memory window in the C-V curve is 1.6V at a gate voltage of 5V.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권9호
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• pp.611-615
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• 1999

Piezoelectric properties of PMN-PZT ceramics with $CeO_2$ impurity were investigated. Mechanical quality factor, $Q_m$ of 1792, 1285 and the electromechanical coupling coefficient, $k_p$ of 0.52, 0.54 were obtained from the specimen with 0.25 and 0.5 mole % $CeO_2$ respectively. Curie temperature was decreased with the addition of $CeO_2$ while the electric coercive field was proportional to the amount of impurity. Based on the system ceramics with 0.5 mole % cerium oxide, a Rosen type piezoelectric transformer was fabricated and tested. Voltage step-up ratios of 230 and 13 were obtained from the transformer at no load and $100 k\Omega$ resistance, respectively. Experimental results showed a potential of the transformer for the practical use coupled with the expected strength increase by the grain size refinement.

• 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.

• 한국분말재료학회지
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• 제17권2호
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• pp.101-106
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• 2010

In this study, we successfully synthesized a nano-sized lanthanum-modified lead-titanate (PLT) powder with a perovskite structure using a high-energy mechanochemical process (MCP). In addition, the sintering behavior of synthesized PLT nanopowder was investigated and the sintering temperature that can make the full dense PLT specimen decreased to below $1050^{\circ}C$ by using $Bi_2O_3$ powder as sintering agent. The pure PLT phase of perovskite structure was formed after MCP was conducted for 4 h and the average size of the particles was approximately 20 nm. After sintered at 1050 and $1150^{\circ}C$, the relative density of PLT was about 93.84 and 95.78%, respectively. The density of PLT increased with adding $Bi_2O_3$ and the specimen with the relative densitiy over 96% were fabricated below $1050^{\circ}C$ when 2 wt% of $Bi_2O_3$ was added.

• 대한전기학회논문지
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• 제44권4호
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• pp.479-482
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• 1995

In this study, to improve sintering condition, anisotropic properties ( $k_{t}$/ $k_{p}$) of electromechanical coupling coefficient and piezoelectric constant $d_{h}$ and $g_{h}$, Mn $O_{2}$ impurity was added to the (P $b_{0.76}$C $a_{0.24}$)[( $Co_{1}$2/ $W_{1}$2/)$_{0.04}$ $Ti_{0.96}$] $O_{3}$ ceramics for application to hydrophone devices. Electromechanical coupling coefficients of the specimen with 1.5 [mol%] Mn $O_{2}$ sintered at 1150.deg. C were $k_{t}$=49% and $k_{p}$ = O, which exibited the highest value in piezoelectric anisotropic properties (kt/kp). Without relations with sintering temperature, the highest value of hydrostatic piezoelectric constant $d_{h}$ & $g_{h}$ were shown at the specimen with 1.5 [mol%] Mn $O_{2}$. Accordingly, the best addition amount of Mn $O_{2}$ was 1.5 [mol%] and proper sintering temperature was 1150.deg. C. Hydrostatic piezoelectric constant values of $d_{h}$=64.52[10$^{-12}$ C/N], $g_{h}$=35.92[10$^{-3}$ Vm/N] in the above condition were effectiely extended for hydrophone applications.pplications.ons.

• 마이크로전자및패키징학회지
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• 제8권2호
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• pp.9-13
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• 2001

$(Ba_{0.5}Pb_{0.5})Nd_2Ti_5O_{14}$(마이크로파 유전체 세라믹스에 borosilicate계 유리를 첨가하여 저온소결 특성과 마이크로파 특성을 조사하였다. Borosilicate계 유리가 2~3 wt% 첨가된 경우 $950^{\circ}C$의 소결 온도에서 소결성이 향상됨과 동시에 품질계수도 놀아지는 것을 확인할 수 있었다. BPNT에 3 wt%의 유리를 첨가함으로써 $950^{\circ}C$에서 유전율은 90에서 75 정도로 약간의 감소를 보였으나 마이크로파 품질계수 (Q$\times$f)는 4500 정도로 잘 유지되었고 공진주파수의 온도계수도 +10 $ppm/^{\circ}C$로서 잘 유지되는 결과를 나타내었다.

• 한국재료학회지
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• 제12권12호
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• pp.911-917
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• 2002

0.5 at% $Na_2$Te-doped ($Pb_{0.7}Sn_{0.3}$)Te and ($Bi_{0.2}Sb_{0.8}$)$_2$$Te_3$ powders were fabricated by mechanical alloying process. 0.5 at% Na$_2$Te-doped ($Pb_{0.7}Sn_{0.3}$)Te powders were charged at one end of mold and ($Bi_{0.2}Sb_{0.8}$)$_2$$Te_3$ powders were charged at the other end of a mold. Then these powders were hot-pressed to form p-type ($Pb_{0.7}Sn_{0.3}$)Te/($Bi_{0.2}Sb_{0.8}$)$_2$$Te_3$ functional gradient materials with the segment ratios (the ratio of ($Pb_{0.7}Sn_{0.3}$)Te to ($Bi_{0.2}Sb_{0.8}$)$_2$$Te_3$ ) of 1:2, 1:1, and 2:1. Power generation characteristics of the ($Pb_{0.7}Sn_{0.3}$)Te/($Bi_{0.2}Sb_{0.8}$)$_2$$Te_3$ were measured. When the temperature difference ΔT at both ends of the specimen was larger than $300^{\circ}C$, the ($Pb_{0.7}Sn_{0.3}$)Te/($Bi_{0.2}Sb_{0.8}$)$_2$$Te_3$ with the segment ratios of 1:2 and 1:1 exhibited larger output power than those of the ($Bi_{0.2}Sb_{0.8}$)$_2$$Te_3$ and 0.5 at% $Na_2$ Te-doped ($Pb_{0.7}Sn_{0.3}$)Te alloys. The maximum output power of the ($Pb_{0.7}Sn_{0.3}$)Te/($Bi_{0.2}Sb_{0.8}$)$_2$$Te_3$ predicted with the measured Seebeck coefficient and the estimated electrical resistivity was in good agreement with the measured maximum output power.

• 한국산학기술학회논문지
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• 제6권6호
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• pp.542-546
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• 2005

연성 크랙의 발생 평가를 위한 J-적분이 충격 하중을 받는 탄소성 3점 굽힘 시험편들에 대하여 연구한다. J-적분을 측정하고 평가하는 실험적인 방법이 연구되었으며 이 결과가 유한 요소법을 이용한 탄소성 이론 해석을 한 값들과 비교하여 거의 일치함을 보였다. 이론적인 수치 해석으로서도 본 연구의 유한 요소 모델로서 J-적분값을 계산할 수 있으며 삼점 굽힘 시험편의 동적 비선형 파괴 실험에 있어서 크랙 입구 개구 변위 (CMOD)에 의하여 J-적분값의 단순 계산이 가능함을 입증하였다. 탄소성 재료의 특성이 여러 가지의 충격 속도들에서 고려된다. J-적분은 충격 실험 동안 얻어진 사진들로부터 직접적으로 측정된 크랙 입구 개구 변위로부터 예측될 수 있다.

• 한국재료학회지
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• 제4권3호
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• pp.334-338
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• 1994

Pb-Sn eutectic bulk specimens을 thermal cycling동안 electronic package의 땜납이 격게되는 변형 조건 즉 $10^{-3}-10^{-5}$/s정도의 낮은 frequency와 0.2-1%정도의 적당한 strain range에서 피로파괴 실험을 했을때, grain boundary sliding과 관련하여 임계면을 따라 일어나는 균열이 5단계에 의해 묘사될 수 있다는 것을 보였음.

• 한국재료학회지
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• 제1권2호
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• pp.71-76
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• 1991

The superconducting powders in $YBa_2Cu_3O_{7-x}$ and Bi-Pb-Sr-Ca-Cu-O system were easily prepared from water in oil type emulsion by loading each cation into the aqueous phase. In $YBa_2Cu_3O_{7-x}$ system, the superconducting orthorhombic phase was formed by calcining at $750^{\circ}C$ for 10h in $O_2$. The size of the superconducting phase powders was submicron. The density of the sintered specimen using this powders was about 95% of the theoretical density and the resistance sharply decreases at about 90K, In Bi-Pb-Sr-Ca-Cu-O system the low Tc phase($(Bi, Pb)_2Sr_2Ca_1Cu_2O_y$) was formed by calcining at $800^{\circ}C$ for 10h in a low oxygen partial pressure of 1/20 atm The shape of clacined powder is thin plate of which size is about $2\mu\textrm{m}$ and thickness is smaller than $\mu\textrm{m}$. It was observed that the high Tc phase ($(Bi, Pb)_2Sr_2Ca_2Cu_3O_y$) was formed by sintering at $850^{\circ}C$ for 30h in oxygen pressure of 1/20 atm without intermediary grinding. The above sintered sample exhibited superconductivity with a Tc(zero)=105K.