• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1466-1468
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• 1994

In this paper Dielectric and strain properties of (1-x-y)PMN-yPT-xST Ceramics have been investigated as a function of the amount of $SrTiO_3(ST)$. The $SrTiO_3$ content is ranged from 0.01-0.06(wt%). As the amount of ST is increased, dielectric constant has a maximum value at 0.05 mol composition. The Curie temperature is decreased linearly with increasing ST composition and Polarization properties have been investigated. Coercive field and ramnant polarization has a maximum value at 0.01mol composition.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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• pp.5-8
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• 1994

In this paper, Dielectric and strain properties of (1-x-y)PMN-yPT-xST Ceramics hale been investigated as a function of the amount of SrTiO$_3$(ST). The SrTiO$_3$ content is ranged from 0.01-0.05(wt%). As the amount of ST is increased, dielectric constant has a maximun value at 0.05 mol% composition. The Curie temperature is decreased linearly with increasing ST composition and Polarization properties have been investigated. Coercive field and remnant polarization has a maximum value at 0.01mo1% composiion.

• 한국주조공학회지
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• 제24권4호
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• pp.231-237
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• 2004

Bake hardenable steel utilizes the phenomenon of strain aging to provide an increase in the yield strength of formed components. An increase of the carbon content will improve the bake hardening response: more solutes are available to pin mobile dislocations and to form the clusters more rapidly. But aging resistance decrease as increasing solute carbon. In order to under-stand the compatibility between bake hardenability and aging resistance. The optimum solute carbon control methods during manufacture should be determined. In this paper, the effect of continuous heat cycle conditions such as soaking temperature, rapid cooling start temperature, cooling rate on BH(Bake Hardenability), AI(Aging Index), YP-El(Yield Point Elongation) and other mechanical properties have been investigated. and following results were obtained. In the case of soaking temperature, BH increases with higher soaking temperature because of NbC $dissolution(830^{\circ}C)$, Therefore the solute carbon and BH at $850^{\circ}C$ and $870^{\circ}C$ are higher than these at $810^{\circ}C$. But BH at $870^{\circ}C$ is a little lower than that at $850^{\circ}C$ owing to the ferrite grain size. The measurement of amount of dissolution C using IFT(Internal Friction Test) can explain the relation of solute carbon and BH.

• 한국추진공학회지
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• 제13권3호
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• pp.34-40
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• 2009

카본슬러리 연료 제조 시 카본의 분산안정성에 미치는 공정변수의 영향을 조사하였다. 카본슬러리연료의 분산안정성은 위치별 입도분석, 카본함량 분석, 그리고 원심분리 후 분산상태 관찰을 통해서 측정하였다. 여러 종류의 첨가제를 적용한 결과, NB463S84 사용시 분산성과 분산안정성이 가장 우수한 것을 알 수 있었다. NB463S84와 비슷한 작용기를 가지는 PIBSI를 합성하였으며, 이를 카본슬러리 연료에 적용하여 유사한 분산안정도를 얻었다. 끝으로 g 규모에서 얻은 제조 조건을 kg 규모 제조에 적용하여 카본슬러리 연료의 실용화 가능성을 확인하였다.

• 한국전기전자재료학회논문지
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• 제27권5호
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• pp.292-296
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• 2014

We investigated the effect of Ta doping on the dielectric and piezoelectric properties of lead-free $(K_{0.5}Na_{0.5})NbO_3$ ceramics prepared using a conventional ceramic processing. X-ray diffraction analysis revealed that Ta was perfectly substituted into Nb-sites in the range of 0 to 20 at%. As Ta content in the KNN increased, the sinterability of KNN ceramics was significantly degraded while the Ta doping enhanced the piezoelectric constant $d_{33}$, planar mode piezoelectric coupling coefficient ($k_p$), and electromechanical quality factor ($Q_m$). The highest values for $d_{33}$, $k_p$, and $Q_m$ was found to be 156 pC/N, 0.37, and 155, respectively.

• 한국전기전자재료학회논문지
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• 제25권9호
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• pp.702-710
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• 2012

Eco-friendly $(Na,K)NbO_3$ (NKN)-based piezoelectric ceramic materials were fabricated by conventional ceramic method for shear mode piezoelectric energy harvesting application. $NKN-LiTaO_3$ (LT) based compositions were adopted for the high $d_{15}{\times}g_{15}$ which is proportional to harvested energy density. The composition $0.935(Na_{0.535}K_{0.485})NbO_3-0.065LiTaO_3$ was found to be lie on the boundary of tetragonal and orthorhombic phases. With reducing Ta content, the dielectric constant decreased gradually while maintaining high $d_{15}$, which resulted in increased $d_{15}{\times}g_{15}$. The composition $0.935(Na_{0.535}K_{0.485})NbO_3-0.065Li(Nb_{0.990}Ta_{0.010})O_3$ was found to possess excellent piezoelectric and electromechanical properties ($d_{15}{\times}g_{15}=29\;pm^2/N$, $d_{15}$ = 417 pC/N, $k_{15}$ = 0.55), and high curie temperature ($T_c=455^{\circ}C$).

• 한국분말재료학회지
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• 제17권4호
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• pp.289-294
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• 2010

For the aim of low-temperature co-fired ceramic microwave components, sintering behavior and microwave properties (dielectric constant ${\varepsilon}_r$, quality factor Q, and temperature coefficient of resonant frequency ${\tau}_f$) are investigated in $Bi_{18}O(Ca_{0.725}Zn_{0.275})_8Nb_{12}O_{65}$ [BCZN] ceramics with addition of $V_2O_5$. The specimens are prepared by conventional ceramic processing technique. As the main result, it is demonstrated that the additives ($V_2O_5$) show the effect of lowering of sintering temperature and improvement of microwave properties at the optimum additive content. The addition of 0.25 wt% $V_2O_5$ lowers the sintering temperature to $890^{\circ}C$ utilizing liquidphase sintering and show the microwave dielectric properties (dielectric constant ${\varepsilon}_r$ = 75, quality factor $Q{\times}f$ = 572 GHz, temperature coefficient of resonance frequency ${\tau}_f\;=\;-10\;ppm/^{\circ}C$). The estimated microwave dielectric properties with $V_2O_5$ addition (increase of ${\varepsilon}_r$, decrease of $Q{\times}f$, shift of ${\tau}_f$ to negative values) can be explained by the observed microstrucure (sintered density, abnormal grain structure) and possibly high-permittivity $Bi_{18}Zn_8Nb_{12}O_{65}$ (BZN) phase determined by X-ray diffraction.

• The Korean Journal of Ceramics
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• 제6권3호
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• pp.276-279
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• 2000

Ferroelectric properties of $SrBi_2TaNbO_9$ (SBTN) thin films were changed by the amount of Bi content in SBTN. We suggested that the addition of excess Bi into the films could be accomplished by heat-treating $SBTN/Bi_2O_3/SBTN$ heterostructure fabricated by r.f. magnetron sputtering method. Excess Bi composition was controlled by the thickness of the sandwiched $Bi_2O_3$ from 0 to $400\;\AA$. When the SBTN thin films were inserted by $400\;{\AA}\;Bi_2O_3$ layer, $Bi_2Pt$ phase was formed as a second phase in SBTN films, resulting in poor ferroelectric properties. The onset temperature for hysteresis loop can be reduced by heat treating $SBTN/Bi_2O_3/SBTN$ heterostructure. The films with $SBTN/Bi_2O_3(100\;{\AA})/SBTN$ hetero-structure followed by annealing at $650^{\circ}C$ for 30 min show 2Pr and Ec of $5.66\;{\mu}C/\textrm{cm}^2$ and 54 kV/cm, respectively.

• 대한화학회지
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• 제27권4호
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• pp.273-278
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• 1983

합성표준시료를 이용하여 주석슬랙 중 유가금속들인 $Ta_2O_5, Nb_2O_5, TiO_2, SnO_2 $및 $ZrO_2$를 X-선형광분광법으로 정량하였다. 분석시료와 표준시료분말들을 융제인 무수 $Li_2B_4O_7$과 $La_2O_3$를 무게비 15:42:3의 비율로 균일하게 혼합한다. 혼합분말을 $1,150^{\circ}C$에서 30분간 용융하여 유리구슬을 만든다. 이 구슬을 325메쉬 이하로 분쇄하여 수압기를 이용 pellet으로 만들어 시편으로 사용한다. 분석결과들은 다른 분석법에 의해 얻은 값들과 허용오차 범위내에서 잘 일치한다. 또 PTS-H시료에 대한 표준편차가 함량 3.40 %에서 0.12 %로 재현성도 좋음을 보여 주었다.

• 한국세라믹학회지
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• 제38권11호
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• pp.1042-1045
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• 2001

Ba(Zn$_{1}$3/Nb$_{2}$3/) $O_3$-Sr(Zn$_{1}$3/Nb$_{2}$3/) $O_3$계에 대하여 소결 온도 변화와 Zr $O_2$첨가량에 따른 마이크로파 유전특성을 조사하였다. 동일 조성에서 소결 온도가 증가함에 따라 밀도가 향상되고 공진 주파수의 온도계수($ au$$_{f}$)는 감소하는 경향을 보였으나, 유전상수(K)와 품질계수(Q$\times$f)는 커다란 변화가 없었다. 또한 Zr $O_2$첨가량이 증가함에 따라 소결 시편의 밀도가 향상되었고 더불어 유전상수, 품질계수가 증가하는 경향을 보였으며, 공진 주파수의 온도계수가 감소하는 우수한 특성이 나타났다. 특히, 소결온도 1575$^{\circ}C$, 0.6 wt% Zr $O_2$를 첨가했을 때 유전상수가 최대($\varepsilon$$_{r}$=41)로 나타났으며, 공진 주파수의 온도계수는 1.0wt% Zr $O_2$를 첨가했을 때 최소($\tau$$_{f}$=+0.8ppm/$^{\circ}C$)로서 양호한 값을 얻을 수 있었다.었다.