• Journal of the Korean Ceramic Society
• /
• v.38 no.7
• /
• pp.639-642
• /
• 2001

전형적인 비저항-온도 특성을 갖는 BaTiO$_3$계 PTC 세라믹을 일반적인 세라믹 공정을 이용하여 제조하였고, 결정립계면에 형성된 전위장벽의 높이를 구하였다. ZnO 바리스터의 전위장벽을 구하기 위해 이용되었던 커패시턴스-전압 관계식과는 다른 새로운 관계식을 제안하였고, 기존의 비저항-온도 관계식을 다소 변경한 관계식을 이용하여 전위장벽을 구하였다. 두 관계식으로부터 구한 전위장벽의 높이는 매우 유사한 값을 보이고 있으며 타 연구자들에 의해 보고된 값과도 잘 일치하고 있다. 비저항-온도 관계식과 커패시턴스-전압 관계식을 이용하여 130-18$0^{\circ}C$ 구간에서 구한 전위장벽의 크기는 각각 0.41-0.76V와 0.36-0.80V이었다.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.03a
• /
• pp.234-234
• /
• 2003

MgTiO$_3$와 ZnTiO$_3$ 같은 ilmenite형 세라믹스는 유용한 유전특성 때문에 MLCC와 RF/microwave 장치와 같은 유전체 세라믹 부품에 사용될 수 있다. 그러나, 이 두 ilmenite형 세라믹스는 저온에서 hexagonal 구조를 띄는 ilmenite 합성에서의 난점들 때문에 LTCC에 사용되기 어려운데, 본 연구에서는 ilmenite형 세라믹스의 합성을 개선시키는데 Mechanically Activated Syntheses법(이하 MAS법)을 이용했다. MAS법으로 합성온도를 낮출 수 있었고 원치 않는 2차상의 형성을 방지할 수 있었으며, LTCC에 이용될 수 있는 분말들의 소결온도를 95$0^{\circ}C$ 이하로 내릴 수 있었다. 또한, MAS법을 이용했을 때와 기존의 방법을 이용했을 때의 여러 특성들을 비교 분석했다.

• The Korean Journal of Ceramics
• /
• v.2 no.2
• /
• pp.89-94
• /
• 1996

Aluminum and zinc titanium silicate sol-gel films were fabricated for application of waveguide and the effect of additions of ZnO and $Al_2O_3$ to binary titanium silicate films was investigated. During firing, the films are densified as they shrunk and their refractive index increases in the range of 1.58-1.83 depending on the film composition. The attenuation of the waveguides is not sensitive to changes in composition except for zinc titanium silicate waveguides which have substantially higher attenuation. However, the increase in the attenuation with aging of the waveguides depend upon the composition of waveuides. The addition $Al_2O_3$ or the reduced $SiO_2$ content in the composition appears to slow the deterioration of the waveguides due to the formation of more stable bonds and increased acidity on the film surface. Also, the wavelength dependence of the attenuation of the waveguides varies with composition. The attenuation of the waveguides except for the $65SiO_2{\cdot}35TiO_2$ composition are not Rayleigh scatter limited, suggesting the absorption loss of the waveguides due to the effects of residual carbon and structural defects in the films.

• Journal of the Korean Ceramic Society
• /
• v.41 no.2
• /
• pp.165-169
• /
• 2004

Microwave dielectric properties and the behavior of low-temperature sintering of $Zn_{1-x}(Li_{1/2}La_{1/2})_xTiO_3$ ($0.01{\leq}x{\leq}0.05$) with 4 wt% $H_3BO_3$ were investigated as a function of $(Li_{1/2}La_{1/2})^{2+}$ content. The sintering temperature of the specimens can be reduced from $1150^{\circ}C$ to $875^{\circ}C$ with the addition of 4 wt% $H_3BO_3$ as a sintering agent. Dielectric constant (K) and Temperature Coefficient of resonant Frequency (TCF) with the substitution of ($(Li_{1/2}La_{1/2})^{2+}$ ion depended on dielectric mixing rule. Quality factor (Qf) depended on density and microstructure. Typically, K of 26.5, Qf of 19,030 GHz and TCF of 7.5 ppm$/^{\circ}C$ were obtained for the specimens with x=0.03 sintered at $875^{\circ}C$ for 3 h.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.23 no.2
• /
• pp.118-123
• /
• 2010

The eco-friendly technologies have been extended as matter of international concern due to various diseases and syndromes according to an environmental pollution. In this study, we have manufactured a ceramic cluster with thick film type for anion generation equipment which is maximized anion but minimized ozone contents generated. To develop the formulation of ceramic cluster, we conducted the $Mg_2SiO_4$ powders doped with 10 vol% glass frits as Na-Zn-B-O system and sintered at $1050^{\circ}C$ for 2 hours in air for starting materials and investigated the matching properties between the Ag-Pd electrode and the starting materials. The sintered sample for the composition of cluster has 6.7 of dielectric constant and 32 kV/mm of withstand voltage. The yield of anions was measured according to an electrode pattering, discharge gap between electrode, and thickness of electrode protective layer in the cluster of thick film type. We have manufactured the ceramic clusters with optimized thick film structure that have an anion over a hundred particles and the ozone of 0.6 ppb generated.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.16 no.5
• /
• pp.227-234
• /
• 2006

Microstructures of free surface and interior of glass-ceramics obtained by heat treating silicate glass specimen containing electric arc furnace dust(EAF dust) were observed. The crystallization temperature, $T_c$ of glassy specimen was measured around $850^{\circ}C$ from the result of different thermal analysis so heat treatment temperature to obtain glass-ceramic specimen was selected as $950^{\circ}C$ for 1 hr. Glass specimens containing 50 wt% dust were amorphous, while glass specimens containing 70 wt% dust showed spinel crystal peaks in XRD results. In case of glass-ceramic specimens, spinel crystalline phase was appeared with willemite, and willemite crystal peak intensity increased with increasing dust contents. The fractured surface of glass specimens containing 50 wt% dust was smooth like mirror surface, but that containing 70 wt% dust showed spinel crystals of 10 ${\mu}m$ size in glass matrix. In case of glass-ceramic specimens, ZnO crystal particles of $2{\sim}5{\mu}m$ size were produced in free surface and glassy phase, spinel and willemite crystal phases existed in interior. There were no crystals in glasses containing 50 wt% dust, while glass containing 70 wt% dust had 14 vol% crystals. Crystallinity of glass-ceramic specimens containing 50 and 70 wt% dust were 19 and 43%, respectively. When microstructures of glass and glass-ceramic specimens were observed through SEM after TCLP experiment, glass specimens showed flaking phenomenon while glass-ceramic specimens showed a slight corrosion evidence without any cracks.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.230-231
• /
• 2009

펄스 레이저 층착법 (이하 PLD)은 다성분계 산화물 박막 또는 다층구조의 박막 제작에 매우 유용한 기술이다. 본 실험에서는 KrF 엑시머 레이저를 이용하여 pt on Si 기판 위에 150nm 두께의 $Bi_{1.5}ZnNb_{1.5}O_7$(이하 BZN) 박막을 다양한 기판온도에서 제작하였다. XRD를 이용하여 BZN 박막의 구조적 특성을 분석하였고, 박막을 MIM 구조로 제작하여 유정적 특성을 측정하였다. 제조한 BZN 박막은 $500^{\circ}C$ 이상에서 결정질을, $500^{\circ}C$ 이하의 온도에서는 비정질 특성을 보였다. 유전 특성은 100 - 400$^{\circ}C$ 영역에서는 온도가 증가함에 따라 졸은 특성을 나타내었고, $500^{\circ}C$에서부터는 감소하였다. 증착 온도 $400^{\circ}C$에서 제작한 BZN 박막이 유전상수가 67.8, 유전 손실이 0.006으로 가장 줄은 유전특성을 나타내었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.3
• /
• pp.232-235
• /
• 2008

In this study, in order to develop the composition ceramics for multilayer piezoelectric actuator, PMN-PNN-PZT ceramics were fabricated using $Li_2CO_3$, $Na_2CO_3$, ZnO as sintering aids and their piezoelectric and dielectric properties were investigated according to the Bi substitution, Bi substitution induced grain growth and increase of sinterablity, And also, Bi substitution suppress secondary phase due to the liquid phase sintering effect. Bi substitution enhanced electromechanical coupling factor ($k_p$) and dielectric constant ($\varepsilon_r$), However, mechanical quality factor($Q_m$) was deteriorated, At the sintering temperature of 870 $^{\circ}C$ and Bi substitution of 1 mol%, density, electromechanical coupling factor ($k_p$), mechanical quality factor ($Q_m$), Dielectric constant ($\varepsilon_r$) and piezoelectric constant ($d_{33}$) of specimen showed the optimum values of 7,878 $g/cm^3$, 0,608, 835, 1603 and 397 pC/N, respectively for multilayer piezoelectric actuator application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.277-278
• /
• 2007

In this study, in order to develop multilayer piezo-actuator, PMN-PNN-PZT ceramics were fabricated using $Li_2CO_3,\;Na_2CO_3$, ZnO as sintering aids and their piezoelectric and dielectric properties were investigated according to the Bi substitution. Bi substitution enhanced electromechanical coupling factor$(k_p)$ and dielectric constant$({\varepsilon}_r)$. However, mechanical quality factor was deteriorated. At the sintering temperature of $870^{\circ}C$ and Bi substitution of 1mol%, density, electromechanical coupling factor$(k_p)$, mechanical quality factor$(Q_m)$, Dielectric constant$({\varepsilon}_r)$ and piezoelectric constant$(d_{33})$ of specimen showed the optimum value of $7.878g/cm^3$, 0.608, 835, 1603 and 397pC/N, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.307-307
• /
• 2007

압전액츄에이터 및 초음파진동자는 전자제품의 소형화 및 경량화, 의료기기, 모바일기기 및 소형로붓의 발전에 힘입어 그 활용범위가 넓게 확장되고 있다. 1960년 Smolenski등에 의해 $A(B_1,B_2)O_3$형 복합 페로브스카이트 구조를 갖는 강유전성 세라믹스에 대한 연구가 시작된 이래 $Pb(Co,Nb)O_3-Pb(Zr,Ti)O_3$, $Pb(Zn,Nb)O_3-Pb(Zr,Ti)O_3$, $Pb(Mg,Nb)O_3-Pb(Zr,Ti)O_3$ 등 3성분계 세라믹스의 유전, 압전 및 강유전 특성에 대한 많은 연구가 진행되어 왔다. 그러나 압전성이 우수한 세라믹스들은 Pb가 포함되어 있기 때문에 $1000^{\circ}C$ 이상에서 PbO가 급격하게 휘발되는 성질에 따라서 조성의 변동이 생겨 재현성이 어려우며 이를 방지하기 위하여 과잉 PbO를 첨가시키기 때문에 환경오염뿐만 아니라, 경제적인 측면에서도 많은 문제점을 가지고 있다. 소결조제를 이용한 산화물 첨가법은 PbO의 휘발을 억제하는 저온소결 방법중 가장 효과적인 방법으로 알려져 있다. 따라서, 본 연구에서는 적층형 압전액츄에이터로 사용하기위한 저온소결 압전세라믹스를 개발하기 위하여 PZN-PZT세라믹스에 $Li_2CO_3$, $Bi_2O_3$, CuO 를 소결조제로 사용하여 $Li_2CO_3$의 첨가량 변화에 따른 압전 및 유전 특성을 관찰하였다.