• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.309-309
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• 2007

The LTCCs (low-temperature co-fired ceramics) are very important for electronic industry to build smaller RF modules and to fulfill the necessity for miniaturization of devices in wireless communication industry. The dielectric materials with sintering temperature $T_{sint}$<$900^{\circ}C$ are required. In this study, we investigated with glass-ceramic composition, which was crystallized with two crystals. The microstructure, crystal phases, thermal and mechanical properties, and dielectric properties of the composites were investigated using FE-SEM, XRD, TG-DTA, 4-point bending strength test and LCR measurement. The starting temperature for densification of a sintered body was at $779{\sim}844^{\circ}C$ and the glass frits were formatted to the crystal phases, $CaAl_2Si_2O_8$(anorthite) and $CaMgSi_O_6$(diopside), at sintering temperature. The sintered bodies exhibited applicable dielectric properties, namely 6-9 for ${\varepsilon}_r$. The results suggest that the glass-ceramic composite would be potentially possible to application of low dielectric L TCC materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.31-34
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• 2007

In this study, in order to develop multilayer ceramics vibrator for ultrasonic nozzle, PMN-PNN-PZT ceramics were fabricated using $Li_{2}CO_{3}-Na_{2}_CO_{3}$ as sintering aids and their piezoelectric and dielectric characteristics were investigated according to the amount of PbO. With increasing PbO contents, secondary phases were increased and phase structure was changed from tetragonal structure to rhombohedral structure and also electromechanical coupling factor was linearly decreased. At the composition ceramics with the sintering temperature of $870^{\circ}C$ and 1 mol% excess PbO, density, electromechanical coupling factor, dielectric constant, piezoelectric d constant and mechanical quality factor showed the optimum value of $7.879\;g/cm^{3}$, 0.55, 1149, 328 pC/N, 1224, respectively for multilayer ceramics vibrator application for ultrasonic nozzle.

• Journal of the Korean Ceramic Society
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• v.34 no.11
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• pp.1187-1197
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• 1997

Dry gel composed of primary particles more homogeneous than starting boehmite powder was prepared by dispersing and gelling the boehmite powder. The transformation temperatures of boehmite powder, dry gel seeded with 0, 1, 3, 5 wt% $\alpha$-Al2O3, and ball milled gel were 1192$^{\circ}C$, 1184$^{\circ}C$, 1141$^{\circ}C$, 1119$^{\circ}C$, 1117$^{\circ}C$, and 1106$^{\circ}C$, respectively. Sintering behavior of dry gel without seed was similar to that of boehmite powder, but the sintered density of dry gel was improved as much as 10%~15% than boehmite powder. In the case of dry gel seeded with 5 wt% $\alpha$-Al2O3, sintering behavior was much improved. The relative density of the gel seeded with 5 wt% $\alpha$-Al2O3 was 96% when sintered at 140$0^{\circ}C$ for 1h. On the other hand, ball milling of the non-seeded sol for 48h resulted in the relative density of 97% when sintered at 130$0^{\circ}C$ for 1h. The size and amount of $\alpha$-Al2O3 particles added by ball milling were 0.107 ${\mu}{\textrm}{m}$ and 0.5 wt%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.435-438
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• 2004

The effects sintering additives such as $xwt%(0.242Bi_2O_3-0.782V_2O_5)$ on the microwave dielectric and sintering properties of $MgCo_2(VO_4)_2$ ceramics were investigated. Highly dense samples were obtained for $MgCo_2(VO_4)_2$ at the sintering temperature of $950^{\circ}C$ with $0.242Bi_2O_3-0.758V_2O_5$ additions of $0.5{\sim}5wt%$. The microwave dielectric properties of $MgCo_2(VO_4)_2$ with $0.5wt%(0.242Bi_2O_3-0.758V_2O_5)$ sintered at $950^{\circ}C$ were as follows : $Q{\times}f_0\;=\;45,375GHz,\;\epsilon_r\;=\;9.7\;and\;\tau_f\;=\;-23.2ppm/^{\circ}C$.

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

• Transactions on Electrical and Electronic Materials
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• v.9 no.3
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• pp.91-95
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• 2008

In this study, in order to develop the composition ceramics for low loss multilayer piezoelectric actuator application, $Pb(Zn_{1/2}W_{1/2})O_3-Pb(Mn_{1/3}Nb_{2/3})O_3-Pb(Zr,Ti)O_3$ (abbreviated as PZW-PMN-PZT)ceramics according to the amount of $MnO_2$ addition were fabricated using two-stage calcinations method. And also, their dielectric and piezoelectric properties were investigated. At the 0.2 wt% $MnO_2$ added PZW-PMN-PZT ceramics sintered at $930^{\circ}C$, density, electromechanical coupling factor $k_p$, dielectric constant ${\varepsilon}_r$, piezoelectric $d_{33}$ constant and mechanical quality factor $Q_m$ showed the optimum value of $7.84g/cm^3$, 0.543, 1,392, 318.7 pC/N, 1,536, respectively for low loss multilayer ceramics actuator application.

• Journal of the Korean Ceramic Society
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• v.19 no.2
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• pp.152-156
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• 1982

The behavior of magnesite during hot pressing is studied from 80$0^{\circ}C$ to 110$0^{\circ}C$ by Knoop hardness test, X-ray diffraction and electron microscopy. The growth of magnesia crystallite in magnesite is observed at 110$0^{\circ}C$ and crystallite size is about 2 microns. It is also observed that hot pressing showes enhanced sinterability comparing to ordinary pressure-less sintering. The magnesia body with 95 per cent of theoretical density is obtained by hot pressing at relatively low temperature such as 110$0^{\circ}C$.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.121-125
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• 2002

이동통신기기 등의 고주파용 LTCC(Low Temperature Co-fired Ceramic) LC filter의 소결결에 있어 기존의 소결공정인 전기로 소결공정과 microwave를 이용한 소결공정을 이용하여 소결하였을때 LC filter의 수축율과 무게감소, 그에 따른 밀도의 변화, SEM을 이용한 표면형상 분석을 통해 급속가열을 통한 공정시간의 단축, 낮은 에너지 소비로 인한 제조단가의 절감, 균일한 가열로 인한 소결온도의 저하 등의 장점을 갖는 microwave sintering을 적용할 수 있는 가능성을 제시하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.4
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• pp.150-155
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• 2020

Alumina (Al₂O₃) is mainly used as a structural ceramic material and to have good mechanical properties requires a dense microstructure. In commercial fabrication, the liquid phase sintering process is adjusted to reduce the sintering temperature of alumina. In this study, the effect of added amounts of cobalt oxide as a coloring agent on the microstructure and mechanical properties was investigated in the CaO-SiO₂-MgO-system liquid phase sintering of 92 % alumina at various sintering temperatures. When 11 wt% Co₂O₃ was added, a rearrangement of alumina particles, which is the main densification step in liquid phase sintering, occurred from a sintering temperature of 1200℃. Solution re-precipitation and coalescence steps followed from 1300℃ with the grain growth of alumina particles. The addition of excess Co₂O₃ and sintering temperatures above 1400℃ resulted in a decrease in sintered density and Vickers hardness, because of the low viscosity of the liquid phase. In 92 % alumina with the addition of 11 wt% Co₂O₃, a sintered density and Vickers hardness of 3.86 g/㎤ and 12.32 GPa, respectively, were obtained at a sintering temperature of 1350℃.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1162-1168
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• 1995

Systematic studies of the effects of additives and processing variables on the sintered density and the effect of crystalline forms of starting powders on the microstructure of pressureless sintered silicon carbide are described. Oxide additives were effective for the densification of SiC up to 96% of theoretical density at temperature as low as 185$0^{\circ}C$. Use of embedding powder increased the sintered density, up to 98% of theoretical density, by decreasing the weight loss during sintering. Composite type duplex microstructure has been developed due to the $\beta$longrightarrow$\alpha$ phase transformation of SiC by sintering at 185$0^{\circ}C$ and heat treatment at 195$0^{\circ}C$ for 1h.