• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.2
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• pp.144-150
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• 2008

Recently, there has been growing interest in low loss and low dielectric constant material for LTCC application, as the frequency range for electronic devices increases. This study was designed to evaluate the effect of cordierite filler for low dielectric constant LTCC material. From the previous experiments, two glass compositions of B-Si-Al-Zn-Ba-Ca-O and B-Si-Al-Sr-Ca-O system, were chosen. Each powder of two glass compositions was sintered respectively with commercial cordierite powder in temperature range from $800^{\circ}C\;to\;900^{\circ}C$. Crystalline cordierite and glass peaks were affected only with two factors of composition and sintering temperature among various factors. With the optimized condition of two cordierite/glass compositions, obtained dielectric constant was below 5.5 and quality factor was above 1,000. Closed pore of sintered body was controled by sintering temperature and sintering time. When cordierite/glass composite with ratio of 5.5:4.5 was sintered at $900^{\circ}C$, densification was sufficient with good dielectric characteristics of ${\epsilon}_r<5.1,\;Q{\ge}1,000$. Residual fine closed pores could be reduced with control of sintering temperature and time. 3 point bending strength and chemical durability were evaluated to obtain feasibility for substrate material.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.12
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• pp.1039-1043
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• 2007

In this paper, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator application, PMN-PZN-PZT ceramics were fabricated using $LiCO_3,\;Bi_2O_3$ and CuO as sintering aids. And also, their piezoelectric and dielectric properties were investigated according to the milling time. All the specimens sintered at $930\;^{\circ}C$ showed tetragonal phases without secondary phases. With increasing milling time, piezoelectric and dielectric characteristic of specimens increased up to 60 hours milling time and then decreased due to the agglomeration of fine particle. Accordingly, it seems that 60 hour is optimum milling condition. At the sintering temperature of $930\;^{\circ}C$ and milling time of 60 hour, density, dielectric constant(${\varepsilon}_r$), electromechanical coupling factor (kp), mechanical quality factor (Qm), piezoelectric d constant showed the optimum value of $7.95\;g/m^3$, 1382, 0.546, 1749, 330 pC/N, respectively for multilayer piezoelectric actuator application.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.641-647
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• 2011

The present study aims to identify the effect of sintering atmosphere [$O_2$, 75$N_2$-25 $H_2$ (mol%) and $H_2$] on microstructural evolution at the relatively low sintering temperature of 1040$^{\circ}C$. Samples sintered in $O_2$ showed a bimodal microstructure consisting of fine matrix grains and large abnormal grains. Sintering in 75 $N_2$ - 25 $H_2$ (mol %) and $H_2$ caused the extent of abnormal grain growth to increase. These changes in grain growth behaviour are explained by the effect of the change in step free energy with sintering atmosphere on the critical driving force necessary for rapid grain growth. The results show the possibility of fabricating $(K_{0.5}Na_{0.5})NbO_3$ at low temperature with various microstructures via proper control of sintering atmosphere.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.214-215
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• 2005

In this paper, in order to develop low temperature sintering piezoelectric ceramics for piezoelectric transformer, PMW-PMN-PZT ceramics using 0.25wt%$CaCO_3$ and 0.2wt%$Li_2CO_3$ as sintering aids were fabricated according to the variation of amount of PMW and Zr/Ti ratio. Specimens could be sintered at 900$^{\circ}C$ by adding sintering aids. As Zr/Ti ratio was increased, kp was increased and Qm was decreased by approaching MPB region, and kp showed the largest value of 0.58 at Zr/Ti:50/50. The variation of amount of PMN substitution affected the liquid phase sintering of the ceramics using sintering aids, and decreased piezoelectric properties.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.1
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• pp.1-8
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• 2024

Phase stability of tetragonal crystals in yttria-stabilized zirconia ceramics is dependent on the content of yttria and the heat-treatment condition, related with mechanical properties. In this study, we fabricated the 1.5 mol% yttria-stabilized zirconia (1.5Y-YSZ) ceramics by cold isostatic pressing (CIP) and post-sintering at temperature range of 1200 to 1350℃ for 2 hours and investigated the sintered properties and microstructural evolution. Sintered and microstructural parameters, i.e, apparent density, grain size and phase composition of 1.5Y-YSZ ceramics were mainly dependent on the sintering temperature. Maximum sintered density of 99.4 % and average grain size of 200-300 nm could be obtained from the heat-treatment condition above sintering temperature at 1300℃ for 2 hours, possessing the superior mechanical hardness with 1200 Hv. However, phase stability of tetragonal grains in 1.5 YSZ ceramics is very low, inducing the phase transformation to monoclinic crystals on specimen surface during cooling after heat-treatment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.454-457
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• 2010

The influence of CuO addition on what of the $(Ba,Sr)TiO_3$ ceramics was studied. The sintering temperature of $(Ba,Sr)TiO_3$ ceramics was lowered by the addition of CuO additives. The 1 - 5 wt% CuO were selected and employed as the sintering aids. Low-Temperature Co-fired Ceramic technologies are popular technologies used in the manufacture of microwave devices. In this study, crystalline and electrical properties of CuO doped $(Ba,Sr)TiO_3$ ceramics were investigated to determine the low temperature sintering properties. The addition of CuO to $(Ba,Sr)TiO_3$ lowered the sintering temperature from $1350^{\circ}C$ to $1150^{\circ}C$. The dependence of the sintering temperature shrinkage rate and mechanism of CuO doped $(Ba,Sr)TiO_3$ ceramics are investigated and discussed. Also, the crystalline structure of CuO - doped $(Ba,Sr)TiO_3$ ceramics is discussed by the X-ray diffraction (XRD) method.

• Journal of the Korean Ceramic Society
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• v.27 no.3
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• pp.337-344
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• 1990

As a function of sintering temperature and time, the electrical properties of ruthenium based thick film resistors were investigated with microstructure. The variatio of resistivity and TCR(temperature coefficient of resistance)trends of sintered speciman at various sintering temperature were different low resistivity paste(Du Pont 1721) from high one(Du Pont 1741). These phenomena are deeply relative to microstructure of sintered film. With increasing the sintering temperature for 1721 system, the electrical sheet resistivity decreased, but again gradually increased above 80$0^{\circ}C$. And TCR trends in 1721 system are all positive. On the other hand the electrical sheet resistivity of 1741 resistor system decreased with sintering temperature. And TCR trends variable according to sintering temperature. TCR of speciman sintered at $700^{\circ}C$ was negative value, and TCR of 80$0^{\circ}C$ sintered speciman coexisted negative and positive value. But in case of speciman sintered at 90$0^{\circ}C$, TCR was positive value. As results of this fact, it was well known that the charge carrier contributied to electrical conduction in 1741 resistor system varied with sintering temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.178-180
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• 2005

In this study, in order to develop multilayer low temperature sintering piezoelectric transformer, $Pb_{0.97}Sr_{0.03}[(Mn_{1/3}Nb_{2/3})x(Zr_{0.48}Ti_{0.52})_{1-x}O_3]+$ 0.25wt% $CeO_2$+0.3 wt% $Nb_2O_5$ system ceramics were fabricated using $Li_2CO_3-CaCO_3$ and CuO as sintering aids and their piezoelectric and dielectric characteristics were investigated with the amount of PMN substitution. With increasing PMN substitution, electromechanical coupling factor kp and dielectric constant were increased.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.638-644
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• 2000

The sintering behaviors of the glass-alumina composites for low firing temperature were investigated as functiions of the volume fraction of alumina powder and the particle size with respect to porosity and pore shape. As the volume fraction of alumina powder was increased or the particle size of it was decreased, the sintering temperature of open pore-closing was raised. When the volume fractions of alumina which had 2.19$\mu\textrm{m}$ median diameter were increased with 20, 30, 40, and 50%, the sintering temperatures of open pore-closing were 425, 450, 475, and 500$^{\circ}C$. And when the median particle size of alumina was diminished from 2.19$\mu\textrm{m}$ to 0.38$\mu\textrm{m}$, the sintering temperature of open pore-closing was increased from 450$^{\circ}C$ to 475$^{\circ}C$. Especially, the sintering temperature, which showed maximum density, was corresponded with the stage of open pore-closing and after achieving maximum density over heating resulted in dedensification of specimen, so called, over-firing behavior.

• Ceramist
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• v.23 no.2
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• pp.114-131
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• 2020

Fracture in the titanium carbonitride-metal composites occurs by crack propagation through the carbonitride grains or in the interfaces. Thus, intrinsic properties of the carbonitride need to be enhanced and the interfaces should be also modified to coherent structure to strengthen the composites. Especially, interfacial structure can be the main factor to determine the mechanical properties of titanium carbonitride-metal composites because the interfaces between carbonitride grains and metallic phase are weak parts due to heterogeneous nature of carbonitride and metallic phase. In this paper, methodologies for improving the interfacial structure of titanium carbonitride-metal composites are suggested. Total area of the interfaces can be reduced using solid solution type carbonitrides as raw materials instead of a mixture of various carbonitrides in the composites. Also, synthesis of titanium carbonitride-metal composite powders and the low-temperature sintering of the composite powders for short time can be the way for formation of coherent interfaces. The sintering of the composite powders for short time at low temperature can reduce the potential of formation of interfaces by dissolution and precipitation of carbonitride in the liquid metal. As a result of formation of coherent boundaries due to low-temperature and short-time sintering, interfaces between titanium carbonitride grains and metallic phase have the favorable structure for the enhanced fracture toughness. It is believed that the low-temperature sintering of solid solution type composite powders for short time can be the way to improve the low toughness of the titanium carbonitride-metal composites.