• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제27권6호
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• pp.372-376
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• 2014

We investigated the effect of excess CuO on the sintering behavior, ferroelectric, and piezoelectric properties of lead-free $Bi_{0.5}(Na_{0.82}K_{0.18})_{0.5}TiO_3$ (BNKT) ceramics. The addition of excess CuO was found to greatly contribute to the densification and grain growth, however, excess CuO over 3 mol% was precipitated at grain boundaries after sintering. BNKT with 1~2 mol% CuO in excess sintered at $975^{\circ}C$ showed piezoelectric properties comparable to those of unmodified BNKT sintered at $1,175^{\circ}C$. These results seem meaningful for its application to low cost multilayer actuators (MLAs) because low firing ceramics make it possible to apply less expensive base metals to the inner electrode of MLAs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제9권6호
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• pp.606-611
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• 1999

Low dielectric Mullite/Glass composites for substrates were fabricated by mullite by synthesized from kaolin and alumina, and borosilicate glass. By the liquid-sintering, the composites were densified at low sintering temperature in air, allowing confiring with Cu, Ag, Au and Ag-Pd. Crystallization of the borosilicate glass was not occurred. The mullite/50 wt% glass composites fired between 950 and $1100^{\circ}C$ showed good properties for high-performed substrate, such as low dielectric constant (5.2~5.4, at 1MHz), low coefficient of thermal expansion (5.3~$5.7{\times}10^{-6}{\cdot}^0C^{-1}$), and bending strength of 130 MPa.

• Journal of the Korean institute of surface engineering
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• 제48권4호
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• pp.158-162
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• 2015

To substitute indium tin oxide (ITO), many substituents have been studied such as metal nanowires, carbon based materials, 2D materials, and conducting polymers. These materials are not good enough to apply to an electrode because theses exhibit relatively high resistance. So metal grids are required as an additionalelectrode to improve the conductivities of substituents. The metal grids were printed by electrohydrodynamic printing system using Ag nanoparticle based ink. The Ag grids showed high uniformity and the line width was about $10{\mu}m$. The Ag nanoparticles are surrounded by dispersants such as unimolecular and polymer to prevent aggregation between Ag nanoparticles. The dispersants lead to low conductivity of Ag grids. Thus, the sintering process of Ag nanoparticles is strongly recommended to remove dispersants and connect each nanoparticles. For sintering process, the interface and microstructure of the Ag grid were controlled in 1.0 torr Ar atmosphere at aound $400^{\circ}C$ of temperature. From the sintering process, the uniformity of the Ag grid was improved and the defects on the Ag grids were reduced. As a result, the resistivity of Ag grid was greatly reduced up to $5.03({\pm}0.10){\times}10^{-6}{\Omega}{\cdot}cm$. The metal grids embedded substrates containing low pressure Ar sintered Ag grids showed 90.4% of transmittance in visible range with $0.43{\Omega}/{\square}$ of sheet resistance.

• Journal of the Korean Ceramic Society
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• 제30권5호
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• pp.381-388
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• 1993

Due to the anisotropy of thermal expansion, LAS system which has low thermal expansion property is hard to obtain a dense sintered body. Therefore, the thermal expansion coefficient and the mechanical strength were decreased. In this study, mullite, which has good mechanical properties in high temperature and comparatively low thmeral expansion coefficient, was taken as a additive in LAS system. And then, sintering, thermal, and mechanical properties were investigated. The results are follows; When mullite is added in eucryptite composition (Li2O.Al2O3.2SiO2) of LAS system, the creation of liquid phase results in the densification of sintered body and the specimen sintered at 136$0^{\circ}C$ for 2 hours shows optimum sintering condition. With the addition of mullite in eucryptite composition, mechanical strength is increased by the control of grain growth. Especially, flexual strength of EM0 specimen was about double value than the basic composition. Thermal expansion coefficients of EM0 and EM15 specimens sintered at 136$0^{\circ}C$ were -8.23$\times$10-6/$^{\circ}C$ and -4.90$\times$10-6/$^{\circ}C$ in the temperature range of RT.~80$0^{\circ}C$. As the mullite content are increased, negative thermal expansion ratios are decreased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.646-649
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• 2002

The microwave dielectric properties and the structure of $Sb_2O_5$ modified $BiNb_xSb_{1-x}O_4$ ceramics were investigated. The structure of these ceramics were orthohombic phase at all sintering temperatures and there were not the second phase. These ceramics added sintering additive such as CuO and $V_2O_5$ were sinterable at a low temperature$(880^{\circ}C{\sim}960^{\circ}C)$ by liquid phase. Dielectric properties of $BiNb_xSb_{1-x}O_4$ ceramics were also improved than these of $BiNbO_4$ ceramics. The content of modified atom controlled the microstructure, dielectric constant and quality factor. As a result, We could obtain following result; ${\varepsilon}r$=42~44, $Q{\cdot}f_0$=20,000~42,000GHz, $\tau_f=-7{\sim}-28ppm/^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제28권3호
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• pp.160-164
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• 2015

In this study, $(1-x)Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3+xCeMnO_3$ (x= 0~0.02) ceramics were prepared by Columbite precursor method. The phase structure, ferroelectric and piezoelectric properties were systematically investigated. It was found that PMW-PNN-PZT possessed superior electrical properties due to its composition close to the MPB (morphotropic phase boundary). Coercive electric field of 10.05 [kV/cm] and density of 7.88 [$g/cm^3$] were obtained when the substitution amount of $CeMnO_3$ is x=0.02. In contrast, specimens with x=0.01 showed the mechanical quality factor($Q_m$) of 1,091 and the electromechanical coupling factor($k_p$) of 0.613.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 1992년도 추계학술대회 논문집
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• pp.38-41
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• 1992

Pb(Zr,Ti)$O_3$ powders were synthesized by the partial oxalate method and the modified partial oxalate method, where the difference between the two is the use of pre-reacted (Zr,Ti)$O_2$ in the former method. When compared with conventional mixed oxide method, calcination temperature can be reduced to less than $700^{\circ}C$ by both partial oxalate methods, and the resulting particle size was finer and more uniform. Using partial oxalate-derived PZT powders, sintering temperatures can also be reduced as low as $950^{\circ}C$ without sacrificing desired dielectric and piezoelectric properties, such as relative permittivity, electromechanical coupling factor, and piezoelectric coefficient. Two partial oxalate methods yield ceramics with almost the same physical and electrical properties, so that the step of producing ZTO powder does not seem to be necessary.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.236-239
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• 2003

In this study, to develop the low temperature sintering ceramics for piezoelectric transformer, PSN-PNN-PZT system ceramics were manufactured as a function of $MnO_2$ addition. Its dielectric and piezoelectric characteristics were investigated. With increasing the amount of $MnO_2$ addition, electromechanical coupling factor(kp) were increased until 0.3wt% $MnO_2$ and that after decreased. mechanical quality factor(Qm) showed the maxinum value at 0.5wt% $MnO_2$. For piezoelectric transformer application, the 0.5wt% $MnO_2$ added specimen sintered at $1,000^{\circ}C$ showed the proper value of ${\varepsilon}r$= 1,646, kp=0.55 and Qm=439.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제14권9호
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• pp.4185-4190
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• 2013

We executed the property changes of the sintered MgO (99.9% purity, 300nm size) specimens with addition to CaO content of 0.00wt%, 0.25wt%, and 0.50wt%, processed at 7GPa, for 5min, 600~$800^{\circ}C$. To investigate the micro-structure and physical property changes of the sintered MgO(-CaO), we employed a scanning electron microscopy(SEM), X-ray diffractomerty(XRD), Vickers hardness, and density. The SEM result showed that MgO powder of 300nm size was changed into sintered structure of 520nm by high pressure and low temperature sintering, regardless of the CaO contents. According to the XRD analysis, no CaO phase observed, while MgO peaks shift indicated the existence of CaO in the MgO matrix. The Vickers hardness result showed that hardness of sintered MgO-CaO increased by 12% compared pure MgO under the same temperature conditions. It implied that we can obtain the same hardness with $100^{\circ}C$ lowered sintering temperatures by addition of CaO. The density results showed that it was possible to obtain density of 98%, which is 5% greater than that of pure MgO at low temperature of $600^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.303-304
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• 2005

Add $Li_2CO_3$ to $(Ba_{0.6}Sr_{0.4})$ $TiO_3$ powder to lower sitering temperature in this research, made thick film by tape casting method. Investigated about sitering temperature and physical properties that added $Li_2CO_3$ Even if lower sitering temperature about $200^{\circ}C$ adding $Li_2CO_3$ 10wt.%, density was near to 5.7$g/cm^3$ that is theoretical values, and crystal structure examined as perobeuseukaiteu senior after sintering.