• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.134-134
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• 2016

The effect of different thermal treatments on the sub-50 nm copper nanoparticles is examined in the aspects of chemical, electrical and surface morphology. The copper nanoparticles are chemically synthesized and fabricated for paste-type solution. Simple bar coating method is practiced as a deposition process to form copper thin film on a typical slide glass. Deposited copper thin films are annealed by two different routes: general tube furnace with 99.99 % Ar atmosphere and selective laser sintering process. The thermal behavior of the different thermal-treated copper thin films is compared by SEM, XRD, FT-IR and XPS analysis. In this study, the laser sintering process ensures low annealing temperature, fast working speed and ambient-accessible route. Moreover, the laser-sintered copper thin film shows good electrical property and enhanced chemical stability than conventional thermal annealing process. Consequently, the proposed laser sintering process can be compatible with plastic substrate for flexible applications.

• Journal of the Korean Ceramic Society
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• v.29 no.6
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• pp.419-430
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• 1992

Fabrication possibility of low-shrinkage alumina without oxidation and wetting agent was presented on the basis of observation about oxidation behavior, microstructure and physical characteristics of such reaction agents free Al2O3-Al system. The composition less than Al 10w/o where Al can act as a sintering agent for Al2O3 was excluded. Under the condition of present experiments oxidation of Al2O3-Al system was dependent not on holding time but mainly on oxidation temperature. In thes case of Al powder not comminuted effectively during powder mixing of Al2O3-Al, columnar structure which would act as a hindrance to the densification during sintering developed more during oxidation with higher Al contents, and which made the fabrication of low-shrinkage Al2O3 ceramics impossible. If Al powder was comminuted effectively due to co-mixed Al2O3 characteristics, densification was improved because of no columnar structure and made the fabrication of sintered body with -2.7% dimensional change and 81% relative density possible. As a result, it is possible to fabricate dense low-shrinkage Al2O3 ceramics without oxidation and wetting agent under conditions such as smaller particle size of Al, Al contents below 50v/o, higher green density of Al2O3-Al compact and the use of Al2O3 powder used for high-density ceramics.

• Journal of Powder Materials
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• v.16 no.6
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• pp.442-448
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• 2009

$ZrB_2$-based composites are candidate materials for ultra-high temperature materials (UHTMs). $ZrB_2$ has become an indispensable ingredient in UHTMs, due to its high melting temperature, relatively low density, and excellent resistance to thermal shock or oxidation. $ZrB_2$ powders are usually synthesized by solid state reactions such as carbothermal, borothermal, or combined carbothermal reaction. SiC is added to this system in order to enhance the oxidation resistance of $ZrB_2$. In this study, $ZrB_2$?based composites were successfully synthesized and densified through two different processing paths. $ZrB_2$ or $ZrB_2$ 25 vol.%SiC was fully synthesized from oxide starting materials with reducing agents after heat treatment at 1400$^{\circ}C$. Besides, $ZrB_2$?20 vol.%SiC was fully densified with $B_4C$ as a sintering additive after hot pressing at 1900$^{\circ}C$. The synthesis mechanism and the effect of sintering additives on densification of $ZrB_2$ ?SiC composites were also discussed.

• Journal of the Korean Ceramic Society
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• v.43 no.2 s.285
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• pp.92-97
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• 2006

Dolomite type $BaSn(BO_3)_2$ ceramics with rhombohedral crystal structure has been synthesized via solid state reaction route. Dielectric properties were measured for the samples sintered at $1050\~1200^{\circ}C$ for 2 h in air. Dielectric constant, loss tangent, and temperature coefficient were increased with sintering temperature due to the evolution of $BaSnO_3$, secondary, phase. Optimum dielectric properties were obtained at the $BaSn(BO_3)_2$ ceramics sintered at $1100^{\circ}C.\;CuO/Bi_2O_3$ was added to $BaSn(BO_3)_2$ ceramics to lower the sintering temperature for LTCC application, then Co and Fe-based coloring agents were added for colorizing the LTCC tape. Typical dielectric properties of $BaSn(BO_3)_2$ ceramics with $5 wt\%\;CuO/Bi_2O_3\;and\;3wt\%$ Co-coloring agent that sintered at $900^{\circ}C$ were $\varepsilon_r=9.89,\;tan{\delta}=0.92\times10^{-3},\;and\;TCC=112ppm/^{\circ}C$. Thus obtained LTCC tape was co-fired with Ag paste for compatibility test and revealed no sign of Ag reaction with the ceramics.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.4
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• pp.47-53
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• 2002

In this study, two different (NiCuZn)-ferrite which were fabricated by using ultra-fine powders synthesized by the wet processing and conventionally commercialized powder, were investigated and compared each other in terms of the low temperature sintering and electromagnetic properties. Composition of x and w in $(Ni_{0.4-x}Cu_xZn_{0.6})_{1+w}(Fe_2O_4)_{1-w}$ were controlled as 0.2 and 0.03, respectively. The sintering temperature were $900^{\circ}C$ for ultra-fine powders by way of initial heat treatment and $1150^{\circ}C$ for commercialized powders. The (NiCuZn)-ferrite by ultra-fine powders showed love. sintering temperature than that of commercialized powders by over $200^{\circ}C$, and excellent electromagnetic properties such as the quality factor which is a important factor in the multi-layered chip inductor. In addition, characteristics of B-H hysteresis, crystallinity, microstructure and powder morphology were analyzed by a vibrating sample method(VSM), x-ray diffractometer(XRD), transmission electron microscope (TEM) and scanning electron microscope(SEM).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.11
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• pp.975-978
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• 2003

The microwave dielectric properties and the microstructures on B $i_{0.97}$T $m_{0.03}$Nb $O_4$ doped with $V_2$ $O_{5}$ were systematically investigated. B $i_{0.97}$T $m_{0.03}$Nb $O_4$ ceramics sintered at 920-96$0^{\circ}C$ were mainly consisted of orthorhombic and triclinic phases after addition of $V_2$ $O_{5}$. The apparent density increased slightly with increasing the $V_2$ $O_{5}$ addition. The dielectric constants($\varepsilon$$_{r}$) also increased with $V_2$ $O_{5}$ addition(30-45). The Q${\times}$ $f_{0}$ values measured on B $i_{0.97}$T $m_{0.03}$Nb $O_4$ ceramics doped with $V_2$ $O_{5}$ were between 2,000 and 12,000[GHz] when the sintering temperatures were in the range of 920-960[$^{\circ}C$]. It was confirmed that the temperature coefficient of the resonant frequency($\tau$$_{f}$) can be adjusted from a positive value of +10ppm/$^{\circ}C$ to a negative value of -15ppm/$^{\circ}C$ by increasing the amount of $V_2$ $O_{5}$ Based on our experimental results, the B $i_{0.97}$T $m_{0.03}$Nb $O_4$(added $V_2$ $O_{5}$) ceramics can be applied to multilayer microwave devices at low sintering temperatures.ng temperatures.emperatures.ratures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.350-353
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• 2002

The microwave dielectric properties and the microstructures on $Bi_{0.97}Nb_{0.03}O_{4}$doped with $V_{2}O_{5}$ were systematically investigated. $Bi_{0.97}Tm_{0.03}Nb_{0.03}O_{4}$ ceramics sintered at $920-960^{\circ}C$were mainly consisted of orthorhombic and triclinic phases after addition of $V_{2}O_{5}$. The apparent density increased slightly with increasing the $V_{2}O_{5}$ addition. The dielectric $constants(\varepsilon_r)$ also increased with $V_{2}O_{5}$ addition(30-45). The $Q{\times}f_0$ values measured on $Bi_{0.97}Tm_{0.03}NbO_4$ ceramics doped with $V_{2}O_{5}$ were between 2,000 and 12,000[GHz] when the sintering temperatures are in the range of $920-960[^{\circ}C]$. It was confirmed the temperature coefficient of the resonant $frequency(\tau_f)$ can be adjusted from a positive value of $+10[ppm/^{\circ}C]$ to a negative value of $-15ppm/^{\circ}C$ by increasing the amount of $V_{2}O_{5}$. Based on our experimental results, the Bi0.97Tm0.03NbO4(added V2O5) ceramics can be applied to multilayer microwave devices at low sintering temperatures.

• Journal of the Korean Ceramic Society
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• v.36 no.12
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• pp.1350-1355
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• 1999

Sintering characteristics and dielectric properties of low temperature sinterable Glass/Ceramic dielectric materials were investigated. The dielectric materials which were developed for microwave frequency applications consist of SiO2-TiO2-Bi2O3-RO system(RO:BaO-CaO-SrO) crystallizable glass and Al2O3 as a ceramic filler. Sintering experiments showed that no more densification occurred above 80$0^{\circ}C$ and bulk density and shrinkage depended on Al2O3 content only. Results of dielectric measurements showed that $\varepsilon$r Q$\times$f and $\tau$f of the material containing 30wt% Al2O3 were 17.3, 600 and +23 ppm respectively. Those values for 45 and 60wt% Al2O3 samples were 11.6, 1400, +0.7 ppm and 7.2, 2000, -8.5 ppm, repectively. The results clearly showed that the Glas/Ceramic materials of present experiment decreased in $\varepsilon$r and increased in $\times$f value and changed from positive to negative value in $\tau$f value with the increasement of Al2O3 content.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.284-284
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• 2007

In this study, the microwave dielectric property variations of (1-x)$BiNbO_4-(x)ZnNb_2O_6$ composites (x=0.3, 0.5 and 0.7) with 10wt% zinc borosilicate(ZBS) glass was investigated as a function of the substitution of $ZnNb_2O_6$ with a view to applying thes system to LTCC technology. The all composition addition of 10wt% ZBS glass ensured a successful sintering below $900^{\circ}C$. In addition, a small amount of $Bi_2SiO_5$ as the secondary phase was observed in the all composition. The substitution of $ZnNb_2O_6$ on the $BiNbO_4$ composites increased the $Q{\times}f$ values, but it decreased the sinterability and dielectric constant due to the high sintering temperature and low dielectric constant of $ZnNb_2O_6\;than\;BiNbO_4$ ceramics. The increasing of $ZnNb_2O_6$ content from 0.3 to 0.7 in the (1-x)$BiNbO_4-(x)ZnNb_2O_6$ composites with 10wt% ZBS glass sintered at $900^{\circ}C$ demonstrated 28.1~15.6 in the dielectric constant$({\varepsilon}_r)$, 5,500~8,700GHz in the $Q{\times}f$ value.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.279-279
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• 2007

Synthesis and dielectric properties of glass-ceramic composites with zinc borosilicate glass(here after ZBS glass) were investigated as functions of $ZnAl_2O_4$ phase synthesis method, glass addition (50~60 vol%) and sintering temperature ($600{\sim}950^{\circ}C$ for 2 hrs). The 50 vol% ZBS glass-$Al_2O_3$ and 60 vol% ZBS glass-$ZnAl_2O_4$ ensured successful sintering below $900^{\circ}C$. But the composition of 100-x-y vol% ZBS glass-x vol% $Al_2O_3-y$ vol% ZnO exhibited poor sinterability below $900^{\circ}C$ and the swelling phenomenon occurred in this composite with the large amount of ZBS glass. The sintering behavior of Glass-ceramic composites was affected by the crystallization of $ZnAl_2O_4$ which was formed by the reaction between ZBS glass and $Al_2O_3$. Dielectric constant (${\varepsilon}_r$), $Q{\times}f$ value and temperature coefficient of resonant frequency (${\tau}_f$) of the composite with 50 and 60 vol% ZBS glass contents demonstrated $ZBS-Al_2O_3({\varepsilon}_r=5.7)$, $ZBS-ZnAl_2O_4({\varepsilon}_r=5.8)$ which is applicable to substrate requiring an low dielectric properties.