• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.386-389
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• 2001

In this study, development of a new LTCC material using non-glassy system was attempted with repsect to reducing the fabrication process steps and cost down. Lowering the sintering temperature can be achieved by liquid phase sintering. However, presence of liquid phases usually decrease dielectric properties, especially the quality factor. Therefore, the starting material must have quality factor as high as possible in microwave frequency range. And also, the material should have a low dielectric constant for enhancing the signal propagation speed. Regarding these factors, dielectric constants of various materials were estimated by the Clausius-Mosotti equation. Among them, $ZnWO_4$ was turned out the suitable LTCC material. $ZnWO_4$ can be sintered up to 98% of full density at $1050^{\circ}C$ for 3 hours. It's measured dielectric constant, quality factor, and temperature coefficient of resonant frequency were 15.5, 74380GHz, and $-70ppm/^{\circ}C$, respectively. In order to modify the dielectric properties and densification temperature, $B_{2}O_{3}$ and $V_{2}O_{5}$ were added to $ZnWO_4$. 40 mol% $B_{2}O_{3}$ addition reduced the dielectric constant from 15.5 to 12. And the temperature coefficient of resonant frequency was improved from -70 to $-7.6ppm/^{\circ}C$. However, sintering temperature did not change due to either lack of liquid phase or high viscosity of liquid phase. Incorporation of small amount of $V_{2}O_{5}$ in $ZnWO_{4}-B_{2}O_{3}$ system enhanced liquid phase sintering. 0.1 wt% $V_{2}O_{5}$ addition to the $0.6ZnWO_{4}-0.4B_{2}O_{3}$ system, reduced the sintering temperature down to $950^{\circ}C$. Dielectric constant, quality factor, and temperature coefficient of resonant frequency were 9.5, 16737GHz, and $-21.6ppm/^{\circ}C$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.386-389
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• 2001

In this study, development of a new LTCC material using non-glassy system was attempted with respect to reducing the fabrication process steps and cost down. Lowering the sintering temperature can be achieved by liquid phase sintering. However, presence of liquid phases usually decrease dielectric properties, especially the quality factor. Therefore, the starting material must have quality factor as high as possible in microwave frequency range. And also, the material should have a low dielectric constant for enhancing the signal propagation speed. Regarding these factors, dielectric constants of various materials were estimated by the Clausius-Mosotti equation. Among them, ZnWO$_4$ was turned out the suitable LTCC material. ZnWO$_4$ can be sintered up to 98% of full density at 105$0^{\circ}C$ for 3 hours. It's measured dielectric constant, quality factor, and temperature coefficient of resonant frequency were 15.5, 74380GHz, and -70ppm/$^{\circ}C$, respectively In order to modify the dielectric properties and densification temperature, B$_2$O$_3$ and V$_2$O$_{5}$ were added to ZnWO$_4$. 40 mol% B$_2$O$_3$ addition reduced the dielectric constant from 15.5 to 12. And the temperature coefficient of resonant frequency was improved from -70 to -7.6ppm/$^{\circ}C$. However, sintering temperature did not change due to either lack of liquid phase or high viscosity of liquid phase. Incorporation of small amount of V$_2$O$_{5}$ in ZnWO$_4$-B$_2$O$_3$ system enhanced liquid phase sintering. 0.lwt% V$_2$O$_{5}$ addition to the 0.6ZnWO$_4$-0.4B$_2$O$_3$ system, reduced the sintering temperature down to 95$0^{\circ}C$ Dielectric constant, quality factor, and temperature coefficient of resonant frequency were 9.5, 16737GHz, and -21.6ppm/$^{\circ}C$ respectively.ively.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.337-341
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• 2012

Mechanochemical processing (MCP) involves several high-energy collisions of powder particles with the milling media and results in the increased reactivity/sinterability of powder. The present paper shows results of mechanochemical processing (MCP) of silicon nitride powder mixture with the relevant sintering additives. The effects of MCP were studied by structural changes of powder particles themselves as well as by the resulting sintering/densification ability. It has been found that MCP significantly enhances reactivity and sinterability of the resultant material: silicon nitride ceramics could be pressureless sintered at $1500^{\circ}C$. Nevertheless, a degree of a silicon nitride crystal lattice and powder particle destruction (amorphization) as detected by XRD studies, is limited by the specific threshold. If that value is crossed then particle's surface damage effects are prevailing thus severe evaporation overdominates mass transport at elevated temperature. It is discussed that the cross-solid interaction between particles of various chemical composition, triggered by many different factors during mechanochemical processing, including a short-range diffusion in silicon nitride particles after collisions with other types of particles plays more important role in enhanced reactivity of tested compositions than amorphization of the crystal lattice itself. Controlled deagglomeration of $Si_3N_4$ particles during the course of high-energy milling was also considered.

• Journal of the Korean Wood Science and Technology
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• v.45 no.6
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• pp.671-681
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• 2017

Oil palm trunk (OPT) is a potential source of biomass for the production of biopellet. In the present research, biopellet were prepared from the meristem part of 25 years old OPT with various percentages of its bark (0, 10, and 30%). The highest biopellet durability was found for biopellet produced at $130^{\circ}C$ of pelletizing temperature with 30% bark content. Scanning electron microscopy (SEM) of biopellet showed the weak of particle bonding due to the low pelletizing pressure. The moisture content, unit density, ash content, and caloric value of OPT-based pellets were 3.55-5.35%, $525.56-855.23kg/m^3$, 2.76-3.44%, and 17.89-19.14 MJ/kg, respectively. The combustion profiles obtained by thermogravimetric analysis (TGA) seemed to be unaffected by the bark content on. Differential thermal analysis of TGA curve indicated different pyrolysis characteristic of hemicellulose, cellulose, and lignin.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.2
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• pp.9-13
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• 2001

The effects of glass addition on the densification and the microwave properties of $(Ba_{0.5}Pb_{0.5})Nd_2Ti_5O_{14}$ dielectric system were studied. When 2~3 wt% of borosilicate glass were added, the density increased and the better microwave properties were obtained. When a sample was sintered at $950^{\circ}C$ with 3 wt% of glass, the quality factor and the temperature coefficient of the resonant frequency of the specimen were 4500 and +10 $ppm/^{\circ}C$, respectively. The dielectric constant, however, decreased from 90 to 75 with glass addition.

• Journal of the Korean Ceramic Society
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• v.21 no.1
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• pp.33-40
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• 1984

To find out the optimum heating profile for the nitridation of compacts of graded silicon grains (max 53$mu extrm{m}$) two batches with the addition of MgO and $Mg(NO_3)_3$$cdot$$6H_2O$ to silicon particles were isostatically pressed into compacts. They were nitrided under some different nitriding schedules. The properties such as bulk densitis microstructures and formed phases were measured and observed. The following results were obtained ; 1) About 10% unreacted silicon remained in specimen which was nitrided at 1, 350$^{\circ}C$ for 240hrs. 2) One of the step-heating processes 1, 150$^{\circ}C$-1, 390$^{\circ}C$ for 65hrs are then $1, 390^{\circ}C$for 50hrs was the low temperature but with that at high temperature. 3) High pressure(10.5kgf/$cm^2$) of nitrogen at 1, 390$^{\circ}C$ accelerated the $\alpha$$ ightarrow$$\beta$ transformation of silicon nitride. 4) Magnesium nitrate was superior to magnesium oxide in the role of nitriding aid and the formation of uniform microstructures.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.816-820
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• 2005

The doped-ceria is a strong candidate material for an intermediate temperature SOFC. However, the mechanical strength and the magnitude of electrical conductivity need to be increased at low sintering temperature. In this study, to improve both properties, $1at\% $ of Mg, Ca, Cr, Fe, Co, Ni, Cu, Ga, and Zr were added to the GDC20 ($20at\%$ Gd-doped Ceria) and sintered at $1350^{\circ}C$ that is $250^{\circ}C$ lower than $1600^{\circ}C$. With addition, the relative density of the sintered sample increased. Fe, Co, Ni, Cu, Ga doped-GDC20 showed high relative density over $92\%$. Among them, Ga doped-GDC20 showed the most improved sinterability. The conductivity of doped­GDC20 increased by $\~10$ times at $300\~700^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.11
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• pp.854-858
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• 2010

In this study, we have investigated the effects of Cr dopant on the sintering and electrical properties of ZnO-$Sb_2O_3$ (ZS) ceramics for varistor application. Spinel phases including $\alpha-$ and $\beta$-type was formed at ZS system and $\alpha$-spinel was stabilized by Cr doping in ZS system. Densification of ZS and ZSCr system was retarded to $1000^{\circ}C$ by the formation of spinel at $800^{\circ}C$. The morphology and its distribution of spinel phases in ZS system was homogeneous but disturbed by Cr doping. In ZSCr the densification of ZnO compared with ZS system was more retarded by low concentration of Zn interstitial defects induced by Cr doping in addition to the effect of spinel phase formation. The defects in each system were identified as attractive coulombic center (ZS: 0.13 eV, ZSCr: 0.12 eV) and singly charged oxygen vacancy $V_0^{\cdot}$ (ZSCr: 0.33 eV). In all ZS and ZSCr system have week varistor behavior by the formation of double Schottky barrier at grain boundary but its stability of barrier was very sensitive to sintering temperature.

• Journal of the Korean Ceramic Society
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• v.46 no.2
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• pp.175-180
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• 2009

Multilayer ceramic capacitors (MLCCs) have continually been made smaller in size and larger in capacity in resent years. However, the end termination electrode is still thick in many MLCCs. In this study, we used small grain glass frit to embody thin film and highly densification in the end termination by improve sintering driving force with well-dispersion and rising surface energy. Pastes were fabricated using size changed glass frit, such as 0.1 ${\mu}m$, 0.5 ${\mu}m$, 1.0 ${\mu}m$, 4.0 ${\mu}m$. Fabricated pastes were applied 05A475KQ5 chip and fired various sintering temperatures to analyze sintering behavior of pastes. Consequently, small glass frit used pastes have many merits than larger, such as well-dispersion, improve cornercoverage and surface roughness, possibility of low temperature sintering. However, we confirmed that small glass frit used pastes have narrow sintering window by rapid completion of sintering densification.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.37-41
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• 2004

As mobile communication devices use wide bands for large data transmission, Low Temperature Co-fired Ceramic(LTCC) has been a candidate for module substrate, for it provides better electrical properties and enables various embedded passive devices compared to conventional PCB. The LTCC, however, has applied in limited area because of non-uniform shrinkage. Hybrid heating was developed to raise sample temperature uniformly in a short period of time This leads to unidirectional sintering which enables sample to be sintered layer by layer from the bottom, resulting in more stable shape of interconnection at the top surface of the sample than conventional electric furnace heating. When sintering properties of substrate and electrical/mechanical properties of interconnection were compared, hybrid heating showed possibility to be applicable to substrate miniaturization and interconnection densification superior to electric furnace heating.