• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.4
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• pp.332-336
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• 2007

In this study, multilayer piezoelectric transformer was manufactured using the PMN-PNN-PZT ceramic and then the electrical characteristics were investigated according to the variations of frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at the vicinity of 75 kHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, the multilayer piezoelectric transformer showed the temperature rise of less than $20^{\circ}C$ at the output power of 20 W. As the results, the multilayer piezoelectric transformer manufactured at low co-firing temperature of $940^{\circ}C$ using PMN-PNN-PZT ceramics could be stably driven as the step-down transformers.

• Journal of Powder Materials
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• v.7 no.4
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• pp.218-227
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• 2000

It is well known that the Cu-Cr alloys are very difficult to be made by conventional sintering methods. This difficulty originates both from limited solubility of Cr in the Cu matrix and from limited sintering temperature due to high vapor pressures of Cr and Cu components at the high temperature. Densification of Cu-50%Cr Powder compacts by conventional Powder metallurgy Process has been studied. Three kinds of sintering methods were tested in order to obtain high-density sintered compacts. Completely densified Cu-Cr compacts could be obtained neither by solid state sintering method nor by liquid phase sintering method. Both low degree of shrinkage and evolution of large pores in the Cu matrix during the solid state sintering are attributed to the anchoring effect of large Cr particles, which inhibits homogeneous densification of Cu matrix and induces pore generation in the Cu matrix. In addition, the effect of undiffusible gas coming from the reduction of Cu-oxide and Cr-oxide was observed during liquid phase sintering. A two-step sintering method, solid state sintering followed by liquid phase sintering, was proved to have beneficial effect on the fabrication of high-dendsity Cu-Cr sintered compacts. The sintered compacts have properties similar to those of commercial products.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.289-295
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• 1997

Effect of ceramic processing was investigated on the microstructure and electronic properties of low loss Mn-Zn ferrite. Addition of CaO and SiO2 to calcined powder rather than to raw materials mixtured resulted in finer-grained microstructure. Higher oxygen pressure during sintering caused microstructural inhomogeneity and the increase in power loss and disaccommodation factor. Relatively low power loss was found for sintering up to 130$0^{\circ}C$ from powders calcined at high temperature and milled shortly. It was caused by slow densification rate and normal grain growth up to 130$0^{\circ}C$. Calcination at low temperature and prolonged milling enhanced den-sification, which gave a fine grained microstructure and low powder loss at sintering temperture below 120$0^{\circ}C$. Sintering temperature above 125$0^{\circ}C$, however, showed abnormal grain growth.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1250-1251
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• 2008

In this study, the dielectric ceramics with low loss were investigated for high frequency application. All sample of the $Ba_5M_4O_{15}$ (M=Ta, Nb) ceramics were prepared by the conventional mixed oxide method and sintered at $1325{\sim}1575^{\circ}C$. The bulk density and dielectric constant of the $Ba_5Ta_4O_{15}$ ceramics were increased continuously with increasing of sintering temperature. The quality factor was increased in the sintering temperature of $1375{\sim}1475^{\circ}C$ but decreased at the temperature above 1475$^{\circ}C$. In the case of $Ba_5Nb_4O_{15}$ ceramics, the bulk density, dielectric constant and quality factor were increased with sintering temperature but decreased above temperature of 1400$^{\circ}C$. The dielectric constant, quality factor and temperature coefficient of the resonant frequency (TCRF) of the $Ba_5Ta_4O_{15}$ and $Ba_5Nb_4O_{15}$ ceramics, sintered at 1475$^{\circ}C$ and 1400$^{\circ}C$, were 25.15, 53105 GHz, -3.06 ppm/$^{\circ}C$ and 39.55, 28052 GHz, 5.7 ppm/$^{\circ}C$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.4
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• pp.282-285
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• 2012

It is well known that Zinc Oxide (ZnO) is an attractive material for its various applications. ZnO has been mostly used as a transparent conducting oxide in liquid crystal displays, solar cells due to its advantages of low cost, high productivity, and excellent electrical conductivity. Notably, flexible-dye-sensitized solar cells (DSSCs) based on polyethylene terephthalate (PET) substrates require low temperature sintering processing conditions. Therefore, low temperature processing conditions have been strongly required for transparent conducting film applications. In this paper, we prepared low temperature-sintered ZnO ceramics employing Li as a sintering aid.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.10
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• pp.608-612
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• 2016

In this study, in order to develop relaxor ferroelectric ceramics for refrigeration device application with large electrocaloric effect and low sintering temperature, PLZT(8/65/35) ceramics was fabricated using conventional solid-state method with the variation of sintering temperature ($1,050^{\circ}C$, $1,100^{\circ}C$, $1,200^{\circ}C$). The XRD pattern of all specimens indicated general perovskite structure with secondary phase. From the results of temperature dependence of dielectric constant, the $T_C$ (ferroelectric-paraelectric phase transition temperature) was shifted toward high temperature with increasing sintering temperature. When the specimen was sintered at $1,100^{\circ}C$, the optimal value of ${\Delta}T{\sim}0.349^{\circ}C$ in ambient temperature of $215^{\circ}C$ was appeared. It is considered that PLZT(8/65/35) ceramics possess the possibility of refrigeration device application.

• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.104-110
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• 2019

The low-temperature sintering behavior of AlN was investigated through a conventional method. $CaF_2$, CuO and Cu were selected as additives based on their low melting points. When sintered at $1600^{\circ}C$ for 8 h in $N_2$ atmosphere, a sample density > 98% was obtained. The X-ray data indicated that eutectic reactions below $1200^{\circ}C$ were found. Therefore, the current systems have lower liquid formation temperatures than other systems. The liquid phase showed high dihedral angles at triple grain junctions, indicating that the liquid had poor wettability on the grain surfaces. Eventually, the liquid was likely to vaporize due to the unfavorable wetting condition. As a result, a microstructure with clean grain boundaries was obtained, resulting in higher contiguity between grains. From EDS analysis, oxygen impurity seems to be well removed in AlN lattice. Therefore, it is believed that the current systems are beneficial for reducing sintering temperature and improving oxygen removal.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.12
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• pp.149-156
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• 2019

Recently, skyscraper building and apartment fires, which were rapidly spread out from a low floor to a rooftop, have become a frequent occurrence in mass media. This fire problems have a fatal disadvantage that the exterior wall finish of the building emits toxic gas in case of fire by using dry bit method or organic insulating material. Therefore, in order to remedy these problems, many exterior wall finishing construction methods have been proposed, but the current trend is to use existing construction methods due to problems such as economy, weight, and durability. On the other hand, in countries such as Germany and Japan, ceramic sidings are used as exterior finishing material for buildings, which is environmentally friendly, excellent natural beauty, long life, easy maintenance and high-quality exterior materials. However, those ceramic sidings have still the problems such as manufacturing cost and weight problem because of boosting the sintering temperature up to 1,350℃ or more. Also, conventional CRC, MgO, FRP sidings which are composed of pulp, glass fiber and organic materials, have been reports of deformation due to ultraviolet rays, discoloration, corrosion and scattering, surface rupture, lifting and peeling. Therefore, in this study as an alternative to solve this problem, halosite nano kaolin produced in Sancheong in Korea and frit flux were used to satisfy the required properties as ceramic siding using low temperature sintering (below 1,000℃) and lightweight materials such as pearlite. This study aims to design the optimal formulation and process of materials and to study the characteristics of nano-coated ceramic siding material development and to present relevant basic data. The findings show that ceramic siding for nanocoated building materials is excellent as a natural ceramic siding building material. The fire resistance of natural minerals and nano particle refining technology satisfy the bending strength of 80kgf / cm2, the volume ratio of 2.0 and the absorption rate of less than 10.0%.

• Journal of the Korean Ceramic Society
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• v.25 no.1
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• pp.54-58
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• 1988

In order to depress PbO vaporization during calcination and improve sinterability in low temperature, a method for preparing homogeous Lead-Zirconate-Titanate (PZT) powder from aqueous salt solution by precipitation is described. In this method, single phae PZT fine powders are formed at above 500$^{\circ}C$. PZT-ceramics using these powders have high sinterability, and good sintering characteristics relatively low temp. (-high apparent density, low porosity, low water adsorption etc.)

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1099-1102
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• 2004

For the development of Pb-free low temperature sintering glass frits, $BaO-B_2O_3-SiO_2$ system was examined. The content of BaO and $B_2O_3$ was changed when the content of $SiO_2$ was fixed to 10 mol%. When the content of BaO was more than 60 mol% devitrification was observed. In the sintering temperature range between 520${\sim}$620 $^{\circ}C$, the optimum sintering temperature decreased as the content of BaO increased. When BaO ${\geq}$45 mol%, the glasses were crystallized after sintering. Candidate compositions are suggested in $BaO-B_2O_3-SiO_2$ system, which can replace the PbO containing glass system.