Papers by Author: Seong Jin Hwang

Abstract: Photolithographic process is one of the eco-friendly processes for forming the pattern of the barrier ribs in PDP. Controlling the refractive index of glass is important to develop a photosensitive paste for photolithographic process. We studied the refractive index and the structural transition of these glasses by measuring the refractive index, reflectance, density and dielectric constant with changing the SiO2/B2O3 ratio in the SiO2-B2O3-Al2O3 glass system. The refractive index was investigated to the relationship between the thermal and optical properties depending on the composition. It suggests that the thermal and optical properties in borosilicate glasses should be correlated to the glass structure with the SiO2/B2O3 ratio.

Abstract: The chemical reaction between water and frit surface was determined using pH meter, ICP-MS, zeta-potential analyzer and FT-IR. With increasing the content of barium and boron of glass composition, the difference of water pH increased with different glass systems. During wet milling in aqueous solution, boron and barium of glasses dissolved. The values of zeta potential of lead and bismate frits were negative in water solution. Based on the results, when wet milling is used in water solution, the contents of barium and boron in a glass should be less than 10mol%.

Abstract: For low temperature co-fired ceramics (LTCC) materials, BaO-B2O3-MgO-Al2O3 glass system was tested. The starting temperature for densification of a sintered body was at 700°C and the onset temperature for crystallization of a sintered body was 820°C. With the sintering temperature, the sintered body was investigated with shrinkage, crystal phases, thermal properties, and mechanical properties. The glass transition temperature was constant with increasing frit size. However, the onset point of crystallization increased with increasing frit size. The formation of crystal phase was celsian (BaAl2Si2O8). From our results, it is possible to achieve the glass-ceramic having the high strength and the ability of sintering at low temperature using controlling the sintering temperature of BaO-B2O3-MgO-Al2O3 system glass frit.

Abstract: We investigated the mechanism of chemical reaction between Bi2O3 glass and water solution during milling. As a result, the frit condition affected discoloration with crystallization. After milling, there was a deposited layer on the frit surface. The layer was composed of leached ions, contaminates of metal oxides, and hydroxides. Bismate glass frit is reacted to the milling solution so that the frit surface is formed with a gel layer. In milling, contaminates contained in milling solution is contributed to the formation of deposed layer on frit surface.

Abstract: Oxide glasses having lower glass transition temperature are widely used in electric devices. The oxide glasses usually contain lead oxide. Recently, lead oxide glasses have been replaced with lead-free oxide glasses because of the environmental pollution. We investigated the thermal properties and the glass formation region in the Bi2O3-B2O3-ZnO ternary system. The results showed that the ratio of Tg/Tl of the bismate glasses is around 0.55, which is lower than the value of ratio 0.67, the two-third rule (Tg/ Tl=2/3)

Abstract: The desirable characteristics of the microwave materials include excellent dielectric constant εr, low dielectric loss (high quality factor, Q*f0 value), and small temperature coefficient (~0ppm/°C) of resonant frequency (Tf). The advantages of using a glass-ceramic include shape stability during the sintering stage, improved dielectric properties, mechanical strength, and controlled thermal expansivity. In the present study, glass-ceramic compositions consisting of a glass system (BaO-TiO2-SiO2-Al2O3) and a ceramic filer (BaNd2Ti5O14) were prepared. The glass and glass-ceramic compositions were evaluated for sintering behavior such as shrinkage, densities, thermal properties, and microstructures. In addition, the microwave dielectric properties (≈ 15~20 for εr, > 6000 GHz for Q*f0) were determined by a network analyzer at 6-8 GHz. These results suggest that the compositions can be a candidate for LTCC dielectric materials.

Abstract: A low-temperature co-fired composition with sintering temperature of <900 °C was developed using rare earth derived borate glass (La₂O₃-B₂O₃-TiO₂) and a conventional BNT (BaONd₂O₃-TiO₂) ceramic. The sintering behavior, phase evaluation, sintered morphology, and microwave dielectric properties were investigated. It was found that increasing the sintering temperature from 750 to 850°C leads to increases in shrinkage, densities and microwave dielectric properties (≈ 20 for ε_r and >8000 for Q*f₀). However, after 850 °C , the values of these properties decreased. It is suggested therefore that this new composite has good potential as a new candidate for low temperature co-fired ceramic (LTCC) materials.