| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 93 === In this research, the reaction layers produced from silver electrode cofired with La-Si-B-O-mullite (LSBM) or Mg-Si-B-Al (MSBA) glass ceramic composites in different sintering conditions were analyzed, and the controlled mechanism was investigated. The grown phases were characterized by X-ray diffractometry (XRD), and the microstructures were studied by scanning and transmission electronic microscopy (SEM and TEM).
In order to study the phenomenon of Ag diffusion into the LSB glass in air, the D-LSBM/Ag laminated samples was sintered at 760oC-840oC and characterized. The activation energy was 246 kJ/mole and the Ag nano-crystals in the sizes between 10~200nm were found appearing in the reaction zone after sintering. Ag, at first, was oxidized in the sintering process, and diffused into the glass. Then Ag nano-particles grow by over-saturation in the glass when cooling. The glass transition temperature (Tg), onset crystallization temperature (To), and the crystallization peak temperature (Tp) decreased because of the Ag diffusion into the glass. The diffusion also degraded the densification, but increased the amount of crystalline phase in the reaction zone. Ag+-ion diffusion in Si-B-O glass was the main controlled mechanism of the formation of reaction zone. However, if the LSBM/Ag sintered in Ar atmosphere, the Ag signal could not be detected on the glass ceramic layer nearby LSBM/Ag interface, and no obvious reaction zone was produced.
On the other hand, when the Ag cofired with MSBA glass ceramic composite, the microstructure of the interface revealed that Ag had diffused into the glass. The reaction of the interface consisted of three zones. Each zone appeared a glass matrix consisting of Ag. But, there was no Ag signal in the crystal phase. The path of the Ag diffusion was gradually blocked by the production of Mg-Al-Si crystalline phase in the zone 1. Because of the Mg content diffused toward electrode, and the slight increase of Al content in zone 2, the Ag concentration in zone 1 and 2 was lower than that in zone 3. The final distribution of Ag concentration didn’t reflect a general diffusion phenomenon.
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