This study investigated the correlation between the surge energy capability and Bi 2 O 3 volatilization in ZnO varistors by analyzing the volatilization phenomenon of Bi 2 O 3. A ZnO varistor is composed mainly of Sb 2 O 3 , Bi 2 O 3. Bi 2 O 3 has the lowest vapor pressure among these components. Bi 2 O 3 play an important role, moreover, in forming it grain boundaries. These grain boundaries have low conductivity in the leakage current region, but, becomes higher in the region. It also determines the surge energy capability of the varistors. Bismuth oxide has four phases, each with intrinsic ion-conductivity. Formation of the bismuth oxide phase depends on the amount of bismuth at the grain boundary. Volatilization of Bi 2 O 3 should therefore be prevented when developing ZnO varistors was conducted using with high energy capabilities. Analysis of the volatilization phenomenon of Bi 2 O 3 X-ray analysis methods such as X-ray fluorescence, X-ray photoelectron spectroscopy and X-ray diffraction. The results confirmed a close correlation among them. Sealed sintering methods were proposed to prevent the volatilization of Bi 2 O 3 by ZnO varistors.
This study examined the H2 production characteristics from a decomposition reaction using liquid-phase plasma with a bismuth ferrite catalyst. The catalyst was prepared using a sol–gel reaction method. The physicochemical and optical properties of bismuth ferrite were analyzed. H2 production was carried out from a distilled water and aqueous methanol solution by direct irradiation via liquid-phase plasma. The catalyst absorbed visible-light over 610 nm. The measured bandgap of the bismuth ferrite was approximately 2.0 eV. The liquid-phase plasma emitted UV and visible-light simultaneously according to optical emission spectrometry. Bismuth ferrite induced a higher H2 production rate than the TiO2 photocatalyst because it responds to both UV and visible light generated from the liquid-phase plasma.
This study investigates the electrical and physical characteristics of ZnO varistor according to the sintering temperature range from 600 ·C to 1300 ·C. Specimens are prepared with bismuth, antimony and other metal oxides. The composition of ZnO varistor is fixed only one batch. And the microstructure of varistor samples is observed by a FE-SEM & EDS. according to the maximum sintering temperature, the microstructure of ZnO varistors is changed involving both electrical and thermal property changes. Namely, the specimen which has sintering temperature range from 950·C to 1150·Cshows better electrical and thermal properties than the others. Furthermore, Dielectric constant and nonlinear coefficients are strongly influenced by maximum densification temperature.
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