本研究以固態反應法和燒結的方式製作CaCu3Ti4O12和含銅尖晶石鐵氧磁體，藉由改變配方或熱處理條件，使已具有高電容量或是高導磁係數的材料同時具有變阻性質，以整合變阻器和電感或是電容元件的防靜電脈衝(ESD)和抗電磁干擾(EMI)功能。CaCu3Ti4O12和含銅尖晶石鐵氧磁體在經過特定的熱處理後會產生異常晶粒成長的現象，此時晶粒內部份的銅離子會析出到晶粒邊界。這些位於晶粒邊界的富銅二次相為p型導電物質，可與n型半導體CaCu3Ti4O12晶粒或是鐵氧磁體晶粒形成蕭特基能障，進而使試片具有變阻性質。除了利用銅離子析出至晶粒邊界以提高晶粒邊界的受體濃度，也可添加氧化鉍於含鐵量較高的鐵氧磁體中，藉由氧化鉍與含鐵量較高的鐵氧磁體在高溫時會產生化學反應，導致靠近晶粒邊界的鐵氧磁體的含鐵量減少，使靠近晶粒邊界的鐵氧磁體的導電機構從n型轉變成p型。適當的配方及熱處理條件可以促進晶粒邊界形成蕭特基能障，進而使電容器或是電感器同時具有變阻器的功能。整合兩種元件的功能後，可降低終端電子產品的生產成本和體積。

CaCu3Ti4O12 and two kinds of copper-containing spinel ferrites were treated with different thermal process to make a material exhibiting simultaneous capacitor or inductor and varistor properties. Varistor and EMI filter can be integrated by using varistor-magnetic or varistor-dielectric materials to protect other components from electro-static discharge (ESD) and decrease electromagnetic interference (EMI) simultaneously. Integrating different kinds of passive components can reduce the final product size. The relationship between the grain-boundary composition and varistor properties were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersion spectroscopy (EDS), and X-ray photoelectric spectroscopy (XPS). Abnormal grain growth occurs after specific sintering processes in CaCu3Ti4O12 and copper spinel ferrite. After abnormal grain growth, copper oxides would precipitate at grain-boundary or triple junction. The copper oxides would develop at the grain boundary as the acceptor state, forming double Schottky barriers with the n-type semiconductor grains, causing the specimens exhibit varistor property. Except using copper oxides precipitate at grain-boundary to form Schottky barrier, iron-rich ferrites added with bismuth oxide treated with suitable thermal process also can form Schottky barrier. The experimental results showed that Bi2O3 reacted and diffused into the spinel ferrite grain, forming bismuth iron compounds, causing the chemical composition near grain-boundary become iron deficient. The Fe deficiency spinel ferrite near the grain-boundary then changed to p-type conduction. The combination of the n-type semi-conductive grain interior and p-type spinel ferrite near the grain-boundary can form a double Schottky barrier, leading the specimen to exhibit varistor properties.

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