- 作者: 鄭秀鳳
- 作者服務機構: 國立臺灣師範大學物理學系
- 中文摘要: 本文提出一種等效電路的模式,且應用複變電抗的方法來分析多晶結構之錳鋅系鐵氧磁體的電導特性。鐵氧磁體晶粒本身具半導體性,電阻係數低;晶界則其高電阻係數,在高頻率電場作用下,會產生極化現象。因此,這種鐵氧磁體可用層狀構造來模擬樣品之電導特性。在此模式中,樣品之特性參數,亦即晶粒電阻係數、晶界電阻係數及介電常數,則以複變電抗的方法分析之:此法乃將樣品之電阻及電抗在複數座標繪出,由曲線在實數軸的截距及最高電抗的阻抗值,可求出土述之特性參數。利用此模式及分析方法,配合實驗數據,顯示在添加氧化鈣的錳鋅系鐵氧磁體中,晶界會產生一薄的絕綠層,但晶粒本身仍舊具有低電阻率的性質。另一方面,在經過控制氣體成份燒結出來的樣品中,晶粒電阻率和晶界電阻率都隨著燒結氣體成份的含氧量而改變,亦即含氧量愈高則燒結過的電阻率也愈高,這種現象歸因於亞鐵離子的氧化作用。另外,在燒結後冷卻過程中,由於電子在亞鐵離子與鐵離子之問的躍遷效應,使得晶界易於產生局部氧化現象,更造成晶界電阻率的大幅度增加。
- 英文摘要: Complex impedance technique was used and a model is proposed to analyze the electrical behaviorof polycrystalline MnZn-ferrite. Complicated microstructure of ferrite specimen is simplified by a modelconsisting of cubic grains. An equivalent circuit is thus derived and the characteristic parameters of thematerial are obtained from the intercepts of resistance-reactance plot of the specimen. For specimensdoped with CaO, the grain boundaries act as the insulating layer and bulk materials show much lower re-sistivity. For specimens sintered under controlled atmosphere, both the bulk material and grain boundaryresistivity increase when oxygen partial pressure (P0) level of the sintering atmosphere is higher. Theincrease in resistivity of the two phases is ascribed to the oxidation of ferrous (Fe) ions. The change inresistivity is more prominent in grain boundary phases. It is ascribed to the preferential oxidation alonggrain boundaries which occurred during cooling period of sintering cycle.
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