BiFeO3(統稱BFO)具有很高的居禮溫度TC(~850℃)和尼爾溫度TN(~370℃)，在室溫下同時擁有鐵電性和反鐵磁性質，是目前最富潛力的複鐵性材料之一。但因其較大漏電流和製程產生之雜相，使其鐵電性質較差。
本論文探討BFO分別以La取代Bi和Ti取代Fe，對BFO性質的影響與改變。Bi3+離子和La3+離子半徑相近，Ti4+離子和Fe3+離子半徑亦相近，故本論文希望在BFO鈣鈦礦結構中，藉由La3+離子取代Bi3+離子和Ti4+離子取代Fe3+離子來改善BFO漏電流過大的問題。
　　我們利用固態反應法製作出BFO塊材和分別摻雜La3+離子和Ti4+離子的BFO塊材，利用導電率量測、漏電流量測、XRD、XPS，並輔以第一原理計算缺陷形成能、bader charge、能態密度(Density of state)，探討不同元素摻雜對BFO其缺陷形成與漏電流機制的影響。

BiFeO3 (BFO), which is one of the most potential multiferroics ,has high Curie temperature TC(~1100 K) and high Néel temperature TN(~643 K) resulting to the coexistence of ferroelectricity and ferromagnetism at room temperature.
This study mainly reported the influence and change by the doping of lanthanum and Titanium.Bi3+ ions have close size as La3+ ions, and Fe3+ ions have close size as Ti4+ ions, so we hope to reduce the leakage current with the substitution of La3+ ions for Bi3+ ions and Ti4+ ions for Fe3+ ions in the perovskite BiFeO3 structure.
Bulks of BiFeO¬3 and BiFeO3 doping with La3+ or Ti4+ were prepared by the usual solid state reaction method. X-ray diffraction(XRD), conductivity measurements ,leakage current measurements, X-ray photoelectron spectroscopy(XPS) are utilized and supplemented by first-principles calculation of defect formation energies, Bader charge, the density of states (DOS),to discuss its impact on the BFO leakage defect formation mechanisms with different doping.

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