本實驗使用溶膠凝膠法(sol-gel)來製備摻雜鎳的鐵酸鉍。以溶膠凝膠法製得的粉末再經過燒結，製備塊材的樣品。由實驗可發現摻雜鎳的鐵酸鉍可由控制不同的燒結溫度來獲得鐵酸鉍的成相，避免Bi25FeO40和Bi2Fe4O9的雜相的生成。隨著鎳摻雜濃度的提高至5at%，雜相Bi25FeO40的生成將不可避免。而由磁滯曲線的量測，摻雜高於3at% Ni的樣品可以發現磁性相，推測可能為Ni2FeO4相。
藉由光致發光量測之發光光譜，摻雜鎳的鐵酸鉍可以觀察到452nm、468nm、512nm、680nm和689nm等發光波段。其中452nm為導帶至價帶之躍遷，468nm可能來自Bi2+缺陷能階至價帶之躍遷，而512nm可視為導帶至Ni3+能階，680nm和689nm應該與氧空缺有關。在導電率對溫度的量測方面，觀察到鐵酸鉍的電阻隨溫度上升而下降的現象，經過公式的換算可得摻雜鎳鐵酸鉍之活化能。其中活化能2.43eV符合光致光譜觀察到512nm發光波段之能量，說明可能有Ni3+能階的存在。
以本製程製作的樣品進行I-V特性分析，由擬合圖可以觀察到在低電位為歐姆導體的狀態，而高電位則是受空間電荷所主導。在照光下動態電位電流變化的實驗中，可以發現無摻雜和摻雜鎳鐵酸鉍皆具有鐵電體光伏效應的性質，但有摻雜鎳的鐵酸鉍樣品的電流較無摻雜的樣品強度高約一個數量級。

In this study, Ni-doped bismuth ferrite was prepared by the sol–gel method. Under the optimized sintering conditions, the samples with the Ni concentration less than 3 at% showed a pure phase. For the higher doping concentration, X-ray diffraction (XRD) revealed the presence of the secondary phase, Bi25FeO40, and the samples showed a large magnetic moment with a typical M-H hysteresis loop for the soft ferromagnets. Considering the earlier XRD observation of the Bi-enriched secondary phase, the formation of the spinel ferrite NiFe2O4 was highly likely, indicating that the Ni doping limit in BiFeO3 was below 3 at%.
Photoluminescence measurements were carried out for the samples and observed five emissions at the wavelengths about 452 nm, 468 nm, 512nm, 680nm and 689 nm, respectively. The 452 nm emission came from the inter-band transition and the 469 nm emission was probably due to the transition from the Bi2+ defect level to the valence band. The 512nm emission was identified with the transition from the conduction band to the Ni3+ level. The 680nm and 689nm emissions were related to the oxygen vacancies. Compared to the pure BiFeO3, the resistivity of the Ni-doped BiFeO3 samples were reduced by more than three orders of magnitude. In the temperature-dependent measurements, the resistivity decreased with the increasing temperature and the activation energies of the Ni-doped BiFeO3 were obtained by fitting the Arrhenius plots. The observed activation energy of 2.43 eV could be related to the 512nm emission. The origin of this defect/dopant level might be ascribed to the presence of Ni3+.
The current vs. voltage (I-V) characteristics were analyzed. The initial low voltage part of the I-V curves was ohmic, while in the high voltage region the power law relations (IVn, n>1) were observed, indicating that the dominant conduction mechanism was the space charge limited conduction with deep traps. Under the simulated-sunlight illumination, photovoltaic effect was observed for both the pure and Ni-doped BiFeO3. However, the magnitude of the effect was ten-fold larger for the Ni doped samples.

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