本研究利用燃燒法其製程快速的特點來製備具有鈣鈦礦ABO3結構的非化學劑量比LiNbO3及摻雜Fe之LiNbO3¬粉末，對其表面形貌、缺陷結構變化與鐵磁性等物理性質進行探討，做為多鐵材料的初步開發研究。
本研究利用DSC測得鐵電居理溫度，並透過鐵電居理溫度與Li濃度的關係式來獲得[Li]/([Li]+[Nb])的摩爾數比，其比值為46.55及49.24%。發現燃燒法製程的晶體缺陷結構較多，導致LiNbO3有相分離的現象。摻雜Fe之LiNbO3其摻雜濃度在0.56~3.314 mol%，但隨著摻雜Fe濃度變高，摩爾數比值為46.55%的相會消失，顯示摻雜鐵於LiNbO3¬晶體中會使缺陷較多的相消失進而穩定晶體結構。在表面型貌方面，粉末的晶體尺寸則約為100~200 nm，並不隨Fe的摻雜而有明顯的變化。
本研究先利用不同空缺模型透過Rietveld方法來精算非化學劑量比的LiNbO3結構，發現混合空缺模型及Li空缺模型較合適解釋其缺陷結構，而Nb空缺模型則因為過多的反位鈮(Nb*)存在A位的假設導致結構不合理的扭曲。
同時我們也利用XPS、UV-Vis及Raman光譜分析摻雜Fe之LiNbO3，得知Fe以二價及三價混合進入LiNbO3結構中，取代A位的Li，且無電荷補償現象。在A位中依舊留有Nb*及其空缺，但B位的Nb有位移現象，推估是Nb*被推回B位中。
接著我們再進一步利用混合空缺模型及Li空缺模型合併上述觀察的假設來分析摻雜Fe之LiNbO3晶格結構。其中，混合空缺模型合併部份Nb*被推回B位的假設下的模擬結果，是當中最合適解釋摻雜Fe之 LiNbO3缺陷結構的推論。我們可以發現隨著摻雜Fe濃度越高，O-Nb-O和O-Li/Fe-O鍵角改變而使得Li/Fe-Nb鍵長縮短，LiO6與NbO6兩架構更靠近，不含陽離子的氧八面體(ʋ O6)架構在xy平面上會變細長緊縮，也使Li/Fe的原子位置沿著c軸上升。但同時，隨著摻雜Fe濃度越高，Nb*被推回B位也越多，Nb空缺(VNb)消失越多，則會減緩晶格扭曲，以上因素互相競爭，導致晶格常數變化並不明顯。
本研究發現摻雜Fe之LiNbO3晶體皆具有室溫軟鐵磁性。當摻雜濃度增加至1.3 mol%以上，飽和磁化率呈現非線性的增加，最大的飽和磁化率為1.18 emu/g。另外，矯頑磁場也有非線性增加，最高值為93 Oe，但在3.314 mol%有些微下降。推估是因為Nb*被推回B位越多，Nb空缺(VNb)消失越多，而使Fe-Nb之間的距離縮短，導致整體Fe-Nb自旋耦合將更為強烈，使飽和磁化率有非線性的增加，然而當Fe-Nb太靠近時，矯頑磁場則會些微下降。

In this work, the defect structure and the characterization of the congruent LiNbO3 and Fe-doped LiNbO3 were investigated for the discovery of multiferroic materials.
The nanocrystal size is 100~200 nm. The molar ratio of [Li]/([Li]+[Nb]) determined by Curie temperature via DSC is about 46.55 and 49.24% and the doping concentration of Fe is 0.56~3.314 mol %.
Li vacancy model and the mixed-vacancy model applied in Rietveld refinement of the congruent LiNbO3 lead to reasonable fitting results. Coexistence of Fe+2, Fe+3 and the anti-site Nb (Nb*) in Fe-doped LiNbO3 was probed by XPS and UV-Vis spectra. Raman spectra exhibit the displacement along the c-axis of Li and Nb, and the deformation of the NbO6 framework as Fe is doped into LiNbO3. Rietveld fitting results of Fe-doped LiNbO3 showed that doping Fe could cause the lattice thinner and longer and the assumption of the mixed-vacancy model with the replacement of Li by Fe+2/Fe+3 and then pushing Nb* back to Nb site is more appropriate than the other to describe the structure.
Fe-doped LiNbO3 exhibits room-temperature soft ferromagnetism. The highest coercivity (93 Oe) was obtained as doping Fe is up to 1.856 mol%, and the saturation magnetization increased to 1.18 emu/g as doping Fe is up to 3.314 mol%. This nonlinear increase could be inferred as the increase of Nb* pushing back to Nb site, which resulted in a shorter bonding distance of Fe-Nb and the stronger spin coupling of Fe-Nb in the whole crystal.

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