釔鋇銅鐵氧(YBaCuFeO5)實際上是超導體釔鋇銅氧(YBaCu5O5)摻雜了三價的鐵離子進去，鐵離子會取代部份的銅離子，而其取代的方式究竟為銅、鐵原子有序排列還是無序排列將造成的結構之空間群為P4/mmm(中心對稱)亦或是P4mm(非中心對稱)。

本論文內容分為兩個部分，第一個部分為在室溫環境中研究釔鋇銅鐵氧(YBaCuFeO5)，在靠近銅和鐵的K吸收邊附近，其能量分別為8.9945keV與7.1305keV，做共振與非共振多光繞射的實驗。第二個部分為在低溫環境中研究
釔鋇銅鐵氧(YBaCuFeO5)，由於其在降溫至175K以下時將出現磁相變以及電性的極化，因此分別選取在相變前即相變後兩個溫度做共振與非共振多光繞射的實驗以觀察結構是否有所改變。上述實驗內容是透過國家同步輻射中心之07A光束線以及Spring8的12B光束線所完成。

最後藉由實驗結果與搭配動力繞射理論計算之結果比較，可確認出釔鋇銅鐵氧(YBaCuFeO_5)是為P4/mmm之結構且是銅、鐵原子不共享同一個晶格位置的情況。另外，在175K以下時釔鋇銅鐵氧(YBaCuFeO5)之磁相變並不伴隨結構變化。

The YBaCuFeO5 is the superconductor YBaCu5O5 doped with Fe3+,where Fe3+ replaces Cu2+ in an ordered or disordered manner,
depending on the crystal structural arrangement. This makes the space group of YBaCuFeO5 is either P4/mmm or P4mm.

The work of this thesis is divided into two parts. First,using multi-beam resonant X-ray diffraction analyzes the structure of YBaCuFeO5 at room temperature when the photon energies are on Cu and Fe K-edges.
Second,the magnetic phase transition and the electrical polarization of YBaCuFeO5 occur when the temperature is dropped to 175K or less. At we use multi-beam resonant or non-resonant X-ray diffraction to analyze the structure of YBaCuFeO5.The experiments were carried out at 100K and 250K,using beam-line 07A of NSRRC and 12B of spring8 .

We have shown that the space group of YBaCuFeO5 is P4/mmm based on the comparison of the experimental results and the calculations with the dynamical diffraction theory. Also it is proved that Cu and Fe do not share the same site positions and the magnetic phase transition cannot influence the structure of YBaCuFeO5.

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[3] Shih-Lin Chang, Special Topics on X-ray Diffraction.

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