自從銅氧化物超導體被發現以來，PrBa2Cu3O7 (Pr123) 一直由於其不超導及其他特殊性質而廣受矚目。近年來在超導的Pr123單晶被合成之後，不但沒有為此領域畫下句點，反而引起更多的爭議，其中一個解釋為什麼Pr123單晶會超導的理由是其超導性可能由於部分富含鋇的區域所形成。為研究此假設之可能性，我們合成了Pr1-xBa2+xCu3O7 (x=1~0.3)的多晶樣品，並以Pr1-xCaxBa2Cu3O7 (x=0~0.6)為對照組。X光近緣吸收光譜顯示了載子濃度隨Ba或Ca的摻雜而增加。此項結果並與電阻率及熱電功率的測量結果一致。然而載子可能以另一種特殊方式摻入而非單純的加在銅氧平面上。

Since the discovery of cuprate superconductors, PrBa2Cu3O7 (Pr123) has attracted much attention due to its nonsuperconductivity and other anomalies. The very recent reports on superconducting Pr123 instead of putting an end of this issue, virtually stimulate more controversies. One of the proposed explanations for the recently observed superconductivity in Pr123 is that the samples could be Ba-rich Pr123 to investigate this possibility, we prepared Pr1-xBa2+xCu3O7 (x=1~0.3) and Pr1-xCaxBa2Cu3O7 (x=0~0.6) as comparison. X-ray absorption near edge spectroscopy (XANES) indicates an increase in carrier concentration with Ba and Ca doping, which is consistent with resistivity and thermoelectric power(TEP) data. However, carriers are introduced in a peculiar why rather than simply add into CuO2 plane.

List of Figures…………………………………………………………………….ii
List of Tables……………………………………………………………………...iii
1. Chapter1 Introduction…………………………..1
2. Chapter2 Experimental details………………….5
2.1 Sample Preparation……………………………………………5
2.2 Sample Characterization………………………………………5
2.3 Electrical resistivity…………………………………………..10
2.4 Thermoelectric Power………………………………………..13
2.5 X-ray absorption near-edge structure spectra (XANES) technique……..16

3. Chapter 3 Result and Discussion……………….25
3.1 X-ray Diffraction (XRD) and crystal structure……………….25
3.2 Resistivity……………………………………………………..38
3.3 XANES analysis………………………………………………42
3.4 Thermoelectric Power Analysis……………………………….49

4. Chapter.4 Summary………………………………53
5. Reference…………………………………………..54

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