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Please use this identifier to cite or link to this item:
https://tkuir.lib.tku.edu.tw/dspace/handle/987654321/32842
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| Title: | (R1-xCax)Ba2Cu3Oy (R = Ho, Er, Tm, Yb)化合物的製備與性質研究 |
| Other Titles: | Preparation and properties of (R1-xCax)Ba2Cu3O7 (R = Ho, Er, Tm, Yb) compounds |
| Authors: | 顏嘉興;Yam, Jia-hsing |
| Contributors: | 淡江大學化學學系碩士班
高惠春;Kao, Huey-chuen I. |
| Keywords: | 鈣取代;鈦酸鈣結構;電洞濃度;Ca substitution;RBa2Cu3Oy;hole concentration;XANES spectra |
| Date: | 2008 |
| Issue Date: | 2010-01-11 02:50:22 (UTC+8) |
| Abstract: | 本研究主要是利用Ca來取代四種三層鈦酸鈣結構中稀土(R)原子之系列樣品 (R1-xCax)Ba2Cu3Oy (R = Ho, Er, Tm, Yb; 0 ≤ x ≤ 0.175，以下簡
稱R123 樣品)。經由Rietveld 精算可算出單位晶胞的a、b 與c 軸長，四
系列之a、c 軸隨著取代量x 增加而變大，b 軸與正交係數則隨著取代量
x 增加而變小，體積隨著取代量增加而膨脹。透過碘滴定法分析四系列
樣品可計算出樣品之氧含量y 隨著取代量x 增加而下降，電洞濃度隨著
取代量的增加會變大至一最大值之後變小，不過計算出之psh (Cu-O 面
的電洞濃度)隨著取代量變大而增加，顯示Ca 取代R 是電洞摻雜，而且
超導轉變溫度Tc 都在取代量x = 0 時最高，隨著取代量x 之增加而降低，
為over doping。XANES 吸收光譜(Cu 的L -edge 和 O 的K- edge)所得到
之Cu3+與CuO2 面的氧原子的強度趨勢與碘滴定法得到的電洞濃度變化
之趨勢相符。當氧含量與正交性較大，Ca 取代量與電洞濃度psh 較小時
會有較高的超導轉移溫度Tc。稀土元素之大小在本系列之中較無影響
A series of samples with normal compositions as (R1-xCax)Ba2Cu3Oy were prepared by a conventional solid state reaction method with 0≦x≦0.175 (Yb series: 0.025≦x≦0.175). Unit-cell a- and c-axis increase and b-axis decreases with increasing the amount of Ca substitution, thus, orthorhombicity decreases as x increases. Both Tc and y decrease with x. However, psh increases with x, which shows a hole doping effect caused by the substitution of Ca2+ with R3+ cation. Hole concentrations obtained from the iodometric titration coincide with the results observed by O K- and Cu L- edge XANES spectra. For the all series samples, the highest Tc is found with x = 0 sample. With x, y, p, Tc and orthorhombicity, we have higher Tc when x and psh decrease; y and orthorhombicity increase. No obvious difference is found in different R cation. |
| Appears in Collections: | [Graduate Institute & Department of Chemistry] Thesis
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