(R1-xCax)Ba2Cu3Oy (R = Ho, Er, Tm, Yb)化合物的製備與性質研究

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题名:	(R1-xCax)Ba2Cu3Oy (R = Ho, Er, Tm, Yb)化合物的製備與性質研究
其它题名:	Preparation and properties of (R1-xCax)Ba2Cu3O7 (R = Ho, Er, Tm, Yb) compounds
作者:	顏嘉興;Yam, Jia-hsing
贡献者:	淡江大學化學學系碩士班高惠春;Kao, Huey-chuen I.
关键词:	鈣取代;鈦酸鈣結構;電洞濃度;Ca substitution;RBa2Cu3Oy;hole concentration;XANES spectra
日期:	2008
上传时间:	2010-01-11 02:50:22 (UTC+8)
摘要:	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.
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