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

Preparation and Properties of (R1-xCax)Ba2Cu3O7 (R = Ho, Er, Tm, Yb) compounds

顏嘉興(Jia-Hsing Yam)

指導教授 ： 高惠春

淡江大學/理學院/化學學系碩士班/碩士(2008年)

https://doi.org/10.6846/TKU.2008.00511

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

關鍵字

鈣取代 ； 鈦酸鈣結構 ； 電洞濃度

並列摘要

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.

並列關鍵字

Ca substitution ； RBa2Cu3Oy ； hole concentration ； XANES spectra

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