本文選題：Bi系超導(dǎo)材料　切入點(diǎn)：Sol-Gel法　出處：《東北大學(xué)》2010年博士論文　論文類型：學(xué)位論文

【摘要】：本文以可溶性金屬硝酸鹽為原料,乙二胺四乙酸為絡(luò)合劑,采用Sol-Gel法制備Bi系氧化物粉體及薄膜。通過對(duì)Sol-Gel法凝膠工藝的優(yōu)化,改進(jìn)粉體相純度及結(jié)晶性；并在此基礎(chǔ)上進(jìn)行了Bi位La微摻雜Bi-2212粉體及Sr位Ca摻雜Bi-2201粉體的摻雜效應(yīng)研究；最后,將較佳的粉體制備工藝應(yīng)用于Bi-2212薄膜的制備。本文具體研究?jī)?nèi)容如下： 1.分別采用Sol-Gel法與PSG法(Pechini型Sol-Gel法)制備Bi-2212粉體材料,分析凝膠化工藝對(duì)超導(dǎo)粉體質(zhì)量的影響。實(shí)驗(yàn)結(jié)果表明,合適的凝膠化過程能夠明顯增強(qiáng)凝膠網(wǎng)絡(luò)強(qiáng)度,減少凝膠中游離金屬離子的數(shù)量,改善金屬離子均一性,從而提高Bi-2212粉體的相純度及結(jié)晶性。同時(shí),合適的凝膠工藝對(duì)保持各金屬元素的比例具有重大意義。由于各金屬離子分布更加均勻、自發(fā)燃燒過程中金屬硝酸鹽分解的更加充分,粉體燒結(jié)性得到改善,因此燒結(jié)時(shí)間由10h減短至5h,可節(jié)約大量能源。 2.采用Sol-Gel法細(xì)致研究了Bi位La微摻雜Bi-2212粉體結(jié)構(gòu)及電學(xué)性能變化,La摻雜x范圍為0.01-0.09。利用TG-DTA曲線對(duì)化學(xué)反應(yīng)過程進(jìn)行分析,利用X射線衍射進(jìn)行相分析,利用標(biāo)準(zhǔn)四引線法測(cè)試電學(xué)特性隨溫度變化曲線(R-乃。實(shí)驗(yàn)結(jié)果表明,摻La后Bi-2212粉體相仍保持正交結(jié)構(gòu),但隨著La摻雜量的增加,a、b軸長(zhǎng)度增加,c軸長(zhǎng)度減小。并且,La的摻雜雖然并未發(fā)生在CuO2面上,但卻影響著Cu02面的電子性質(zhì),對(duì)Bi-2212相的導(dǎo)電特性影響顯著。 3.采用PSG法制備Sr位Ca摻雜Bi-2201粉體,并對(duì)Bi-2201相結(jié)構(gòu)及電學(xué)性能進(jìn)行分析、表征。實(shí)驗(yàn)結(jié)果表明,摻Ca后Bi2Sr2-xCaxCuOy相的較佳燒結(jié)溫度隨著x值的變化而變化。Ca摻雜量在0.6≤x0.7達(dá)到最大,同時(shí)樣品的晶胞參數(shù)a,b,c均隨著x值的增加而減小。根據(jù)R-T測(cè)試結(jié)果可知,Ca的摻雜可將Bi-2201相的超導(dǎo)轉(zhuǎn)變溫度Tc提高至86K。根據(jù)這一實(shí)驗(yàn)結(jié)果,本文提出了Bi-2201相結(jié)構(gòu)變化模型,用以解釋Bi2Sr2-xCaxCuOy相Tc的提高。 4.采用PSG法在STO襯底上制備具有c軸外延取向的Bi-2212薄膜。通過對(duì)Bi系超導(dǎo)粉體制備工藝的細(xì)致研究,得出高質(zhì)量Bi系粉體的制備方法,并將此方法應(yīng)用于Bi-2212薄膜的制備。通過對(duì)薄膜制備工藝的細(xì)致研究得出具有較高質(zhì)量的、c軸外延取向的Bi-2212薄膜。實(shí)驗(yàn)結(jié)果表明,溶膠成分為Bi2Sr2Ca1.05Cu2O8+δ、薄膜經(jīng)150℃-190℃預(yù)處理、經(jīng)835℃燒結(jié)10min所得到的的Bi-2212薄膜具有較高的相純度及較平整、連續(xù)的表面形貌。通過對(duì)薄膜的電學(xué)性能分析得出,不同制備條件對(duì)薄膜的Tc,onset影響較小,但Tc,0變化較大。
[Abstract]:In this paper, Bi based oxide powders and thin films were prepared by Sol-Gel method using soluble metal nitrate as raw material and ethylenediamine tetraacetic acid as complexing agent. The phase purity and crystallinity of the powders were improved by optimizing the gel process of Sol-Gel method. On this basis, the doping effect of Bi-La micro-doped Bi-2212 powder and Sr-Ca-doped Bi-2201 powder was studied. Finally, the better preparation technology was applied to the preparation of Bi-2212 thin film. 1. Bi-2212 powder materials were prepared by Sol-Gel method and Pechini type Sol-Gel method respectively. The effect of gelation process on the quality of superconducting powder was analyzed. The experimental results show that the gel network strength can be significantly enhanced by proper gelation process. Reducing the amount of free metal ions in gel, improving the homogeneity of metal ions, thus improving the phase purity and crystallinity of Bi-2212 powder. The proper gel process is of great significance to maintain the proportion of metal elements. As the distribution of metal ions is more uniform and the decomposition of metal nitrate is more adequate during spontaneous combustion, the sintering properties of the powders are improved. Therefore, the sintering time is reduced from 10 h to 5 h, which can save a lot of energy. 2. The structure and electrical properties of Bi-La microdoped Bi-2212 powder were studied by Sol-Gel method. The range of La doping x was 0.01-0.09.The chemical reaction process was analyzed by TG-DTA curve and the phase was analyzed by X-ray diffraction. The standard four-lead method was used to measure the electrical properties of Bi-2212 powder with temperature. The experimental results showed that the phase of Bi-2212 powder remained orthogonal structure after La doping. However, with the increase of La doping amount, the C axis length decreases with the increase of La doping content, and La doping does not occur on the CuO2 surface, but it affects the electronic properties of the Cu02 plane, which has a significant effect on the conductivity of the Bi-2212 phase. 3. Sr Ca doped Bi-2201 powders were prepared by PSG method, and the phase structure and electrical properties of Bi-2201 were analyzed and characterized. The experimental results showed that the optimum sintering temperature of Bi2Sr2-xCaxCuOy phase changed with the change of x value. The content of Ca doping reached the maximum at 0.6 鈮，

本文編號(hào)：1571369