超导材料YBCO的制备及性质研究

【作者】 刘秀兰；

【导师】 赵晓鹏；

【作者基本信息】 西北工业大学 ， 材料物理与化学， 2005， 硕士

【摘要】 超导材料是一种具有零电阻特性和麦斯纳(Meissner)效应的材料。在通常状态下超导材料是绝缘体或半导体,在低温状态下表现出其零电阻特性。超导材料分为低温超导材料和高温超导材料,40K是其分界点。高温超导体中YBCO转变温度最先达到90K,为高温超导的实用化提供了广阔的前景。本项研究分别采用了干法和湿法中的溶胶-凝胶法,并在此基础上进行了改进,采取了不同的制备工艺,研究了O2含量、烧结时间、退火温度等条件对超导性质的影响。首先利用不同通氧量制备烧结了YBCO块材,用XRD等手段表征。结果表明,通氧量为35-40ml/min为最佳,氧含量为0时,所得样品为完全不超导相;氧含量过高时,劈裂峰不够完全。其次,改变烧结时间的长短所得到样品的性质有所不同,烧结时间过短会导致烧结不完全,只出现不超导相。原则上,烧结时间越长越好,但由于反应周期的限制,我们一般采用的较好烧结时间为3天;退火温度的高低及速度不同,所得到的样品性质不同。通过实验探索,最佳退火温度为960℃,退火速率为10℃/min,XRD图中出现2θ为32. 5左右时的主峰劈裂。在超导体的晶体结构中造成某种缺陷,能够提高他们在无阻时的载流能力将纳米棒放入超导结构中会将超导体电流提高10倍。本论文还对ZnO纳米棒的制备中对反应温度、反应时间、超声等影响因素进行了研究。在初始反应时,采用低温冰浴较之常温反应生成的纳米棒直径和长度都小,采用低温冰浴所得ZnO纳米棒的直径100nm,长度约1 μ m,而未利用冰浴的产物直径为1 μ m,长度为10 μ m;表面活性剂的用量越少,反应后所得棒的长度也越小,在所实验的样品中,表面活性剂含量为5%时长径比最佳;回流时间以7h左右为好,反应过程中采取超声方法所得产物的形貌和尺寸比未经过超声的均匀。更多还原

【Abstract】 Superconductors are materials those have zero resistance and Meissner effect when they are in the low temperature. If the critical temperature is low than 40K,we call it low temperature superconductor, or it is high temperature supercondctor. The critical temperature of YBCO firstly reached 90K.We study the effect of O2 ontent, sintering time and annealling temperature to the sample.Firstly, Changing the sintering temperature can change the properties of YBCO.when the sintering temperature is low,the samples are non-supercondctive,and their color is green or gray.And we consider 960℃ is the appropriate temperature,the samples are black.In the XRD the primary peak appeared, it’s superconductive. The annealling time also effects the material of YBCO.If the annealling time is too short, the chemical reaction cannot be completely, the time is longer, and the properties are best. But the reaction period is too long, so we adopted 3 days.Disfigurement can improve the Jc of superconductors when they are adulterated into the crystalloid. So ZnO nanorods are also studied in the research. At low temperature, the ZnO nanorods were synthesized by the refluxing method in the presence of DBS (Dodecyl benzene sulfonic acid sodiumsalt). The samples were characterized by SEM, optics microscopy and XRD techniques. It was found that the parameters including the temperature, the content of surfactant, the ultrasonic and refluxing time had important influence on the formation of the ZnO nanorods. Compared with other methods, that used ultrasonic and low temperature conditions were key to form uniform ZnO nanorods with smaller diameter.更多还原