Na掺杂对单畴YBCO超导块材性能的影响
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摘要
高温超导经过二十余年的发展,氧化物超导块材取得了很大的进展,主要是围绕着Y系材料展开的。单畴的YBCO超导材料以其较高的Tc、Jc和大的磁悬浮力而受到普遍关注。本文主要研究Na掺杂对单畴YBCO超导块材性能的影响以及新型第二相粒子Y_2Ba_4CuNbO_x粉体的制备。
本文采用固相烧结法制备掺Na的YBCO粉体和YbBCO初始粉体,通过顶部籽晶熔融织构工艺制备出具有不同Na含量的YBCO超导块材,同时对该类超导材料的显微结构和磁悬浮力等性能进行了分析;其次,对新型第二相粒子Y_2Ba_4CuNbO_x粉体的制备作了初步的研究,分析了其物相成分、相变过程、微观形貌、碳含量等,确定了制备该类粉体的合成温度。
在制备掺Na的单畴YBCO超导块材之前,需要用到YBa_(2-x)Na_xCu_3O_(7-δ)(x=0、0.05、0.1、0.15、0.2、0.25、0.3),Y_2BaCuO_5,Yb_(1.8)Ba_(2.4)Cu_(3.4)O_y三种粉体,其制备方法为固态反应法,采用四次球磨,三次烧结的步骤,三种粉体的烧结温度分别为940℃,920℃,910℃,三次烧结时间均为24小时。
Na掺杂对单畴YBCO超导块材的影响研究方面,主要研究了不同Na含量对YBCO初始粉体的织构度、相结构、晶格参数的影响;以及Na的含量对单畴YBCO超导块材宏观形貌、显微结构、磁悬浮力的影响等方面。XRD分析表明,对于YBa_(2-x)Na_xCu_3O_(7-δ)(x=0、0.05、0.1、0.15、0.2、0.25、0.3)粉体而言,随着Na掺杂量的增加,YBCO粉末(00l)面择优取向生长,烧结体织构度显著提高。通过对此系列单畴YBCO超导样品的宏观形貌和磁悬浮力的观察与测量发现,Na掺杂的YBCO超导块材均能长出单畴样品,而且随着Na掺杂量的增加,样品在x=0.2时磁悬浮力最大。SEM对样品的显微结构分析发现,随着Na含量的增加,YBCO超导片层厚度增加,Y211粒子x>0.2时明显长大。通过对样品晶体生长前沿成份的EDX分析发现,当Cu元素比例多,Y、Ba元素比例少的时候,块材停止生长。
通过热分析发现,当用金属氧化物合成的Y_2Ba_4CuNbO_x粉体时,DTA曲线中存在5个吸热峰,对应的温度分别为820℃、950℃、970℃、1020℃、1100℃,生成的化合物分别为BaCuO_2(011相)、YBa_2Cu_3O_(7-δ)(123相)、BaNbO_3、Y_2BaCuO_5(211相)、Y_2Ba_4CuNbO_x(2411相);通过对不同的烧结温度下(1110℃～1150℃)制成的Y_2Ba_4CuNbO_x粉体研究发现,当烧结温度为1150℃时,可获得XRD纯的Y_2Ba_4CuNbO_x(2411相)。
High-temperature oxide superconductor materials have made very great progress in last 20 years, and the efforts in this direction are mainly around Y-based material. Single domain YBCO bulk superconductors are highly appreciated because of their higher Tc, Jc and levitation force. This paper mainly studied properties of Na-doped single-domain YBCO bulk superconductors, and the fabrication of Y_2Ba_4CuNbO_x powders with XRD purity.
In this paper, the initial Na-doped YBCO and YbBCO powders were composited by the solidstate reaction method. YBCO bulk superconductors with different Na content were prepared by top seeded melt texturing growth technique, meanwhile, their microstructure and levitation force were analyzed systematically. Secondly, the fabrication of Y_2Ba_4CuNbO_x powders were studied preliminary, including phase composition, microstructure, carbon content, and the most appropriate synthesis temperature of the powders was established.
Before preparation of the Na-doped YBCO bulk superconductor, YBa_(2-x)Na_xCu_3O_(7-δ) (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3), Y_2BaCuO_5, Yb_(1.8)Ba_(2.4)Cu_(3.4)O_y, powders were synthesized firstly. The above-mentioned powders were sintered by solid-state reaction methods. The powders were sintered at temperature of 940℃, 920℃, 910℃for 24h and three times respectively, with an interval of ball milling after each sintering process.
During the preparation of Na-doped YBCO bulk superconductors by the top seed melting texture growth method, the effect of Na-addition on the phase structure, lattice parameters of the Na-doped YBCO powder, the microstructure and levitation force of the YBCO single domain bulk superconductor were studied. In terms of YBa_(2-x)Na_xCu_3O_(7-δ)(x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) , with the increasing of Na-addition, XRD results showed that texture degree of YBCO sintered powder was improved significantly, and the diffraction angle was moved to the higher degree. SEM obseration found that the YBCO layers grew thicker, and Y211 particles grew bigger while x>0.2. In the meantime, the levitation force was measured systematically. The total area of single domain was increasing gradually with the increasing of the Na addition, the levitation force achived a largest value when x=0.2. Though the EDX analysis, indicated that the growth of single domain of YBCO bulk would be limited when the chemical composition in the liquid ahead of the YBCO crystal growth frontier was depleted in yttrium and barium.
During the preparation of Y_2Ba_4CuNbO_x powders, the DTA result indicated that there are five endothermic peaks appeared near 820℃, 950℃, 970℃, 1020℃, 1100℃, each corresponding to production of new material; Y_2Ba_4CuNbO_x samples were prepared at different temperatures (1110℃～1150℃), the phase compositions and crystal structure of the samples were analyzed by X-ray diffraction (XRD). It was found that XRD purity of Y_2Ba_4CuNbO_x powder could be synthesized when the sample was sintered at 1150℃.
本文采用固相烧结法制备掺Na的YBCO粉体和YbBCO初始粉体,通过顶部籽晶熔融织构工艺制备出具有不同Na含量的YBCO超导块材,同时对该类超导材料的显微结构和磁悬浮力等性能进行了分析;其次,对新型第二相粒子Y_2Ba_4CuNbO_x粉体的制备作了初步的研究,分析了其物相成分、相变过程、微观形貌、碳含量等,确定了制备该类粉体的合成温度。
在制备掺Na的单畴YBCO超导块材之前,需要用到YBa_(2-x)Na_xCu_3O_(7-δ)(x=0、0.05、0.1、0.15、0.2、0.25、0.3),Y_2BaCuO_5,Yb_(1.8)Ba_(2.4)Cu_(3.4)O_y三种粉体,其制备方法为固态反应法,采用四次球磨,三次烧结的步骤,三种粉体的烧结温度分别为940℃,920℃,910℃,三次烧结时间均为24小时。
Na掺杂对单畴YBCO超导块材的影响研究方面,主要研究了不同Na含量对YBCO初始粉体的织构度、相结构、晶格参数的影响;以及Na的含量对单畴YBCO超导块材宏观形貌、显微结构、磁悬浮力的影响等方面。XRD分析表明,对于YBa_(2-x)Na_xCu_3O_(7-δ)(x=0、0.05、0.1、0.15、0.2、0.25、0.3)粉体而言,随着Na掺杂量的增加,YBCO粉末(00l)面择优取向生长,烧结体织构度显著提高。通过对此系列单畴YBCO超导样品的宏观形貌和磁悬浮力的观察与测量发现,Na掺杂的YBCO超导块材均能长出单畴样品,而且随着Na掺杂量的增加,样品在x=0.2时磁悬浮力最大。SEM对样品的显微结构分析发现,随着Na含量的增加,YBCO超导片层厚度增加,Y211粒子x>0.2时明显长大。通过对样品晶体生长前沿成份的EDX分析发现,当Cu元素比例多,Y、Ba元素比例少的时候,块材停止生长。
通过热分析发现,当用金属氧化物合成的Y_2Ba_4CuNbO_x粉体时,DTA曲线中存在5个吸热峰,对应的温度分别为820℃、950℃、970℃、1020℃、1100℃,生成的化合物分别为BaCuO_2(011相)、YBa_2Cu_3O_(7-δ)(123相)、BaNbO_3、Y_2BaCuO_5(211相)、Y_2Ba_4CuNbO_x(2411相);通过对不同的烧结温度下(1110℃～1150℃)制成的Y_2Ba_4CuNbO_x粉体研究发现,当烧结温度为1150℃时,可获得XRD纯的Y_2Ba_4CuNbO_x(2411相)。
High-temperature oxide superconductor materials have made very great progress in last 20 years, and the efforts in this direction are mainly around Y-based material. Single domain YBCO bulk superconductors are highly appreciated because of their higher Tc, Jc and levitation force. This paper mainly studied properties of Na-doped single-domain YBCO bulk superconductors, and the fabrication of Y_2Ba_4CuNbO_x powders with XRD purity.
In this paper, the initial Na-doped YBCO and YbBCO powders were composited by the solidstate reaction method. YBCO bulk superconductors with different Na content were prepared by top seeded melt texturing growth technique, meanwhile, their microstructure and levitation force were analyzed systematically. Secondly, the fabrication of Y_2Ba_4CuNbO_x powders were studied preliminary, including phase composition, microstructure, carbon content, and the most appropriate synthesis temperature of the powders was established.
Before preparation of the Na-doped YBCO bulk superconductor, YBa_(2-x)Na_xCu_3O_(7-δ) (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3), Y_2BaCuO_5, Yb_(1.8)Ba_(2.4)Cu_(3.4)O_y, powders were synthesized firstly. The above-mentioned powders were sintered by solid-state reaction methods. The powders were sintered at temperature of 940℃, 920℃, 910℃for 24h and three times respectively, with an interval of ball milling after each sintering process.
During the preparation of Na-doped YBCO bulk superconductors by the top seed melting texture growth method, the effect of Na-addition on the phase structure, lattice parameters of the Na-doped YBCO powder, the microstructure and levitation force of the YBCO single domain bulk superconductor were studied. In terms of YBa_(2-x)Na_xCu_3O_(7-δ)(x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) , with the increasing of Na-addition, XRD results showed that texture degree of YBCO sintered powder was improved significantly, and the diffraction angle was moved to the higher degree. SEM obseration found that the YBCO layers grew thicker, and Y211 particles grew bigger while x>0.2. In the meantime, the levitation force was measured systematically. The total area of single domain was increasing gradually with the increasing of the Na addition, the levitation force achived a largest value when x=0.2. Though the EDX analysis, indicated that the growth of single domain of YBCO bulk would be limited when the chemical composition in the liquid ahead of the YBCO crystal growth frontier was depleted in yttrium and barium.
During the preparation of Y_2Ba_4CuNbO_x powders, the DTA result indicated that there are five endothermic peaks appeared near 820℃, 950℃, 970℃, 1020℃, 1100℃, each corresponding to production of new material; Y_2Ba_4CuNbO_x samples were prepared at different temperatures (1110℃～1150℃), the phase compositions and crystal structure of the samples were analyzed by X-ray diffraction (XRD). It was found that XRD purity of Y_2Ba_4CuNbO_x powder could be synthesized when the sample was sintered at 1150℃.
引文
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