【摘要】 利用硝酸盐为起始原料,硝酸为氧化物,柠檬酸为络合剂和燃料,氨水为酸碱中和剂,制备了稳定的柠檬酸盐络合物。柠檬酸盐络合物经高温燃烧分解,获得了YBCO粉体。粉体在960℃氧气条件下退火8小时后压制成块再在960℃氧气条件下退火7小时。利用X-射线对块体进行物相分析,利用标准四接线柱法对块体进行R-T分析,结果发现有比较纯的相,根据Scherrer公式计算得到样品的平均晶粒尺寸约为18nm,起始转变温度约为84.9K,表现出良好的超导电性,并且我们从理论上预言了整个化学反应过程的机理,得出结论:反应物中的柠檬酸与金属阳离子的物质的量之比应不低于0.722。实验结果与理论分析完全一致。更多还原

【Abstract】 With nitrates as original material,nitric acid as oxide,citric acid as complexing agent and fuel,and ammonia as neutralizing agent,stable citrate complexes were prepared,citrate complexes were decomposed at high temperature,and ultra-fine YBCO powders were fabricated later.The powders were annealed in O2 at 960℃ for 8 hours then for 7 hours for YBCO briquetting.The briquetting is examined by X-ray diffraction and normal four terminals method.The results indicate that the briquetting has a pure YBCO phase,the mean grains size is about 18nm,which is calculated by the Scherrer’s equation,the Tc is about 84.9 K.It represents good superconductivity,and we predict the mechanism of the course of the reaction,we get the conclusion: the mol ratio of the citric acid and these metal cations in the reactant should be more than 0.722.The theoretical result agrees well with the experimental one.更多还原