The effect of Mg O nano-particles on bi-2223 high temperature superconductors prepared by chemical sol-gel method

The Bi1.7Pb0.3Sr2Ca2Cu3Oδ superconductors were prepared by the sol-gel method and the effect of Mg O nano-particle additive on their properties were studied. Microstructural studies show that the final samples have good homogeneity and are composed of 2223 superconducting phase up to %95 purity. Additionally, the Mg O additives a n mainly distributed as nano-size inclusions on grain boundaries. The penetration considerably increases as the percentage of Mg O additives exceeds 2.5 M A . Electrical measurements revealed that the samples with 2.5 wt% Mg O additive have the highest superconducting temperature, while the superconducting property is weak- for m m Mg O contents. Decrease of superconducting temperature in the presence of high Mg O additives originates from the formation of impure 2212 phase. The results are discussed based on the following two aspects: the effect of additives on the formation of the superconducting phase, and, the role of Mg O nano-particles as pinning centers of magnetic flux