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چکیده
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The excess conductivity analysis is used to study the effects of Al2O3–15 wt% ZrO2 (AlZr) nanocomposite on the superconducting properties of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ (BiPb-2223) phase. A series of (BiPb-2223)1-x/ (AlZr)x composite samples (0.0 wt% ≤ x ≤ 1 wt%) were synthesized by the conventional solid-state reaction method. The structural and morphological properties of the synthesized composites were studied using X-ray diffraction and scanning electron microscopy. Results showed that adding AlZr nanocomposite up to 0.5 wt% improves the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ phase formation. The excess conductivity analysis was carried out using Aslamazov–Larkin and Lawrence– Doniach approaches. The results indicated that the Fermi energy EF, Fermi velocity VF, and coherence length along the c axis ξc(0) decrease with increasing the AlZr nanocomposite concentration. The ξc(0) value decreases from 3.68 Å for AlZr free sample to 2.70 Å for x = 1.0 wt%. Moreover, superconducting critical parameters, including lower and upper critical magnetic fields (Bc1(0) and Bc2(0)) and critical current density (Jc(0)), were estimated by the Ginsberg-Landau theory. Obtained values indicated a remarkable enhancement in the mentioned critical parameters by adding the AlZr nanocomposite. The Jc(0) value enhances from 1.4 × 103 A/cm2 for AlZr free sample to 3.5 × 103 A/cm2 for the sample with 1.0 wt% additives, which shows that the Jc(0) is improved by about 150%. In addition, the critical magnetic fields are improved by about 80% in the sample containing 1.0 wt% AlZr compared to the AlZr-free sample. The observed improvement in the superconducting parameters is most likely attributed to the flux pinning capability and intergranular coupling enhancement.
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