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Title:	Ac susceptibility and excess conductivity analyses of Bi substituted TlSr2CaCu2o7-δ on Tl site and Te, Cd, Nb and B substituted on Ca site
Authors:	Salha Salem Omar Farhat (P70782)
Supervisor:	Roslan Abd. Shukor, Prof. Dato Dr.
Keywords:	Superconductors Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	1-Aug-2019
Description:	This study involves five different substitutions on the TlSr2CaCu2O7-δ (Tl-l2l2) superconductors; Bi, Te, Cd, Nb and B. The objectives are to determine the superconductivity and formation of the Tl-1212 phase. All samples were synthesized using the solid state reaction method. The X-ray powder diffraction patterns indicated that a single Tl-1212 phase with tetragonal unit cell (space group, P4/mmm) was dominant with few weak diffraction lines of the Tl-1201, and an unknown phase in all samples. The electrical resistance measurements on (Tl1-xBix)Sr2CaCu2O7-δ ( x = 0.1-0.7) series showed the highest Tc onset (101 K) and Tc zero (87 K) at x = 0.3 and 0.4. For Te and Cd substitutions at the Ca site, samples with x = 0.20 and 0.15 showed the highest Tc onset (95 K). The highest volume fraction for Tl-1212 phase in (Tl0.8Bi0.2)Sr2(Ca1-xNbx)Cu2O7-δ was observed at x = 0.10 sample (50%). The temperature dependent electrical resistance measurements on (Tl0.6Bi0.4)Sr2(Ca1-xBx)Cu2O7-δ ( x = 0.05- 0.50) series showed Tc onset increased gradually with x from 89 K (x = 0.05) to 92 K (x = 0.15). Superconducting fluctuation behaviour (SFB) in (Tl1-xBix)Sr2CaCu2O7-δ (x = 0.1-0.7), (Tl0.6Bi0.4)Sr2(Ca1-xTex)Cu2O7-δ (x = 0-0.2) and (Tl0.6Bi0.4)Sr2(Ca1-xCdx)Cu2O7-δ (x = 0-0.15) series was analyzed by using Asmalazov-Larkin (AL) theory as a framework. The (Tl1-xBix)Sr2CaCu2O7-δ series showed the shortest coherence length ξc(0) (0.845 Å) at x = 0.7. This sample also showed the lowest inter-layer coupling, J value (0.282) and the highest anisotropy (γ = 11.83). For (Tl0.6Bi0.4)Sr2(Ca1-xTex)Cu2O7-δ series, the maximum value of anisotropy (γ) was (13.707) at x = 0.2. This sample also showed the highest 2D to 3D transition temperature, T2D-3D (75 K) amongst the samples. A transition from 2D to 3D behaviour was observed as the temperature was decreased for the (Tl0.6Bi0.4)Sr2(Ca1-xCdx)Cu2O7-δ ( x = 0-0.15) series. The highest anisotropy (γ) within the series was 9.692 at x = 0.15. In addition, AC susceptibility measurements in (Tl1-xBix)Sr2CaCu2O7-δ (x = 0.1-0.5), (Tl0.6Bi0.4)Sr2(Ca1-xCdx)Cu2O7-δ (x = 0-0.15), (Tl0.8Bi0.2)Sr2(Ca1-xNbx)Cu2O7-δ (x = 0-0.1) and (Tl0.6Bi0.4)Sr2(Ca1-xBx)Cu2O7-δ ( x = 0.05-0.3) series was analysed by using Bean's Model. This work showed that substitution with multivalent ion at Tl or Ca sites in TlSr2CaCu2O7-δ resulted in the formation of the Tl-1212 phase. The characteristic scaling of the curves obtained from excess conductivity ln(Δζ/ζo) as a function of reduced temperature, ln(ε) for the multivalent ion substitution showed a crossover between two to three-dimensional behaviours around critical region. Bean's Model was used to explain the dynamic magnetic properties peak temperature,Tp and intergrain critical current density, Jc. The most important information from this work is about effect of Bi, Te, Cd, Nb and B substitution at Tl3+ and Ca2+ site on the superconducting fluctuation behaviour and coherence length.,Certification of Masters/Doctoral Thesis is not available,Ph.D.
Pages:	140
Call Number:	QC611.95.F337 2018 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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