UNIVERSITI PUTRA MALAYSIA THE EFFECT OF CD AND NB ON BI-1212 SYSTEM

Transcription

1 UNIVERSITI PUTRA MALAYSIA THE EFFECT OF CD AND NB ON BI-1212 SYSTEM AZMAN AWANG TEH. FSAS

2 THE EFFECT OF Cd AND Nb ON Bi-1212 SYSTEM BY AZMAN AWANG TEH Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of Master of Science June 2004

3 SPECIALLY DEDICATED TO MY WIFE AND FAMILY

4 Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirements for the degree of Master of Science THE EFFECT OF Cd AND Nb ON Bi-1212 SYSTEM BY AZMAN AWANG TEH June 2004 Chairman: Professor Abdul Halim Shaari, Ph.D. Faculty: Science and Environmental Studies The 1212 phase of Bi-based superconductor by theory has good properties in terms of structure and transition temperature, as it is an adaptation of the Y123 system and the Bi22 12 system. The new Bi1212 system with stoichiometries ( ~ ~ 0. 2 ~ )sr2 ~ 0 (~0.3~~ ~ ~ )~~ and (B~~.~P~~,~~M,)s~~ ( ~ ~. ~ ~ a where ~. ~ M = ) Cd ~ and u Nb, ~. x = ~ 0, ~ 0.05, 0 0.1, ~ 0.15, 0.2,0.25 has been successfully synthesized and characterized by means of X-Ray (powder) diffraction, scanning electron microscope, AC susceptibility and resistivity measurements. For the composition of (B~~,~P~~,~M~)s~~(Y~, the above stated systematic examinations clarified the effect of Cd and Nb on Bi-1212 phase, both as a substitution (0 < x i 0.2) and as an addition (x = 0.25). All samples were prepared using solid-state reaction. These samples underwent sintering process at two different temperatures, which were 960 C and 980 C, for a time duration of 2 hours and 10 hours. Then all the samples underwent heat treatment in flowing argon at 750 C for 10

5 hours. All the samples were orthorhombic with the space group Pmmm except the compounds with composition ( ~ i ~ ~ ~ ( ~ ~ b ~ ~, ~ ~ a ~ ~ d and, ~,) ~ u ~ ~ ) ( ~ i ~ ~ ~ ( ~ ~ b ~ ~, ~, ~ ~ a ~ which. ~ ~ d were ) ~ sintered u ~ ~ ~. at ~ 960 C ~ ) 0 for ~ ~ 2 r, hours ~ were tetragonal with space group P4mmm. The X-ray diffraction pattern showed that all samples were in mixed phase (12 12 and 221 2) with acting as a dominant phase. All as-prepared samples showed non-superconducting properties below 20 K, but after heat treatment in flowing argon, some of them showed superconducting properties with the highest transition temperature of Tc,ze,,=64 K and Tc,,,,et=80 K obtained from Nb-doping sample with x=0.2. The ac susceptibility studies showed that most of the superconducting material exhibited weak grain conductivity. The surface morphology of most of the samples observed from scanning electron microscope showed a layered-slab texture.

6 PERPUSTAKAAN SULTAN AB9UL SAMAD ', ' Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains KESAN-KESAN PENDOPAN ELEMEN KE ATAS SISTEM Bi-1212 Oleh AZMAN AWANG TEH Jun 2004 Pengerusi: Profesor Abdul Halim Shaari, Ph.D. Fakulti: Sains dan Pengajian Alam Sekitar Fasa bagi superkonduktor berasakan Bi secara teorinya mempunyai sifat yang baik daripada segi suhu peralihan dan sifat pepejal sampel disebabkan oleh pengabungan antara dua asas iaitu sistem Y 123 dan sistem Bi2212. Sistem Bi1212 yang baru melibat komposisi ( ~ ~ 0. 2 ~ )sr2 ~ (~0.3~~ ~ ~ )~~ dan ( B ~ ~. ~ )sr2 P ~ ( Y ~. ~ ~. ~ c M ~ ~ ~. dengan ~ ) c M u ~ ialah. ~ Cd ~ dan ~ ~ Nb, dengan nilai x=o, 0.05, 0.1, 0.1 5, 0.2, Semua sampel disediakan dengan menggunakan kaedah tindakbalas keadaan pepejal. Sampel-sampel ini disinter pada dua suhu berlainan iaitu 960 C dan 980 C untuk jangkamasa 2 jam dan 10 jam. Sifat angkutan sampel-sampel ini ditentukan dengan menggunakan kaedah penduga empat titik, sifat magnet menggunakan kerentanan au, mikrostruktur oleh Mikroskop Irnbasan Elektron (SEM) dan struktur serta fasa kimia oleh teknik pembelauan sinar-x (XRD). Bagi komposisi ( B ~ ~. ~ P )sr2 ~ ( ~ Y~.~C~~.~)CU. ~ M 2.05~6, pemeriksaan-pemeriksaan yang dinyatakan di atas akan dapat menerangkan kesan Cd dan Nb ke atas fasa Bi1212 sama

7 ada sebagai pendopan (0 < x 5 0.2) atau penambahan (x = 0.25). Terdapat sampel yang bukan superconductor dan sampel yang superkonduktor dengan suhu peralihan yang tertinggi diperolehi adalah Tc,sifar=64 K and Tc,,,1,=80 K daripada sampel pendopan dengan Nb bagi x=0.2. Struktur permukaan semua sampel yang diperolehi daripada ujian SEM menunjukkan permukaan yang berlapis-lapis. Daripada ujian XRD pula didapati struktur bagi semua sampel adalah ortorombik dengan kumpulan Pmmm kecuali sampel dengan komposisi (~i0.2~b0.6~d0.05 )sr2 (~0.3ca0.7 b2.osoe dan ( B ~ ~ ~ ~ P ~ ~ ~ ~ ~ yang c disinter ~ ~ pada ~ ~ suhu ~ 960 C ) s selama ~ ~ 2 ( Y ~ ~ jam adalah tetragonal dengan kumpulan P4mmm. Semua sampel menunjukkan terdapatnya campuran fasa (1212 dan 2212) yang didominasi oleh fasa Kajian kerentanan au ke atas sampel-sampel menunjukkan pengaliran arus di antara butiran- butiran adalah lemah.

8 ACKNOWLEDGEMENTS First of all, I am very grateful to Allah Subhanahu Taala the most beneficent and merciful, for giving me full strength to complete this thesis. I express my deep sense of gratitude to my chairman Prof. Abdul Halim Shaari who has developed my scientific career. I thank him for his invaluable guidance throughout the project by his constant encouragement, constructive suggestions and a series of continuous discussions. I also express my gratitude to my co-supervisors Zainul Abidin Hassan and Associate Prof. Ahmad Kamal Hayati Yahya for their comments, suggestions and guidance throughout my research work. I am very much grateful for the financial assistance provided by the National Science Fellowships (NSF) and the Ministry of Science, Technology and Environment, Malaysia (MOSTE). My special thanks to Miss Nordina and all staff of MOSTE for their kind help throughout my project. My special thanks also go to Mr. Rafi, Miss Aini, Mr. Ho and Miss Azilah for their help in SEM examination, and Mr. Razak Harun for his technical help. I am thankful to my friends Kabashi, Dr. Imad, Dr. Lim, Abdul Samad, Ms Chin Chiu Jin and every one that have lent their help and support to me morally in completing the thesis. vii

9 I certify that an Examination Committee met on 4th June 2004 to conduct the final examination of Azman Awang Teh on his Master of Science thesis entitled "The Effect of Cd and Nb on Bi-1212 System" in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows: Mahdi Abd. Wahab, Ph.D. Faculty of Science and Environmental Studies Universiti Putra Malaysia (Chairman) Sidek Hj. Abdul Aziz, Ph.D. Associate Professor Faculty of Science and Environmental Studies Universiti Putra Malaysia (Member) Zaidan Abd. Wahab, Ph.D. Associate Professor Faculty of Science and Environmental Studies Universiti Putra Malaysia (Member) Roslan Ab. Shukor, Ph.D. Professor Faculty of Science and Technology Universiti Kebangsaan Malaysia (Independent Examiner) School of Graduate Studies Universiti Putra Malaysia Date: 2 6 AUG 2004

10 This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfillment of the requirement for the degree of Master of Science. The members of the Supervisory Committee are as follows: Abdul Halim Shaari, Ph.D. Professor Faculty of Science and Environmental Studies Universiti Putra Malaysia (Chairman) Zainul Abidin Hassan, Ph.D. Faculty of Science and Environmental Studies Universiti Putra Malaysia (Member) Ahmad Kamal Hayati Yahya, Ph.D. Associate Professor Faculty of Applied Sciences Universiti Teknologi Malaysia (Member) AINI IDERIS, Ph.D. Professor/Dean School of Graduate Studies Universiti Putra Malaysia Date: 10 SEP 2004

11 DECLARATION I hereby declare that this thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions. AZMAN AWANG TEH Date: 23 August 2004

12 TABLE OF CONTENTS DEDICATION ABSTRACT ABSTRAK ACKNOWLEDGEMENTS APPROVAL DECLARATION LIST OF TABLES LIST OF FIGURES LIST OF PLATES LIST OF SYMBOLS AND ABBREVIATIONS Page v vii... Vlll X xiii xvii xxviii XXX CHAPTER INTRODUCTION THEORIES ABOUT SUPERCONDUCTORS Type I and Type I1 superconductors Flux pinning Meissner-Ochsenfeld effect BCS theory Bean's model Critical current density: AC determination LITERATURE REVIEW The effect of sintering timeltemperature The effect of annealing process METHODOLOGY Introduction Chemical stoichiometry of Bi-1212 Fabrication of (Bi,Pb,X) superconductor Mixing the Chemicals Calcination Sintering Standard characterization of (Bi,Pb) superconductors Resistance measurement AC susceptibility measurement X-ray Diffraction Microstructure analysis

13 RESULTS AND DISCUSSION X-ray diffraction analysis ( ~ ~ 0. 2 ~ )Sr2(ca~.3y~.7 ~ 0. 6 ~ )Cu2.05~6 ~ ~ ( ~ ~ 0. 4 ~ ~ )Sr2 0 (. ~~O.3~ ~ ~ )Cu2.~506 ~ ( ~ ~ 0. 2 ~ )Sr2(ca0.3y0.7 ~ 0. 6 ~ )cu ~ ( ~ ~ 0. 4 ~ ~ )Sr2 0 (. ~~0.3~ ~ ~ )Cu2.05~6 Microstructure analysis ( ~ ~ 0. 2 ~ )Sr2 ~ ( 0 ~~0.3~ ~ )Cu2.05~6 ~ ~ (Bi~.4pb~.35cdx)Sr2(ca~.3y~.7)Cu2.05~6 ( ~ ~ 0. 2 ~ )Sr2 ~ ( 0 ~~0.3~ ~ ~ )Cu2.05~6 ( ~ ~ 0. 4 ~ ~ br2 0 (~~0.3~ ~ ~ )C~2.05~6 ~ Resistance measurement (Bi~.~pb~.6cdx )Sr2 ( ~~0.3~0.7 b ( ~ ~ o. 4 ~ ~ )Sr2 0 (. ~~0.3~ ~ ~ k~ ~ sam~les ( ~ ~ o. 2 ~ )Sr2 ~ ( 0 ~~O.3~ ~ k~ ~ ( ~ ~ 0. 4 ~ )Sr2 ~ ( o ~~0.3~0.7. i ~ )Cu2.05~6 ~ ~ AC Susceptibility studies (~io.z~bo.6cd~ )Sr2 (ca0.3~0.7)cu2.050a ( ~ ~ 0. 2 ~ )Sr2 ~ ( 0 ~~0.3~ ~ )Cu2.O5~6 ~ samples (~i0.4pb0.35% )Sr2 (cao.3~0.7 )~u samples CONCLUSION AND SUGGESTIONS FOR FUTURE WORK 237 Conclusions 237 ( ~ ~ 0. 2 ~ )Sr2(ca0.3~0.7 ~ 0. 6 ~ ~ )C"2.05~6 ~ 239 ( ~ ~ 0. 4 ~ ~ )Sr2 0.( ~~0.3~ ~ ~ b ~ samples 241 ( ~ ~ 0. 2 ~ )Sr2 ~ ( 0 ~~0.3~ ~ ~ )C"2.05~6 ~ 242 ( ~ ~ 0. 4 ~ ~ )Sr2 0 (. ~~0.3~ ~ ~ b ~ Samples 243 Suggestions For Future Work 245 REFERENCES APPENDICES BIODATA OF THE AUTHOR xii

14 LIST OF TABLES Table 1.1 Low-Temperature Superconductors [3]. 1.2 High-Temperature Superconducting Compounds [5]. Page Temperaturehime schedule for sintering and annealing process of material from the system (~i, (Y, ~ a ) C u ~., ~ ~ 0 ~ Pb, M )s~~ Lattice parameters and volume fraction of phase of (~i~,~~b~&d, 81-2 ( c ~ ~.)CU~.~~O~ ~ Y ~. ~ samples sintered at 960'~ Lattice parameters and volume fraction of 1212 phase of ( ~ i ~. ~ )Sr2(~a0,3~0.7)~~2.05~6 ~ b ~, ~ ~ d ~ samples sintered at 960'~ Lattice parameters and volume fraction of phase of (~io.2pb 0.6~d,)sr2 )CU 2.05~6 samples sintered at 980'~ Lattice parameters and volume fraction of 1212 phase of ( ~ i ~, ~ ~ )sr2 b ~. ~ ~ d, 2,05~g samples sintered at 980'~ Lattice parameters and volume fraction of phase of (~i0.4pb o.3s~dx )Sr2( c ~ ~.)Cu ~ Y 2.05~s ~. ~ samples sintered at 960'~ Lattice parameters and volume fraction of 212 phase of ( ~ i ~, ~ )Sr2 ~ ( b c ~ ~., ~ )CU ~ ~ Y 2.05~S ~. d ~ samples sintered at 960'~ Lattice parameters and volume fraction of phase of ( ~ i ~ 0.35cd. ~ ~ )Sr2 b ( c ~ ~. )Cu ~ Y 2.05~6 ~, ~ samples sintered at 980'~ Lattice parameters and volume fraction of 1212 phase of ( ~ i ~. ~ )Sr2 ~ ( c b ~ ~ ~,.)CU~.~~O~ ~ Y ~ ~ ~. ~ samples d ~ sintered at 980'~ Xlll

15 5.1.9 Lattice parameters and volume fraction of 1212 phase of ( ~ i ~ ~ ~ ~ b ~ )Cu2,05~g ~ ~ N samples b ~ ) sintered ~ r at ~ 960'~ ( ~ a ~ ~ ~ ~ ~ ~ Lattice parameters and volume fraction of phase of ( B ~ ~ ~ ~ P ~ ~ )CU~.~~O~ ~ ~ N samples ~ ~ ) sintered s ~ at 960'~ ~ ( c ~ ~ ~ ~ Y ~ Lattice parameters and volume fraction of phase o f ( ~ i ~ ~ ~ ~ b ~ ~ ~ N b samples ~ ) sintered ~ r ~ at ( 980'~ ~ a ~ ~ ~ ~ ~ ~ ~ ) Lattice parameters and volume fraction of phase of ( ~ i ~. ~ ~ )sr2 b ~ (. c ~ ~ N~ b.)cu ~ Y 2.05~g ~. ~ samples sintered at 980'~ Lattice parameters and volume fraction of phase of (Bi0,4Pb 0.35Nbx )sr2( c ~ ~.)Cu ~ Y 2.05~g ~. ~ samples sintered at 960'~ Lattice parameters and volume fraction of phase of )Sr2( c ~ ~.)Cu ~ Y 2.05~6 ~. ~ samples sintered at 960'~ Lattice parameters and volume fraction of 1212 phase of ( ~ i ~. ~ ~ b )Sr2 ~.( ~ c ~ N~ b,)cu~,~~o~ ~, Y ~. samples ~ sintered at 980'~ Lattice parameters and volume fraction of phase of ( ~ i ~ NbX. ~ )Sr2 ~ ( b c ~ ~.. ~ ~ ~ Y ~. ~ samples sintered at 980'~ Values of Tc,,.+ and Tc, on,,, of the superconducting samples )Sr 2 ( c ~ ~.)Cu2.05~6 ~ Y ~, of ~ different x composition, sintered at 960 C Values of T,,,o and Tc,, of the superconducting samples )~r 2 ( c ~ ~, ~ Y ~. of ~ different x )cu~.~~o~ composition, sintered at 960 C Values of Tc, 4 and Tc,,, of the superconducting samples ( ~ i ~. ~ )Sr ~ 2 ( b c ~ ~.. ~ ~ ~ Y d ~. ~ of ~ different x )CU~.~~O~ composition, sintered at 980 C xiv

16 Values of Tc, o, and Tc, onset of the superconducting samples (~i~.~~b~&d, )Sr 2 ( c ~ ~. ~ Y ~. ~ of different x )CU~.~~O~ composition, sintered at 980 C Values of Tc, o, and Tc, onset of the superconducting samples ( ~ i ~. ~ )ST ~ 2(~a0.3~0.7 b ~. )CU~.~~O~ ~ ~ ~ of d different ~ x composition, sintered at 960 C Values of Tc, o, and Tc, on,et of the superconducting samples ( ~ i ~. ~ )Sr ~ 2(~a0.3~0.7 b ~. )CU~.~~O~ ~ ~ ~ of d different ~ x composition, sintered at 960 C Values of Tc, o, and Tc, onset of the superconducting samples ( ~ i ~. ~ )Sr ~ 2(~ao.3~o.7 b ~. ~ ~ ~ of d different ~ x ) C U ~. ~ ~ ~ ~ composition, sintered at 980 C Values of Tc, o, and Tc, on,et of the superconducting samples ( ~ i ~. ~ )Sr ~ 2(~a0,3~0.7 b ~. ~ ~ ~ of d different ~ x )CU~,~~O~ composition, sintered at 980 C Values of Tc, o, and Tc, onset of the superconducting samples (~i~.~~b~.~nb, )Sr 2 ( c ~ ~.)Cu2.05~g ~ Y ~. ~ of different x composition, sintered at 960 C Values of Tc, o, and Tc, of the superconducting samples (~i~.~~b~.~nb, )Sr 2 ( c ~ ~.)Cu2.05~6 ~ Y ~. of ~ different x composition, sintered at 960 C Values of Tc, and Tc,,,,, of the superconducting samples ( ~ i ~. ~ ~ b ~ 2 (. c ~ ~ ~ b., ) ~ ~ Y r ~. of ~ different ) c u ~ x. ~ ~ ~ ~ composition, sintered at 980 C Values of Tc, o, and Tc, of the superconducting samples ( ~ i ~. ~ ~ b ~. ~ N b ~ of different x )Sr 2 ( c~~~y~,~)c~~,~~o~ composition, sintered at 980 C Values of Tc, o, and T,, onset of the superconducting samples )Sr 2 ( c ~ ~. ~ Y ~. ~ of different x composition, sintered at 960 C

17 Values of T,,,o and T,, onset of the superconducting samples ( ~ ~ 0. 4 ~ ~ br 02.( ~~0.3~ ~ ~ k~ different composition, sintered at 960 C Values of Tc,,o and Tc, of the superconducting samples ( ~ i ~. ~ ~ )Sr b 2 ( ~ ~. a ~ ~. ~ ~ b ~, ~ of different. ~ ) x ~ u ~. ~ ~ 0 ~ composition, sintered at 980 C Values of T,,,o, T,, on,et of the superconducting samples )Sr ~ (c~o.~yo.~ ( ~ ~ 0. 4 ~ ~ ~ ~ )C~2.0.5~6 ~ different composition, sintered at 980 C A.111 Lattice parameters of ( ~i~.~~b~&d,)~r~ ( c ~ ~.)Cu ~ Y 2,05~6 ~. ~ samples sintered at 980'~ for 2 hours. xvi

18 LIST OF FIGURES Figure Page The resistance of mercury drops at about 4.2 K [I]. 1 Comparison between superconductors with perfect diamagnetism and infinite conductivity [2]. Chronological discovery of some of important superconducting materials [5]. Crystalline structure of Bi1212 material where M is the cation doping [7,12]. Magnetization versus applied magnetic field for type I superconductor [2]. Schematic phase diagram illustrating normal and superconducting regions of type I superconductor [2] Magnetization versus applied magnetic field for a type I1 superconductor [2]. Schematic phase diagram illustrating normal, mixed and Meissner regions of type I1 superconductor. <B> denote the average magnetic field in the mixed state of the superconductor [2]. A lattice distortion due to the moving electron. As a negatively charged electron passes through between positively charged ions in the lattice, the ions are attracted inward. This distortion of the lattice creates a region of enhanced positively charge (phonons) which attracts another electron to the area [29]. Formation of Cooper pairs. The two electrons are locked together resulting from virtual exchange of phonons will travel through the lattice [29]. Flow chart for fabrication of (Bi,Pb) and doped superconductors. Graph of Temperature versus Time for sintering process. Graph of Temperature versus Time for annealing process. xvii

19 4.4 Schematic diagram of four point probe resistance device. 4.5 Illustrates schematically how the principles of AC susceptometry [59]. 4.6 Cross-section view of the coil assembly [59]. 4.7 An experiment arrangement used in an AC Susceptometer. Note the sample moment varies with time in an AC measurement [59]. )CU~.~~O~ XRD pattems of ( ~ i ~. ~ )Sr2(~a0.3~0.7 ~ b ~. ~ ~ d ~ samples sintered at 960'~ Cell parameters versus x composition of ( ~ i ~. ~ )Sr2 ~ ( b c ~ ~.,)Cu2.050S ~ Y ~ ~ d. samples ~ sintered at 960'~ Percentage of volume fraction of 1212 versus x composition of ( ~ i ~. ~ )Sr2 ~ ( b c ~ ~.,)CU~.~~O~ ~ Y ~ ~ d. samples ~ sintered at 960'~ )cu~.~~o~ XW) patterns of ( ~ i ~. ~ )Sr2 ~ ( b c ~ ~.. ~ Y ~ ~ d. ~ samples sintered at 960'~ Cell parameters versus composition x of ( ~ i ~. ~ )Sr2 ~ ( b c ~ ~.,) ~ CY ~ U ~ d. ~ samples ~. ~ ~ sintered ~ ~ at 960'~ Percentage of volume fraction of 1212 versus x composition of ( ~ i ~. ~ )Sr2 ~ ( b c ~ ~.. ~ Y ~ ~ d. ~ samples ) c ~ sintered ~. ~ ~ at o 960'~ ~ XRD pattems of samples ( ~ i ~. ~ ~ b ~ (, c ~ ~ ~ ~ d )CU~,~~O~,, ) ~ ~ Y r ~ ~ x = 0,0.05, 0.1, 0.15, 0.2 and 0.25 sintered at 980'~ for 2 hours and annealed Cell parameters versus x composition of ( ~ i ~. ~ )Sr2 ~ ( b c ~ ~.,)CU~,~~O~ ~ Y ~ ~ d. samples ~ sintered at 980'~ Percentage of volume fraction of 1212 versus x composition of )Sr2( c ~ ~. ~ Y ~, samples ~ sintered at 980'~ )CU~,~~O~ xviii

20 5.110 XRD patterns of ( ~ i ~. ~ ~ )Sr2(~a0,3~0,7 b ~ & d ~ sintered at 980'~ ) C U ~ samples. ~ ~ ~ ~ Cell parameters versus x composition of ( ~ i ~. ~ )Sr2 ~ ( b c ~ ~..)CU~.~~O~ ~ Y ~ ~ d. ~ samples sintered at 980'~ Percentage of volume fraction of 1212 versus x composition of ( ~ i ~ ~ P b )sr2 ~ (. ~ c ~ d ~,)CU~,~~O~. ~ Y ~ samples ~ sintered at 980'~ XRD patterns of ( ~ i ~. ~ )Sr2 ~ ( c b ~ ~ ~.)CU~.~~O~ ~ Y ~ ~ ~. ~ d ~ samples sintered at 960'~ 5.1.I4 Percentage of volume fraction of 1212 versus x composition of (Bio.4Pb o.35~dx )Sr2( c ~ ~.)Cu ~ Y 2.05~6 ~. ~ samples sintered at 960'~ Cell parameters versus composition x of ( ~ i ~, ~ )Sr2 ~ (cag3yg7 b ~.) CU~.~~O~ ~ ~ ~ samples d ~ sintered at 960'~ XRD patterns of ( ~ i ~ ~ )Sr2 ~ ( c ~ ~ b.)cu2.05~g ~ Y. ~. ~ ~ ~ ~ d ~ samples sintered at 960'~ Cell parameters versus x composition of ( ~ i ~. ~ ~ )Sr2 b ( ~ c. ~ ~ ~.)CU~.~~O~ ~ ~ Y d ~,. ~ samples sintered at 960'~ Percentage of volume fraction of versus x composition of ( ~ i ~. ~ )Sr2(~a0.3~0.7)C~2,0506 ~ b ~. ~ ~ ~ samples d ~ sintered at 960'~ )CU~.~~O~ XRD patterns of ( ~ i ~, ~ )Sr2(~a0.3~0.7 ~ b ~, ~ ~ ~ d ~ samples sintered at 980'~ Cell parameters versus x composition of ( ~ i ~. ~ )Sr2 ~ b ~. )Cu ~ 2.05~a ~ ~ samples d ~ sintered at 980'~ xix

21 Percentage of volume fraction of 1212 versus x composition of (Bi0.4Pb 0.35~d )Sr2(ca 0.3~0.7 )Cu 2,0S~S samples sintered at 980'~ XRD patterns of ( ~ i ~. ~ )Sr2 ~ ( c b ~ ~. )CU ~ ~ Y 2.05~6 ~. ~ ~ samples d ~ sintered at 980'~ Cell parameters versus x composition of ( ~ i ~. ~ )Sr2 ~ ( c b ~ ~,.) ~ CY ~ U ~ ~. ~ samples ~ d. ~ sintered ~ ~ ~ at 980'~ Percentage of volume fraction of 1212 versus x composition of ( ~ i ~. ~ )Sr2 ~ ( c b ~ ~ ~..)Cu2,050g ~ Y ~ ~ ~. samples ~ d ~ sintered at 980'~ )CU~.~~O~ XRD patterns of (~i~,~~b~.~nb,)~r~ ( c ~ ~. ~ Y ~. ~ samples sintered at 960'~ Cell parameters versus x composition of ( ~ i ~. ~ ~ )sr2 b ~ (. c ~ ~ N~ b.)cu~.~~o~ ~ Y ~, samples ~ sintered at 960'~ Percentage of volume fraction of 1212 versus x composition of )srz( c ~ ~.)Cu ~ Y 2.05~6 ~. ~ samples sintered at 960'~ )CU~.~~O~ XRD pattern of ( ~ i ~. ~ ~ ( b c ~ ~. ~ ~ Y b ~ ). samples ~ r ~ sintered at 960'~ Cell parameters versus x composition of ( B ~ ~. ~ P ~ ~ ~ ~ N ~ ~ samples ) s ~ sintered ~ ( at c 960'~ ~ ~ ~ ~ Y ~ ~ ~ ) c Percentage of volume fraction of versus x composition of ( ~ i ~, ~ )l Sr2 ~ ( b c ~ ~.. ~ CY ~ ~ U b. ~ samples ) ~, ~ sintered ~ at ~ 960'~ ~ XRD patterns of ( ~ i ~. ~ ~ b ~ ( c. ~ ~ N. b )Cu2.05~6 ~ ~ Y ) ~ ~. r ~ samples ~ sintered at 980'~ Cell parameters versus x composition of ( ~ i ~. ~ ~ )sr2 b ~ ( c. ~ ~ N. b )Cu ~ ~ Y 2.05~6 ~, samples ~ sintered at 980'~

22 Percentage of volume fraction of 1212 versus x composition of ( ~ i ~. ~ ~,)sr2 b ~ (. c ~ ~ N~ b,)cu~.~~o~ ~ Y ~, samples ~ sintered at 980'~ XRD patterns of (~i~.~~b~.~nb, )sr2 sintered at 980'~ samples Cell parameters versus x composition of ( ~ i ~, ~ )sr2 ~ ( b c ~ ~. ~ )Cu2.05~g ~ NY b ~. ~ ~ samples sintered at 980'~ Percentage of volume fraction of 1212 versus x composition of (~i~.~~b~.~nb, )sr2( c ~ ~.)CU ~ Y 2,05~6 ~, samples ~ sintered at 980'~ XRD patterns of )Sr2(~a0.3~0,7)~u samples sintered at 960'~ Cell parameters versus x composition of (~i~,~pb~.~~nb, )Sr2( c ~ ~,)Cu2,05~S ~ Y ~. samples ~ sintered at 960'~ Percentage of volume fraction of 1212 versus x composition of (~i~.~pb~.~~nb, )SrZ( c ~ ~.)CU~.~~O~ ~ Y ~. ~ samples sintered at 960'~ XRD patterns of )Sr2( c ~ ~.)Cu2.05~6 ~ Y ~, ~ sintered at 960'~ samples Cell parameters versus x composition of )Sr2( c ~ ~. ~ Y ~. samples ~ ) c sintered u ~. ~ at ~ 960'~ ~ ~ Percentage of volume fraction of 1212 versus x composition of (~i~,~pb~.~~nb, )Sr2(~ao,3~o,7 )CU~,~~O~ samples sintered at 960'~ XRD patterns of ( ~i~.~~b~.~~nb,)~r~ sintered at 980'~ (c~~.~y~.~)c~~.~~o~ samples xxi

23 Cell parameters versus x composition of ( ~ i ~. ~ ~ )Sr2 b ( ~ c. ~ ~ ~ ~.) ~ NCY b U ~. ~ samples. ~ sintered ~ ~ ~ at 980'~ Percentage of volume fraction of 1212 versus x composition of ( ~ i ~. ~ ~ )Sr2 b ( ~ c. ~ ~ ~ ~,)CU~.~~O~ ~ N Y b ~. samples ~ sintered at 980'~ )CU~,~~O~ XRD patterns of ( ~ i ~. ~ )Sr2 ~ ( c b ~ ~., ~ ~ Y ~, ~ ~ samples b ~ sintered at 980'~ Cell parameters versus x composition of ( ~ i ~. ~ ~ b )Sr2 ~,( ~ c ~ ~ N~ b )CU~,~~O~., ~ Y ~ samples ~ sintered at 980'~ Percentage of volume fraction of 1212 versus x composition of ( ~ i ~. ~ )Sr2 ~ ( c b ~ ~ ~.)CU~,~~O~ ~ Y ~ ~ ~, ~ samples b ~ sintered at 980'~ 152 ( B ~ ~, ~ P ~ ~ ~ ~ c ~ ~ x ) = 0, S 0.05, ~ ~ 0.1, ( 0.15, C ~ ~, ~ Y ~ ~ ~ ) C 0.2,0.25, sintered at 960 C (~i0,2~bo.&d, )Sr 2(~a0.3~0.7)Cu2.0506, x = 0,0.05,0.1,0.15, 0.2, 0.25, sintered at 960 C Fr 2(~a0.3~0.7)~u2.05~6, x = 0, 0.05, 0.1, 0.15, 0.2,0.25, sintered at 980 C x = 0, 0.05, 0.1, 0.15, (B~~,~P~~,~c~,)S~~(C~~,~Y~,~)C~~,~~O~ 0.2, 0.25, sintered at 980 C (~io.4pb0.35cdx)sr 2(cao.3~0.7 )Cu2.0506, x = 0, 0.05, 0.1, 0.15, 0.2,0.25, sintered at 960 C The normalized resistance versus temperature of samples (~io.4~b 0.3, ~dx)sr2(~a0.3~0.7)cu2.050~, x = 0, 0.05, 0.1, 0.15, 0.2,0.25, sintered at 960 C xxii

24 (~io.4~bo.35~dx)sr2(~a0.3~0.7)c~2.0506, x = 0,0.05, 0.1, 0.15, 0.2,0.25, sintered at 980 C ( ~ ~ 0. 4 ~ ~ )Sr2(~a0.3~ ~ ~ )C~2.0508, ~ x =0, 0-05, 0.1, 0.15, 0.2,0.25, sintered at 980 C ( ~ i ~ ~ ~ ~ b ~ ~ ~ N b ~ ) ~ x = r 0, ~ 0.05, ( ~ 0.1, a 0.15, ~ ~ ~ ~ ~, ~ ) C u ~ ~ 0.2,0.25, sintered at 960 C (~io.2~b0.6~x )Sr2 (~a0.3~0.7)~u2.050g, x = 0,0.05,0.l, 0.15, 0.2,0.25, sintered at 960 C ( B ~ ~, ~ P ~ ~ ~ ~ ~, ) S x = ~ 0, ~ 0.05, ( C 0.1, ~ 0.15, ~, ~ Y ~ ~ ~ ) C ~ ~ 0.2,0.25, sintered at 980 C (~io.2pbo.6mx )Sr2 (~a0.3~0.7)c~2.0506, X = 0,0.05,0.l, 0.15, 0.2,0.25, sintered at 980 C (Bio.4pb0.35mx)Sr2(ca0.3~0.7 )Cu2.0506, x = 0, 0.05,0.1,0.15, 0.2,0.25, sintered at 960 C (~io.4~bo.35~b~ )Sr 2(~a0.3~0.7 )Cu2.0508, x = 0,0.05,0.1,0.15, 0.2,0.25, sintered at 960 C (Bio.4~bo.35mx)Sr 2(cao.3yo.7 )Cu2.0506, x = 0, 0.05, 0.1,0.15, 0.2, 0.25, sintered at 980 C 0.2, 0.25, sintered at 980 C xxiii

25 5.4.1 (a-b) AC susceptibility component (a) it and (b) i of ( B ~ ~ ~ ~ P ~ ~ ~ ~ c ~ ~, x=0.05 ) s ~ sintered ~ ( at Y 980 C ~ ~ ~ c ~ ~, ~ ) c (a-b) AC susceptibility component (a) i' and (b) i of ( ~ i ~. ~ ~ b ~ (. ~ ~ ~ ~. d ~, ) ~ ~ a r, ~ x=0.1. ~ sintered ) ~ at u 980 C ~. ~ ~ 0 ~ 5.4.3(a-b) AC susceptibility component (a) it and (b) i of ( ~ i ~. ~ ~ b ~ (. ~ ~ ~ d, ) ~ ~ r ~, ~ x=o.l5 ~ sintered a ~ at 980 C ~ ~ ) ~ u ~ ~ 5.4.4(a-b) AC susceptibility component (a) < and (b) i of ( B ~ ~ ~ ~ P ~ ~ ~ ~ c, ~ x=0.2, sintered ) s ~ at 980 C ~ ( Y ~ ~ ~ c ~ ~ ~ 5.4.5(a-b) AC susceptibility component (a) i' and (b) i of (B~~~~P~~~~c~,)s~~(Y~~~c~~,~)c~~, x=0.25 sintered at 980 C 5.4.6(a-b) AC susceptibility component (a) < and (b) i of ( B ~ ~ ~ ~ P ~ ~ ~ ~ c ~, x=0.05 ) s sintered ~ ~ ( at 980 C Y ~ ~ ~ c ~ ~ ~ ~ ) 5.4.7(a-b) AC susceptibility component (a) < and (b) of, x=0.15 sintered at 980 C 218 ( B ~ ~ ~ ~ P ~ ~ ~ ~ c ~ ~ ) s ~ ~ ( Y ~ ~ ~ c ~ ~ 5.4.8(a-b) AC susceptibility component (a) and (b) of (B~~,~P~~,~c~,)s~~(Y~,~c~~,~)c~~~~~, x=0.25 sintered at 980 C 5.4.9(a-b) AC susceptibility component (a) and (b) of, x=0.2 sintered at 960 C ( B ~ ~ ~ ~ P ~ ~ ~ ~ N ~ ~ ) s ~ ~ ( Y ~ ~ ~ c ~ ~