The Effect of Cd and Nb on Bi-1212 System
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 (Bi0.2Pb0.6Mx)Sr2(Y0.3Ca0.7)Cu2.05O and ( B ~ ~ . ~ P ~ ~(, ~ ~~M...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/6335/1/FSAS_2004_11.pdf |
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| Summary: | 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
(Bi0.2Pb0.6Mx)Sr2(Y0.3Ca0.7)Cu2.05O and
( B ~ ~ . ~ P ~ ~(, ~ ~~M. ,~) s~~a~ w ~he.re ~M =) C~d anud N~b, .x =~ 0, ~0.005, 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 ~ ) sth~e ~ ( Y ~ , 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 hours. All the samples were orthorhombic with the space group Pmmm except the
compounds with composition ( ~ i ~ ~ ~ (~ ~b~~, ~~ ~ a~ ~dan,d ~~ ,) ~~ u~ ~) ( ~ i ~ ~ ~ (~ ~b~ ~, ~, ~~a ~~w.~hic~hd w)er~e suin~te~re~d. at~~ 96~0)°C0 f~o~r 2r, ho u~rs
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 12 12 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. |
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