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Chapter 5: Introduction
Chapter 5: Intercalation
into High-Temperature Superconductors
The bismuth-based superconductors
with composition of Bi2Sr2Can-1CunO2n+4 are
unique to the class of cuprate materials in that they possess a large
van der Waals gap between adjacent bismuth-oxide layers. This van
der Waals gap is a result of 6s2 lone pairs on bismuth1 that are directed toward the gap. The gap size is about
3.2 Å. Numerous research studies have utilized this gap for the insertion
of a variety of materials such as iodine,2-55 AgI,56-60 HgI2,61-64 lithium,65-71 metal phthalocyanines,72-83 and other organic materials.84-91
The electrical properties
of conducting polymers, such as polypyrrole, can be modified by oxidative
doping of the neutral, insulating polymer to a conductive state and
undoped by a reductive process.92-95 Recently, polymer intercalation has been accomplished96-98 using a variety of nonsuperconducting host lattices such
as zeolites,99-103 FeOCl,104-107 silicates,108-110 and other materials.111 The conductive properties of many of these systems have been
dramatically modified by the inclusion of the conducting polymer in
an insulating material.
The creation of a hybrid
system involving a high-temperature superconductor and a conducting
polymer could be tailored, which involves “tuning” the electrical properties
of the system. In order to construct this hybrid system, the controlled
insertion of the conducting polymer must first be demonstrated. Here,
it is demonstrated that insertion of polypyrrole between the adjacent
Bi-O layers in Bi2Sr2CaCu2O8+x can
be achieved
In this chapter, methods
for intimate assembly of a conductive polymer into the high-temperature
superconductor lattice of a bismuth based cuprate system are described. Here,
polypyrrole is intercalated into I-Bi2Sr2Can-1CunO2n+4. First,
in sections 5.1 - 5.4, a summary of prior relevant intercalation studies
of the Bi2Sr2Can-1CunO2n+4 system
is provided along with background on intercalation of other polymers
into layered structures. Second, in sections 5.5 - 5.6, the new research
on polypyrrole incalated into the Bi2Sr2Can-1CunO2n+4 system
is presented.
