Superconducting Order Parameter Fluctuation in Doped and Composite Cuprate Superconductors

By: Mohanta, AnnapurnaContributor(s): Behera, D [Supervisor] | Panigrahi, S [Supervisor] | Department of PhysicsMaterial type: TextTextLanguage: English Publisher: 2011Description: 187 pSubject(s): Physics | Electricity and MagnetismOnline resources: Click here to access online Dissertation note: Thesis (Ph.D)- National Institute of Technology, Rourkela Summary: This thesis describes work in the area of high temperature superconductors. Attempts have been made for the synthesis of doped and composites of YB CO superconductors to study the electrical and magnetic properties. The general objective of this work is to look at the effect of inhomogeneities and secondary phases on Superconducting order parameter fluctuation (SCOPF) in doped and composite superconductors. The influence of inhomogeneities on the microstructural and electrical properties is investigated for the simultaneous incorporation of Ga 3+ and Zn 2+ to the Cu-site of YBa 2 Cu 3 O 7- δ . The evolution of anisotropy has also been analyzed for the effect of both hole doping to the Y- site through Ca, and CuO-chain electronic state anisotropy by Zn doping to the Cu-site through SCOPF analysis. Conductivity fluctuation analysis performed around T c , provides evidence that dimensionality of fluctuations depends on the doping level in the mean field regimes. The inclusion of sub-μ sized BZO particles and nano-BaTiO 3 to the YBCO matrix bring about structural as well as dimensional fluctuation changes in the electrical transport properties. The characteristic scaling of the curves obtained from excess conductivity ( ∆ σ ) as a function of reduced temperature, ε for YBCO + x BaZrO 3 composites (x = 0, 1, 2.5, 5 and 10 wt.%) in 8 T magnetic field showed a crossover between two to three-dimensional (T LD ) behaviors in the mean-field region but the critical region is not witnessed due to smearing out of data points in high magnetic field like 8 T. Study of magneto-resistance and vortex dynamics in YBCO superconductors has been done to get requisite information for properties such as critical current density, quantized flux trapping and activation energy. The activation energy and critical current density associated with magnetic field gives the vital inferences on inter and intra-granular behaviour. The resistive broadening in the tailing region due to application of magnetic field has been explained on the Ambegaokar–Halperin (AH) phase-slip theory. When magnetic field is applied to type-II superconductors magnetic flux can penetrate in the form of Abrikosov vortices flux lines, each carrying a quantum of magnetic flux Ф 0 = e h 2 / . As density of flux lines increases due to application of magnetic field these vortices form flux line lattice (FLL) due to interaction. In order to have a detail understanding of flux pinning mechanism, critical current density studies have also been carried out in YBCO + x BaZrO 3 (BZO) composites. The flux pinning effect of submicron BZO particles in the composites enhances the current density J c from 8 x 10 4 A- cm -2 for pristine YBCO to 2 x 10 5 A-cm -2 for YBCO + 5 wt % BZO composite samples in field varying from 1 – 16 T at a temperature of 40 K.
Tags from this library: No tags from this library for this title. Log in to add tags.
    Average rating: 0.0 (0 votes)
Item type Current location Collection Call number Status Date due Barcode
Thesis (Ph.D/M.Tech R) Thesis (Ph.D/M.Tech R) BP Central Library
Thesis Section
Reference Not for loan T129

Thesis (Ph.D)- National Institute of Technology, Rourkela

This thesis describes work in the area of high temperature superconductors. Attempts have been made
for the synthesis of doped and composites of YB
CO superconductors to study the electrical and
magnetic properties. The general objective of this work is to look at the effect of inhomogeneities and
secondary phases on Superconducting order parameter fluctuation (SCOPF) in doped and composite
superconductors. The influence of inhomogeneities on the microstructural and electrical properties is
investigated for the simultaneous incorporation of Ga
3+
and Zn
2+
to the Cu-site of YBa
2
Cu
3
O
7-
δ
.
The
evolution of anisotropy has also been analyzed for the effect of both hole doping to the Y- site through
Ca, and CuO-chain electronic state anisotropy by Zn doping to the Cu-site through SCOPF analysis.
Conductivity fluctuation analysis performed around T
c
, provides evidence that dimensionality of
fluctuations depends on the doping level in the mean field regimes. The inclusion of sub-μ sized BZO
particles and nano-BaTiO
3
to the YBCO matrix bring about structural as well as dimensional
fluctuation changes in the electrical transport properties. The characteristic scaling of the curves
obtained from excess conductivity (

σ
) as a function of reduced temperature,
ε
for YBCO + x BaZrO
3
composites (x = 0, 1, 2.5, 5 and 10 wt.%) in 8 T magnetic field showed a crossover between two to
three-dimensional (T
LD
) behaviors in the mean-field region but the critical region is not witnessed due
to smearing out of data points in high magnetic field like 8 T.
Study of magneto-resistance and vortex dynamics in YBCO superconductors has been done to get
requisite information for properties such as critical current density, quantized flux trapping and
activation energy. The activation energy and critical current density associated with magnetic field
gives the vital inferences on inter and intra-granular behaviour. The resistive broadening in the tailing
region due to application of magnetic field has been explained on the Ambegaokar–Halperin (AH)
phase-slip theory.
When magnetic field is applied to type-II superconductors magnetic flux can penetrate in the form
of Abrikosov vortices flux lines, each carrying a quantum of magnetic flux
Ф
0
=
e
h
2
/
. As density of
flux lines increases due to application of magnetic field these vortices form flux line lattice (FLL) due
to interaction. In order to have a detail understanding of flux pinning mechanism, critical current
density studies have also been carried out in YBCO +
x
BaZrO
3
(BZO)
composites. The flux pinning
effect of submicron BZO particles in the composites enhances the current density J
c
from 8 x 10
4
A-
cm
-2
for pristine YBCO to 2 x 10
5
A-cm
-2
for YBCO + 5 wt % BZO composite samples in field
varying from 1 – 16 T at a temperature of 40 K.

There are no comments on this title.

to post a comment.

Implemented and Maintained by Biju Patnaik Central Library.
For any Suggestions/Query Contact to library or Email: library@nitrkl.ac.in OR bpcl-cir@nitrkl.ac.in. Ph:91+6612462103
Website/OPAC best viewed in Mozilla Browser in 1366X768 Resolution.

Powered by Koha