Vol.3, No.6, 484-487 (2011) Natural Science
Copyright © 2011 SciRes. OPEN ACCESS
Mechanical and superconducting properties of nanosize
MgO added dip-coated Bi2Sr2CaCu2O8 superconducting
Nasri A. Hamid*, Mohd Yusri Abd Rahman, Noor Fairuz Shamsudin
Department of Engineering Sciences & Mathematics, College of Engineering, Universiti Tenaga Nasional, Kajang, Selangor, Malay-
sia; *corresponding author: nasri@uniten.edu.my
Received 2 February 2011; revised 10 March 2011; accepted 20 March 2011.
In this work, 3% to 8% (in weight) of nanosize
MgO particles was added to Bi2Sr2CaCu2O8 (Bi-
2212) high-temperature superconductor to fab-
ricate Bi-2212 superconducting material with
superior mechanical properties. The mechanical
strength of the samples was studied by con-
ducting the compression test at room tempera-
ture, and the addition of 5% nanosize MgO par-
ticles produced the highest strength when com-
pared with other samples. The sample with 5%
MgO addition also exhibited superior super-
conducting properties. The Bi-2212 powder with
5% nanosize MgO addition was used to fabricate
Bi-2212 tapes through the dip-coating-then-
stacking method. The fully processed tapes
were investigated via dc electrical resistance
measurements, XRD patterns, SEM micrographs,
transport critical current density and tensile
tests. The tensile tests were conducted at room
and cryogenic (77 K) temperatures. Results of
tensile tests and Young’s modulus for the tapes
showed that the Bi-2212 tapes with nanosize
MgO addition recorded better mechanical prop-
erty compared to the non-added samples both at
room and cryogenic temperatures. The double-
core tape with 5% MgO addition recorded the
highest failure point at 160 MPa. In addition to
the strengthening effect that was observed in
the nanosize MgO added Bi-2212 superconduc-
tor tapes, the superconducting properties re-
mained intact in the tapes.
Keywords: Bi-2212 Superconductor; Electrical
Properties; Mechanical Properties; High Current
Density; Cryogenic Temperature
For practical applications of high-temperature super-
conductor materials in power engineering, where ther-
mo-mechanical and electromagnetically induced stresses
are expected to occur, the high-temperature supercon-
ductor materials need to have excellent superconducting
properties and higher mechanical strength. Bismuth
based high-temperature superconductors such as
Bi2Sr2CaCu2O8 (Bi-2212) is one of the most promising
materials due to its high critical current density, rapid
phase formation and phase stability. Nevertheless the
Bi-2212 superconductor, like other Bi-based high-tem-
perature superconductors is generally has poor me-
chanical properties such as low stiffness, strength and
toughness despite their excellent superconducting prop-
erties [1-4]. Low strength and low irreversible strain are
among the factors that hindered the application of
Bi-2212 superconductor in power industry. MgO fibers
have been used to reinforce Bi-2212 superconductor and
are able to improve the mechanical properties of the
compounds [4,5]. Furthermore, the addition of nanosize
MgO particles has shown to be an effective pinning cen-
ter for Bi-2212/MgO compounds and samples with na-
nocrystalline microstructures are found to exhibit better
plasticity under stress compared with samples of larger
grains [6-10].
In the literature, there is no specific report that focuses
on the mechanical strength of single-core and double-
core dip-coated Bi-2212 superconducting tapes with
nanosize MgO addition both at room and cryogenic
temperatures. In the present work, we report our study
on the mechanical and superconducting properties of
such tapes at room and cryogenic temperatures and the
data from this study is important in assessing the per-
formance of the tapes especially at cryogenic tempera-
ture. Throughout this study, the tapes were fabricated
using the dip-coating-then-stacking (DIS) method [11].
N. A. Hamid et al. / Natural Science 3 (2011) 484-487
Copyright © 2011 SciRes. OPEN ACCESS
The Bi2Sr2CaCu2O8 (Bi-2212) with nanosize MgO
addition tapes were prepared through the DIS method.
The silver foil that was used in the fabrication of the
tapes was product of Alfa Aesar with 0.1 mm in thick-
ness and 99.998% purity. In the process, slurry with an
optimum composition was prepared before employing
the dip-coated process. In preparation of the slurry, or-
ganic solution comprises of Span 85 or sorbitane tri-
oleate (C60H108O8), 1,3-propandiol (C3H8O2), polyvinyl
butyral and trichloroethylen (C2HCl3) were used. The
Bi-2212 powder (with and without nanosize MgO addi-
tion) was then added with the solution in the ratio as
shown in Table 1.
The slurry was stirred for 24 hours to obtain a homo-
geneous solution before coating. The coated tape was
then heated at temperature of 80˚C for 48 hours to re-
move any oxide layers before further heating at 500˚C in
flowing oxygen for one hour to remove the organic ma-
terials. After heating, the tape was stacked and conse-
quently rolled to increase the packing density of the ox-
ide core before it is subjected to partial melt process.
During the heat treatment process, the samples were
heated up from room temperature for 2.88 hours until it
reached the partial melt temperature at 865˚C. The tem-
perature was hold for 6 minutes and then cooled down
from 865˚C to 830˚C in 3.5 hours. They were annealed
at 830˚C for 48 hours and then cooled down to room
temperature in 2.77 hours. Partial melt process was em-
ployed to overcome the problem of weak-link within the
Bi-2212 superconducting grains.
The fully processed tapes were characterized through
dc electrical resistance measurements, XRD patterns,
SEM micrographs, and transport critical current density,
Jc. In the dc electrical resistance measurements, Tc, onset
corresponds to the transition onset temperature which is
the point on the R(T) curve where the resistance starts
decreasing dramatically, and Tc, zero corresponds to tran-
sition zero temperature where the resistance is zero. The
XRD patterns were recorded on a Siemen D5000 dif-
fractometer using Cu K radiation. The SEM analysis of
the longitudinal and broad-face cross sectional of the
tapes were conducted using the Philips XL30 environ-
mental scanning electron microscope with EDX analysis.
The transport critical current (Ic) of short samples was
Table 1. Formulation of slurry used to fabricate dip-coated
Component Material Fractions (Weight %)
Oxide powder Bi-2212/ nanosize MgO 22
Solvent Trichloroethylene 68
Binder Polyvinyl butyral 6
spersant Sorbitant triolate 4
measured in a cryostat at 77 K and zero electric field
using the four-probe method with a 1 V/cm criterion.
The transport critical current density (Jc) was calculated
by dividing Ic with the cross-sectional area of the super-
conducting core. The mechanical properties of the tapes
were studied using tensile tests that were conducted at
room and cryogenic (77 K) temperatures. The tests were
conducted using the Instron Material Testing System
model 5567. The slope of the stress-strain curve in the
elastic region represents the stiffness of the material. In a
tensile test, a sample is extended at a constant rate and
the maximum load is measured. The Young’s modulus
was estimated from the linear part of the stress-strain
Figure 1 shows a typical resistivity curve of the tape
samples. The curve shows a metallic behavior due to the
silver tape until the onset temperature where the resis-
tance propitiously dropped to zero. The sharp drop of the
curve indicates high purity of Bi-2212 phase in the su-
perconducting core of the tape.
From our observation, the XRD patterns for both the
non-added and nanosize MgO added Bi-2212 tapes show
a well defined peaks all of which could be indexed on
the basis of a Bi-2212 structure. The (115) peak, which
is the characteristic of the Bi-2212 phase, can be ob-
served clearly in all the samples. Patterns of the nanosize
MgO added tape samples show a more distinct and sharp
Bi-2212 phase peaks, indicating a highly crystalline and
well textured microstructure. A few peaks which corre-
spond to secondary phases such as Bi-2201 phase and
other impurities could also be observed. Those unidenti-
fied peaks are probably due to inappropriate heat treat-
ment during the sintering process which resulted in uni-
Temperature (K)
50100 150 200 250 300
R(T)/R(293 K)
0% MgO
5% MgO
Figure 1. Temperature dependence of resistance of dip-coated
Bi-2212 superconducting tapes (with and without nanosize
MgO addition).
N. A. Hamid et al. / Natural Science 3 (2011) 484-487
Copyright © 2011 SciRes. OPEN ACCESS
dentified secondary phases.
Figure 2 shows a typical SEM micrograph of the
longitudinal cross-sectional of the dip-coated Bi-2212
superconducting tape with nanosize MgO addition. The
micrograph exhibits a well aligned microstructure of the
Bi-2212 superconducting core with closely connected
grain boundaries.
Table 2 shows the critical current density, Jc, zero
transition temperature, Tc zero and onset transition tem-
perature, Tc onset of the tapes. For both the single-core and
double-core tapes, there is enhancement in the Jc after
addition of nanosize MgO. From the observation of
XRD patterns and SEM micrograph, the enhancement is
most likely due to better texturing and well connected
grain boundaries of the superconducting core. The Jc of
the tapes is very much dependent on microstructural
features such as phase purity, grain alignment and grain
Mechanical properties such as stiffness, strength and
toughness are important parameters to indicate the ver-
satility of superconducting tapes [12,13]. Those proper-
ties at room temperature are able to predict such behav-
iors at cryogenic temperature. Figure 3 shows a typical
stress-strain curve for a double-core dip-coated Bi-2212
superconducting tape with nanosize MgO added both at
room and cryogenic temperatures. The non-linear curve
at the initial load is due to low rigidity in which the tape
Figure 2. Typical SEM micrograph of the longitudinal cross-
sectional of the dip-coated Bi-2212 superconducting tape.
Table 2. The critical current density, Jc and transition tempera-
ture, Tc of the dip-coated Bi-2212 superconducting tape.
Nanosize MgO Addition Jc (A/cm2) ± 10 Tc zero (K) Tc onset (K)
0% (single-core) 1800 94 101
5% (single-core) 2400 82 95
0% (double-core) 1900 82 88
5% (double-core) 2300 89 98
0 1 2
Stress (MPa)
273 K77 K
Figure 3. The stress-strain curve for a double-core dip-coated
Bi-2212 superconducting tape with nanosize MgO addition at
room temperature () and 77 K ().
sample was not completely attached to the tester. As the
load increases, a more linear relationship is observed
until deformation and eventually to the failure point.
From our results, a more distinct linear curve was ob-
served in the MgO added samples before deformation
both at room and cryogenic temperatures. The presence
of MgO particles resulted in different mechanical be-
havior between the MgO added and non-added tapes.
Table 3 shows the tensile test measurements for the
single-core and double-core tapes both at cryogenic and
room temperatures. At cryogenic temperature, all the
tapes exhibit higher strength when compared to room
temperature. The double-core tape added with nanosize
MgO recorded the highest strength at about 160 MPa. In
addition, the Young’s modulus for each tape can be es-
timated based on the linear part of each curve. In con-
trast to the tapes’ strength, the Young’s modulus of the
MgO added tape slightly decreased at cryogenic tem-
perature. This is mostly due to lower stiffness of the tape
initiated by microcracks that developed between the
MgO particles and the Bi-2212 superconductor matrix
during cooling to cryogenic temperature [14]. Neverthe-
less, the Young’s modulus is still higher compared to the
non-added tape sample. As such, the Bi-2212 supercon-
ducting tapes with nanosize MgO addition show better
resilience at cryogenic temperature.
Table 3. The tensile test results for double-core and single-core
tapes both at room and cryogenic temperatures.
Nanosize MgO
Max. Strength
at 77 K
(MPa) ± 0.01
Max. Strength at
Room Tempera-
ture (MPa) ± 0.01
0% (single-core) 144.91 117.59
5% (single-core) 146.22 144.83
0% (double-core) 151.01 116.65
5% (double-core) 159.81 146.68
N. A. Hamid et al. / Natural Science 3 (2011) 484-487
Copyright © 2011 SciRes. OPEN ACCESS
We have successfully fabricated nanosize MgO added
Ag-sheathed Bi-2212 superconducting tapes using the
dip-coating-then-stacking (DIS) method. The samples
were subjected to a combination of partial melt and slow
cooling during heat treatment and annealing processes.
The addition of nanosize MgO in both single-core and
double-core tape samples enhanced the Jc and this was
attributed to the presence of MgO that acted as pinning
centers. The double-core tape with 5% nanosize MgO
addition recorded the highest strength. As such, the ad-
dition of nanosize MgO contributed to the improvement
of the mechanical properties of the tapes without de-
grading their superconducting properties.
This project is supported by the Ministry of Science, Technology
and Innovation, Malaysia through eScience fund project no.
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