J Supercond Nov Magn (2013) 26:979–983
DOI 10.1007/s10948-012-2043-x
ORIGINAL PAPER
The Effect of Eu Substitution onto Ca Site in Bi(Pb)-2223
Superconductor Via Co-precipitation Method
J.S. Hawa · H. Azhan · S.Y. Yahya · K. Azman ·
H.N. Hidayah · A.W. Norazidah
Received: 5 November 2012 / Accepted: 3 December 2012 / Published online: 30 December 2012
© Springer Science+Business Media New York 2012
Abstract The samples with nominal composition of Bi
16
Pb
0.4
Sr
2
Ca
2−x
Eu
x
Cu
3
O
y
where x = 0.000, 0.025, 0.050,
0.100, and 0.200 prepared by co-precipitation method
(COP) have been investigated. They were characterized by
X-ray diffraction (XRD), field-emission scanning electron
microscopy (FESEM), electrical and resistivity measure-
ment using the four-probe method. The temperature depen-
dency on electrical resistance showed the superconducting
behavior for all the samples. The critical current density (J
c
)
and superconductivity transition temperature (T
c zero
) of Eu
substituted were found to be lower than those of the pure
sample. T
c zero
varied between 100 and 73 K towards Eu
concentration with the highest T
c zero
in the Eu substitution
was found at 98 K for x = 0.025 and decreased gradually for
further substitution of Eu corresponding to a small change
in the carrier concentration. J
c
decreased with increasing Eu
substitution, and it was measured to be at 5.7512 A/cm
2
in
the Eu free sample and at 2.1223 A/cm
2
for the x = 0.025
sample at 77 K. XRD analyses showed the decrease of
the volume fraction of Bi-2223/Bi-2212 (%) which were
estimated from 78.13/21.87 for x = 0.000 to 23.18/76.82
for x = 0.200. The crystallographic structure was found to
change slightly from tetragonal to orthorhombic in Eu sub-
stituted samples. The lattice parameter c of the Eu samples
decreased due to the incorporation of Eu
3+
(0.95 Å) with
smaller ionic size at the Ca
2+
(0.99 Å) site. From the SEM
investigation, the grain connectivity became weak and the
J.S. Hawa ( ) · S.Y. Yahya · H.N. Hidayah · A.W. Norazidah
Faculty of Applied Sciences, Universiti Teknologi MARA, 40450
Shah Alam, Selangor, Malaysia
e-mail: sitiawe@yahoo.com
H. Azhan · K. Azman
Faculty of Applied Sciences, Universiti Teknologi MARA
Pahang, 26400 Jengka, Pahang, Malaysia
porosity increased with the increment of Eu concentration,
resulting in the decrease of J
c
.
Keywords Bi-2223 · Eu-substitution · Phase formation ·
Superconductor
1 Introduction
The Bi-2223 phase is conducted in order to obtain n = 3 in
Bi
2
Pb
2
Ca
n−1
Cu
n
O
2n+4+8
series with critical temperature
of 110 K [1]. Many works have been carried out to syn-
thesize a single Bi-2223 phase compound. However, it has
been reported to be a difficult task to synthesize the Bi-2223
phase due to the high complexity of the reaction and the ex-
istence of numerous phases during the Bi-2223 phase forma-
tion. In order to overcome these problems, the wet chemical
method such as the co-precipitation and the sol–gel method
have been used to increase the reactivity of precursor powder
[2, 3]. Various elements have been substituted into Bi-2223
to optimize the hole concentration, introduce pinning center
and enhance the formation of the Bi-2223 phase. It should
be interesting to substitute trivalent ions of RE
3+
with di-
valent ions of Ca
2+
. The Ca
2+
substitution in the Bi(Pb)-
2223 superconducting system by rare-earth element RE
3+
is found to suppress the T
c zero
[4, 5]. The substitution of Pb
in the system favors the Bi-2223 phase and substitution of
Dy stabilizes the Bi-2212 phase [6]. Other reports show that
further addition of Sm in Bi(Pb)-2223 reduces the hole car-
rier concentration and causes a suppression in T
c
[7]. Venu
et al. reported that both T
c
and J
c
of Eu substituted onto
Ca-site in Bi(Pb)-2212 is found to be highly enhanced [8].
This paper discusses the effect of Eu substitution at the Ca
site on Bi(Pb)-2223 superconductor using the COP method.
The structure and transport properties of the samples were