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JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS Vol. 11, No. 10, October 2009, p. 1541 - 1544
BSCCO ceramics doped with ferromagnetic manganite
phases♣
A. STANEVA*, A. STOYANOVA-IVANOVAa, S. TERZIEVAa, J. SHOUMAROVA, K. GRIGOROVb,
A. ZALESKIc, V. MIKLId, CH. ANGELOVe, Y. DIMITRIEV
University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756 Sofia, Bulgaria
a Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784
Sofia, Bulgaria
b Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia, Bulgaria
C Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wroclaw, Poland
d Centre for Materials Research, Tallin Technical University, Ehitajate 5, Tallin 19086, Estonia
e Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd.,
1784 Sofia, Bulgaria
Bulk superconducting BSCCO ceramics involving a manganite phase have been obtained by two different methods: solid
state synthesis and a low temperature sol-gel method. The microstructure of these materials was studied by scanning
electron microscopy (SEM), X-ray diffraction and using the method of energy dispersive spectroscopy (EDX). The results
suggest that the composites reveal superconductivity (at 86.6K). The obtained samples have dense structures which
preserve the La-manganite phase as fine grains on the boundary with Bi phases. This composite is a potential candidate as
a multifunctional material for applications in microelectronics.
(Received November 5, 2008; accepted December 15, 2008)
Keywords: Composites, Ceramic superconductors, BSCCO, Manganites
♣ Paper presented at the International School on Condensed Matter Physics, Varna, Bulgaria, September 2008
1. Introduction
The coexistence of superconductivity and
ferromagnetism has attracted widespread interest
associated with the critical parameters of superconductors.
Maple [1] published a comprehensive review on the earlier
state of this problem. Later, the studies were extended for
the oxide superconductors.
As a result of experiments on mixed samples
containing La0.8Sr0.2MnO3 and La0.8Sr0.2CuO3, in the
search for a ferromagnetic-superconducting transition, the
ferromagnetic compound La0.8Sr0.2 Mn0.7Cu0.3O3+d was
prepared [2]. The superconductive composition
YBa2MnxZnxCu3-xO7-d with an onset temperature of 67.5K,
but with a wide superconducting transition, was reported
[3].
Several works have been devoted to the preparation of
three-layered YBCO-La0.7Me0.3 MnO3-YBCO materials,
to optimize the epitaxial
growth in them and the interface structure of
superlattices [4, 5].
The achievement Tc zero at 60 K for the YSr2(Cu1-
xFex)3O7-δ compound [6] and 50K in FeSr2YCu2O7.68
samples [7] were pointed out. Recently, ferromagnetic
superconductors in 1212 type layered cuprate
RuSr2GdCu2O8 were also discovered, with a bulk
superconductivity below 46K and a Curie transition at 132
K [8-13]. A comprehensive theoretical analysis of the
proximity effects in superconductor-ferromagnetic
heterostructures was made by Buzdin [14]. Practically, all
interesting effects related to the interplay between
superconductivity (S) and magnetism (F) in S/F structures
occur at the nanoscale range of the layer thicknesses.
A strong magnetic field dependence of the surface
resistance can be observed in manganite/ HTS structures at
T<Tc, due to the FMR effect [15]. Layered structures
composed of oxide HTS and FM materials have attracted
great attention for their importance in fundamental
physics, and in potential applications in spintronics [15-
19].
In our preliminary studies, superconductive behaviour
below 90K and ferromagnetic properties at room
1542 A. Staneva, A. Stoyanova-Ivanova, S. Terzieva, J. Shoumarova, K. Grigorov...
temperature were observed in sintered bulk samples
containing La(1-x)MxMnO3 (M=Pb, Sr) and YBCO [20].
The above examples demonstrated the possibility of
the coexistence of superconductivity and ferromagnetism
in polycrystalline ceramic materials or in multilayered
planar structures, but many problems arise concerning the
reproducible preparation of such materials.
The purpose in this paper is to reveal the influence of
the manganese ferromagnetic phase La0.6Pb0.4MnO3 on the
phase formation, microstructure and superconducting
properties of BSCCO based composite bulk ceramics. This
is important for the selection of an appropriate scheme for
the preparation of bulk and planar superconducting doped
materials with multifunctional properties.
2. Experimental
Powders of the Bi1.6Pb0.4Sr2Ca2Cu3Oz (2223) and
La0.6Pb0.4MnO3 phases have been obtained by the Pechini
method. The applied method was focused on the solution
preparation technique, yielding an amorphous organic
resin which can be converted to oxides by pyrolysis. It was
described for the first time in a patent published in 1967
[21] on the synthesis of titanates and niobates. The process
involved the dissolution of soluble salts in suitable
solvents that are removed by heat treatment. A weak
organic acid (citric acid) and a polyhydroxyl alcohol
(ethylene glycol), allowing esterification upon heating,
were used [22]. The obtained amorphous resin was heat
treated and transformed into fine powdered material. The
powders were mixing in the ratio 90
Bi1.6Pb0.4Sr2Ca2Cu3Oz:10 La0.6 Pb0.4 MnO3. Following this,
homogenization and pressing into pellets took place. They
were heat treated at 840oC for 60 h (30 h in air and 30 h in
O2).
The samples obtained were characterized via X-ray
diffraction using a Philips diffractometer (CuKα radiation,
quartz monochromator and pulse height analyzer). A
computer-controlled cryostat system, giving 15 K as the
lower temperature limit, was used to measure the electric
conductivity by the four-electrode method.
The microstructure of the samples was studied by
means of Zeiss EVO MA-15 Scanning Electron
Microscopy (SEM), with a LaB6 cathode. Polished
cross-sections from the samples were prepared. The
chemical composition of the samples was determined by
X-ray microanalysis, using the Energy Dispersive
Spectroscopy (EDS) method -Oxford Instruments INCA
Energy. The qualitative and quantitative analyses were
carried out at an
accelerating voltage 20 kV, which is a normal
condition for these purposes. Quantitative map (Q map)
analysis was performed on 512x400 pixels for 20 hours.
Optical images were taken with polarized light, using
Nikon Micro hot-FX optical microscopy (OM).
3. Results and discussion
X-ray phase analysis conformed the coexistence of
Bi-phases and La-manganite (Fig. 1).
Fig. 1. X-ray patterns of the composite
90 Bi1.6Pb0.4 Sr2Ca2Cu3Oz :10 La0.6 Pb0.4 MnO3.
This study shows that the applied low temperature
method is suitable for the preparation of the composites in
which are preserved the initially synthesized phases. The
method possesses some advantages, because the starting
submicron powders can be synthesized for a short time
and can be sintering at low temperature.
Fig. 2. U-T curve for the composite:
90 Bi1.6Pb0.4 Sr2Ca2Cu3Oz :10 La0.6 Pb0.4 MnO3.
The introduction of up to 10 %mass La0.6Pb0.4MnO3
phases did not influence significantly the superconducting
properties, Tc – 86.6K (Fig. 2).
BSCCO ceramics doped with ferromagnetic manganite phases 1543
Fig. 3. Optical micrograph of the composite
90 Bi1.6Pb0.4 Sr2Ca2Cu3Oz :10 La0.6 Pb0.4 MnO3.
Several bismuthate phases and a lantanium-manganite
phase have been identified by electron-probe
microanalysis (Figs. 3, 4). The crystals of the main phases
BSCCO are randomly distributed in the volume of the
sample.
Q map backscattering electron microanalysis was used
to show the distribution of different elements in a
synthesized (obtained) composite (Fig. 4). One can see
that light crystals (p. 1) are rich in Bi and contain little
quantities of Cu and Sr. Grey crystals (p. 2) are rich in Cu,
Sr and Ca. Fine crystals (p. 3) are from La0.6Pb0.4MnO3,
which is identified as an independent phase. They are
situated on the boundaries of bigger crystals. The granular
structure is due probably to a secondary re crystallization
processes, as a result of the appearance of a liquid phase. It
is evident that Cu and Pb are not uniformly distributed in
large monocrystals. They show a tendency to separate into
an independent phase. One can observe a good density and
low porosity (lack of cavities). The reason for the
superconducting transition to occur at Tc=86.6K is a result
of the presence of several Bi phases after long thermal
treatment.
4. Conclusions
A composite material was developed from submicron
powders of La-manganite and BSCCO-ceramic,
previously obtained by the Pechini method. The obtained
sample had a dense structure. The La-manganite crystals
were segregated on the boundaries with the Bi phases.
This preliminary positive result can be used for the
preparation of the many functional materials possessing
superconducting and magnetic properties in different
temperature ranges. Experiments for the quantitative
determination of magnetic and superconducting properties
are anticipated.
Fig. 4. Q map backscattering electron imag of the
composite 90 Bi1.6Pb0.4 Sr2Ca2Cu3Oz :10 La0.6 Pb0.4
MnO3. Electron probe microanalysis images showing the
composition map of different elements.
Acknowledgements
The research is financially supported by the Institute
of Solid State Physics (Grant №BK1/08), ESF grant
№7608 and Contracts with UCTM № 10 497.
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*Corresponding author: ani_sta@mail.bg, aksi_bg@abv.bg