J Low Temp Phys (2008) 153: 26–34
DOI 10.1007/s10909-008-9820-8
Enhanced Superconductivity
in (Cu
0.5
Tl
0.25
Cs
0.25
)Ba
2
Ca
2
Cu
3
O
10−δ
by Cs Doping
Nawazish A. Khan · Safeer Hussain
Received: 12 January 2008 / Accepted: 28 July 2008 / Published online: 20 August 2008
© Springer Science+Business Media, LLC 2008
Abstract The self doping of carriers in CuO
2
planes (accomplished through post
annealing in air, N
2
and O
2
atmospheres in previous studies) is replaced by a more
efficient alkali metal dopant such as Cs. The doping of Cs in the Cu
0.5
Tl
0.5
Ba
2
O
4−δ
charge reservoir of Cu
0.5
Tl
0.5
Ba
2
Ca
2
Cu
3
O
10−δ
superconductors has been found
to enhance its superconducting properties. Enhanced superconductivity parameters,
such as T
c
, H
c
and J
c
, most likely arise from the enhanced doping efficiency of
Cu
0.5
Tl
0.25
Cs
0.25
Ba
2
O
4−δ
charge reservoir layer; since the alkali metals are known
to lose their outermost “s-orbital” electron, which could be supplied to conducting
CuO
2
planes. The distance between efficiently doped CuO
2
planes is reduced by Be
and Mg doping at the Ca Sites. The quantity of diamagnetism and zero resistivity
critical temperature [T
c
(R = 0)] are suppressed by these substitutions. The post-
annealing of the Cs doped samples further enhances their superconducting proper-
ties; oxygen doping most likely promotes the optimum holes concentration in the
superconducting state in the Cs doped samples. These observations have also shown
that the free carrier density plays a significant role in the mechanism of superconduc-
tivity which was accomplished by synthesizing (Cu
0.5
Tl
0.25
Cs
0.25
)Ba
2
Ca
2
Cu
3
O
10−δ
superconductors.
Keywords (Cu
0.5
Tl
0.25
Cs
0.25
)Ba
2
Ca
2
Cu
3
O
10−δ
superconductors · Higher
T
c
(R = 0) with Cs doping · Enhanced diamagnetism · Post-annealing
PACS 74.76.-w · 74.76.Bz · 74.72.-h · 74.72.Jt
N.A. Khan ( ) · S. Hussain
Materials Science Laboratory, Department of Physics, Quaid-i-Azam University, Islamabad, Pakistan
e-mail: nawazishalik@yahoo.com