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Tl0.75Pb0.20Sb0.05Ca2Ba3Cu4Oy high Tc superconductor
PhysicaC 162-164 (1989) 995-996 North-Holland
T10.75Pb0.20Sb0.05Ca2Ba3CU4Oy
HIGH Tc SUPERCONDUCTOR
I.Z. Kostadinov, M.D. Mateev, J. Tihov, V. Skumriev, E. Tsakin, O. Petrov~ E. Dinolova~ V. Kovachev ++ Faculty of Physics, Sofia University, 1126 Sofia, BULGARIA, +Institute of Applied Mineralogy, Bulg. Acad. Sci., Sofia, BULGARIA, ++Institute of Solid State Physics, Bulg. Acad. Sci., Sofia, BULGARIA
A new T1 based high T c superconducting phase was studied. The pellets were prepared from nitrates and were found to be single phased. The critical temperature was determined to be 121K. The X-ray powder diffraction demonstrated tetragonal structure with c = 31.9A. The S~M analysis also indicates monophase composition.
i. INTRODUCTION
2. EXPERIMENTAL
The T1 based high temperature superconductors
The solution of high purity nitrates of
(HTS) are of considerable interest I-3. The high-
the constituent metals
est stable zero resistance state temperature of
Cu) was dried and dicomposed a£ 780°C. Pel-
125K was found in Tl2Ba2Ca2CUsOx 2. It appeared,
lets were prepared by annealing in oxygen at-
however,
mosphere at different temperatures varying
that the T1 based pellets are often
(TI, Pb, Sb, Ba, Ca,
multiphased and there are many stable phases of
from 820°C to 915°C resulting in different
the compound TI-Ba-Ca-Cu-O.
critical temperatures.
It seems that grow-
The phase with 121K
ing of single phase crystals and thin films
was annealed in oxygen atmosphere at 891°C
faces some difficulties.
for 3 min. The SEM analysis with standards
The complete des-
cription of the properties of the different
established an average composition close to
phases of T1 based HTS is therefore much more
the starting one T10.75Pb0.20Sb0.05Ca2BasCuaO v
complicated.
n~mely
The substitution of T1 with Pb can stabilize some phases and that is why a study of (TIPbSb) lCa2-Ba2-Cu4-Oy compound TIPb-c)
(hereafter refered as
was carried out. We observed several
superconducting phases in this system marked by the corresponding highest zero resistance state temperatures T c - 90, 102, 121K. More frequently we met the phases with 102K and 90K, but varying the technological conditions we succeeded in selecting the 121K phase. Here we report some of the results we obtained for both 102K and 121K samples.
0921-4534/89/$03.50 © Elsevier Science Publishers B.V. (North-Holland)
(Tl+Pb) iCa2Ba4.1Cus.6Oy.
The X-ray
powder diffraction spectrum of this sample is shown in Fig.1. A very small amount of CuO (less than 5%) was detected in the sample. A well pronounced peak at low angles is present also. It correponds to the value of the o c parameter of the tetragonal cell c - 31.9A. o The value of a = b is estimated of 3.84A. The observed difference between the c parameo ters of 2223 phase (35~6A) and o u r result 31.9~
can be related to a removement of a
Ca-O containing layer.
I.Z. Kostadinov et al. / Tlo. zsPbo.eoSbo.osCa zBa 3Cu~Or high 7"
996
0.4
0.2
0.0
~o
-0.2
7
.o
-0.4
"x -o.e -0.8 -t.O
-1.2 0
T.K
FIGURE 1
FIGURE 3
X-ray powder diffraction spectrum of the 121K phase of TiPb-c.
The resistivity temperature dependence of this sample is shown in Fig.2.
Temperature dependence of the Re(X') and Im (X") parts of the AC susceptibility in field 24 A/m. (between 14K and 120K) u[~on worming
(Fig.3).
The data obtained were corrected for diamagnetiz±ng effect 4. The real glnary
(X') and the ima-
(X") components are -I and 0 respecti-
R.,~¢m
vely in large temperature range, suggesting for complete diamagnetic shielding° The onset .j. of the diamagnetic signal was observed at T
/ /
;,5
/
= IO4K.
3. CONCLUSIONS
/ ~,oo
c
We have succeeded in separating two phases T.K 60
~'oo
of the TiPb-c compound with zero resistance state at 102 and 121K, respectively.
FIGURE 2 Resistivity vs. temperature of the 121K phase.
The phase
with T
= 121K was found to be tetragonal with c o o c = 31.9A and a = 3.84A.
REFERENCES
The phase with zero resistance state up to 102K
prepared by annealing in oxygen atmos-
was
phere for 3min at 820K followed by quenching, grinding, 915K.
I. ZoZ. Sheng and A.M. Hermann, Nature, (1988) 55, 138. 2. S.S. Parkin et al., Phys.Rev.Lett, (1988) 2539.
60
and secondary annealing for 6min at
The product was remarkably homogeneous
3. I.Z. Kostadinov et al., Physica C 156 (1988) 427.
and its resistance abruptly turned to zero at 4. D.-X. Chen, unpublished result. Tc • The complex AC susceptibility was measured in AC field 24 A/m as a function of temperature
332
T10.75Pb0.20Sb0.05Ca2Ba3CU4Oy
HIGH Tc SUPERCONDUCTOR
I.Z. Kostadinov, M.D. Mateev, J. Tihov, V. Skumriev, E. Tsakin, O. Petrov~ E. Dinolova~ V. Kovachev ++ Faculty of Physics, Sofia University, 1126 Sofia, BULGARIA, +Institute of Applied Mineralogy, Bulg. Acad. Sci., Sofia, BULGARIA, ++Institute of Solid State Physics, Bulg. Acad. Sci., Sofia, BULGARIA
A new T1 based high T c superconducting phase was studied. The pellets were prepared from nitrates and were found to be single phased. The critical temperature was determined to be 121K. The X-ray powder diffraction demonstrated tetragonal structure with c = 31.9A. The S~M analysis also indicates monophase composition.
i. INTRODUCTION
2. EXPERIMENTAL
The T1 based high temperature superconductors
The solution of high purity nitrates of
(HTS) are of considerable interest I-3. The high-
the constituent metals
est stable zero resistance state temperature of
Cu) was dried and dicomposed a£ 780°C. Pel-
125K was found in Tl2Ba2Ca2CUsOx 2. It appeared,
lets were prepared by annealing in oxygen at-
however,
mosphere at different temperatures varying
that the T1 based pellets are often
(TI, Pb, Sb, Ba, Ca,
multiphased and there are many stable phases of
from 820°C to 915°C resulting in different
the compound TI-Ba-Ca-Cu-O.
critical temperatures.
It seems that grow-
The phase with 121K
ing of single phase crystals and thin films
was annealed in oxygen atmosphere at 891°C
faces some difficulties.
for 3 min. The SEM analysis with standards
The complete des-
cription of the properties of the different
established an average composition close to
phases of T1 based HTS is therefore much more
the starting one T10.75Pb0.20Sb0.05Ca2BasCuaO v
complicated.
n~mely
The substitution of T1 with Pb can stabilize some phases and that is why a study of (TIPbSb) lCa2-Ba2-Cu4-Oy compound TIPb-c)
(hereafter refered as
was carried out. We observed several
superconducting phases in this system marked by the corresponding highest zero resistance state temperatures T c - 90, 102, 121K. More frequently we met the phases with 102K and 90K, but varying the technological conditions we succeeded in selecting the 121K phase. Here we report some of the results we obtained for both 102K and 121K samples.
0921-4534/89/$03.50 © Elsevier Science Publishers B.V. (North-Holland)
(Tl+Pb) iCa2Ba4.1Cus.6Oy.
The X-ray
powder diffraction spectrum of this sample is shown in Fig.1. A very small amount of CuO (less than 5%) was detected in the sample. A well pronounced peak at low angles is present also. It correponds to the value of the o c parameter of the tetragonal cell c - 31.9A. o The value of a = b is estimated of 3.84A. The observed difference between the c parameo ters of 2223 phase (35~6A) and o u r result 31.9~
can be related to a removement of a
Ca-O containing layer.
I.Z. Kostadinov et al. / Tlo. zsPbo.eoSbo.osCa zBa 3Cu~Or high 7"
996
0.4
0.2
0.0
~o
-0.2
7
.o
-0.4
"x -o.e -0.8 -t.O
-1.2 0
T.K
FIGURE 1
FIGURE 3
X-ray powder diffraction spectrum of the 121K phase of TiPb-c.
The resistivity temperature dependence of this sample is shown in Fig.2.
Temperature dependence of the Re(X') and Im (X") parts of the AC susceptibility in field 24 A/m. (between 14K and 120K) u[~on worming
(Fig.3).
The data obtained were corrected for diamagnetiz±ng effect 4. The real glnary
(X') and the ima-
(X") components are -I and 0 respecti-
R.,~¢m
vely in large temperature range, suggesting for complete diamagnetic shielding° The onset .j. of the diamagnetic signal was observed at T
/ /
;,5
/
= IO4K.
3. CONCLUSIONS
/ ~,oo
c
We have succeeded in separating two phases T.K 60
~'oo
of the TiPb-c compound with zero resistance state at 102 and 121K, respectively.
FIGURE 2 Resistivity vs. temperature of the 121K phase.
The phase
with T
= 121K was found to be tetragonal with c o o c = 31.9A and a = 3.84A.
REFERENCES
The phase with zero resistance state up to 102K
prepared by annealing in oxygen atmos-
was
phere for 3min at 820K followed by quenching, grinding, 915K.
I. ZoZ. Sheng and A.M. Hermann, Nature, (1988) 55, 138. 2. S.S. Parkin et al., Phys.Rev.Lett, (1988) 2539.
60
and secondary annealing for 6min at
The product was remarkably homogeneous
3. I.Z. Kostadinov et al., Physica C 156 (1988) 427.
and its resistance abruptly turned to zero at 4. D.-X. Chen, unpublished result. Tc • The complex AC susceptibility was measured in AC field 24 A/m as a function of temperature
332