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Superconductivity and crystal structure of Pb(Ba,Sr)2(Ln,Ca)Cu3Oy and Pb(Ba,Sr)2(Ln,Ce)2Cu3Oy(Ln: lanthanoid) with (Pb,Cu) double layers
Physica C 185-189 (1991) 619-620 North-Holland III
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SUPERCONDUCTIVITY AND CRYSTAL STRUCTUREOF Pb(Ba,Sr)~(Ln,Ca)Cu~Oyand Pb(Ba,Sr)2(Ln,Ce)2Cu3Oy(Ln:lanthanoid) WITH (Pb,Cu) DOUBLELAYER~ Ayako TOKIWA, Yasuhiko SYONO, Takeo OKU and Masayasu NAGOSHI* Institute for Materials Research, Tohoku University, Katahira, Sendai 980, Japan *Steel Research Center, NKK Corporation, Kawasaki 210, Japan Pb(Ba,Sr)p(Ln,Ca)CuaOy (Pb2212, y=7 0-8,4) and Pb(Ba,Sr) (Ln,Ce) Cu Oy (Pb2Z22,y:9 O-lO 4) were 2 3 • • The lansynthesi zed, and crystal structure, " phase transition and2superconductivity were studied. thanoid contraction was clearly observed in a relationship of 4f-electron number of Lnj+ versus cell volume of Pb2212, consistent with constant oxygen content for all of the lanthanoid substitutions. Transition temperature from oxygen rich phase to poor one was almost constant to be 580"C, in contrast to variation of the ortho-tetra transition temperature in Ba2LnCu3OY.
I,
INTRODUCTION
mined from measured d-spacings by the least
Since the discovery of superconducting
squares method. Oxygencontent was analyzed by
Pb2Sr2(Y,Ca)Cu30Y(Pb3212) by Cava et a l l . ,
the iodide titration method. Thermogravimetric
several new copper oxides with Pb containing layers were reported in these three years.
analysis (TGA) was performed in flowing I%02-N2 We
gas with a heating and cooling rate of 2°C/min.
also reported studies concerning Pb(Ba,Sr)2(Y, Ca)Cu30Y(Pb2212) with (Pb,Cu) double layer and oxygen deficient lanthanoid layer, and
3. RESULTSAND DISCUSSION Single phase of PbBaSrLnCu30y(Pb2212 ) was
Pb(Ba,Sr)2(Ln,Ce)2Cu30Y (Pb2222) with the
synthesized in I%02-N2 for all trivalent lan-
(Pb, Cu) double layer and fluorite layer 2.
thanoid ions (Ln=La-Lu). These wide range of
In this paper, crystal st-ucture, phase tran-
lanthanoid substitutions is common to the com-
sition and superconductivity ,.f lanthanoid sub-
pounds with oxygen deficient lanthanoid layer
stituted Pb2212 and Pb2222 are ~escribed, and
such as
Ba2LnCu3Oy3and Pb2Sr2LnCu30y 4.
On
these properties are discussed in comparison
the other hand, single phase of PbBao.TSrT.3Ln-
with lanthanoid substituted compounds in other
CeCu30Y (Pb2222) with fluorite layers was ob-
systems of oxide superconductors.
tained in I%02-N2 only for Ln=Sm-Tm.
2. EXPERIMENTAL
prepared for Ln=La, Pr and Nd with larger ionic
By chang-
ing sintering atmosphere from I%02 to N2, "~ w~s The specimen was prepared from a mixture of
radii.
However, in neither reducing nor oxidiz-
PbO, BaO2, Sr2Cu03, CuO and lanthanoid oxides.
ing atmosphere, substitution by Ln=Yb and Lu
The pelletized material was sintered several
with the smaller i o n i c r a d i i of Ln 3+ was
times at 830°C in I%02-N2 or in pure N2 over 24
successful, s i m i l a r to Pb32225 and Bi22226.
hours.
Both the a- and c-axes of lanthanoid s u b s t i t u t e d
The sintered pellet was subsequently
quenched into liq. N2 or slowly cooled in a fur-
Pb2212 and Pb2222 increased with increasing
nace, and a part of the specimen was annealed in
i o n i c radius, and the c - a x i s of every sp2cimen
02 at 450°C. The product was examined by X-ray
extended by about 0.16 A per a (Pb, Cu) double
powder diffraction (XPD) analysis with Cu K~
l a y e r a f t e r annealed in oxygen,
radiation.
of Pb2212 was almost constant to be 7.0 : o r t~e
The unit cell dimensions were deter-
0921-4534/91/$03.50 © 1991 -Elsevier Scicnce Publishers B.V. All righL~ rcser~cd.
Oxyget~ co~te~t
A. Tokiwa et at / Superconductivityand c~stalstructureof Pb(Ba,$r)2(Ln,Ca )Cu aOy
620
L.z pt Co Nd Pm~ml~ GdTb DyHo Er Tmy.oLu
,
4
"
•
:
,
20O
•
•
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i
,|
,
i
.
.
.
.
.
.
.
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,
:
,
,.
•
60O TEMPERATURE( ° C )
"d FIROM1%O2 ~) i ~ 3 ~ 5 (~ ; 8. . 9. .I0i! . . 121314'
:
400
I"
,.
8O0
Thermogravimetry o f PbBaSrLnCu~Oy(Ln=La, Gd and Lu) started from the quencBed specimen
NUMBEROF 4f-ELECTRON lated to the ionic size of lanthanoid ions, in FIGURE I, Relationship between number of 4f-electron and cell volume of PbBaSrLnCu30Y
contrast to variation of ortho-tetra transition temperature with the size of lanthanoid ions substituted in
quenched specimen, and to be 8,4 for oxygen an-
Ba2LnCu3Oy7.
Pb(Ba,Sr)2(Y,Ca)Cu30Y showed superconduc-
nealed ones with all the lanthanoid elements,
t i v i t y with maximum Tc of 65 K, as reported in
and that of Pb2222 was also constant to be 8.0
our previous papers2,
and 9.4 for quenched and oxygen annealed
tion by Ca for lanthanoid will also leads to su-
specimens, respectively.
perconductivity, and now being studied. In
Relationship between
Similar partial substitu-
number of 4f-electron of Ln3+ versus cell volume
Pb2222, superconductivity has not been observed,
of PbBaSrLnCu30y is shown in Fig. I.
similar to Pb32225, although temperature depen-
The lan-
thanoid contraction is clearly observed in both
dence of electric r e s i s t i v i t y changed from semi-
quenched and oxygen annealed specimens, consis-
conducting to metallic by partial substitution
tent with constant oxygen content,
of Ln3+ on Ce4+ site and by high oxygen-pressure
In Pb2222,
similar correlation was not observed, probably due to slight oxygen deficiency from stoichio-
treatment. In summary, lanthanoid substitutions of
merry for La, Pr and Nd substitutions syn-
Pb2212 and Pb2222 showed common fashion to the
thesized in N2,
other cooper oxide superconductors, except that
Some examples of weight change in heating and
phase transition temperature of Pb2212 and
cooling process accompanied with oxygen absorp-
Pb2222 was l i t t l e influenced by ionic size of
tion and desorption of PbBaSrLnCu30Y are shown
lanthanoid elements.
in Fig. 2,
The rate of oxygen absorption in
Pb2212 seemed to be less with decreasing ionic radius of Ln3+,
The transition temperature from
oxygen rich phase to poor one, which was determined by TGA, was almost constant to be 580°C in Pb2212 and Pb2222 for al] lanthanoid elements. I t is indicated that the temperature is mainly controlled by reactivity of (Pb, Cu) double ]ayer with oxygen, and not directly r e -
REFERENCES I. R.J, Cava et al., Nature 336 (1988) 211, 2. A. Tokiwa et al., Physica C 161 (1989) 459, 16~8 (1990) 285, __170 (1990) 437, 17_.22(1990) 155.
3, 5. Ohshima and T. Wakiyama., Jpn. J. Appl. Phys. 266 (1987) L512. 4. L,F, Schneemeyer et al,, Chem. Mater. 1 (1989) 548. 5, A.L. Kharlanov et al., Physica C 169 (1990)469, 6. T. Arima et al., Physica C 168 ( I ~ ) 79. 7, Y. Nakabayashi et al., Jpn.T. Appl. Phys. 27 (I988) L64.
IIII
I
I
II]I
I
I
SUPERCONDUCTIVITY AND CRYSTAL STRUCTUREOF Pb(Ba,Sr)~(Ln,Ca)Cu~Oyand Pb(Ba,Sr)2(Ln,Ce)2Cu3Oy(Ln:lanthanoid) WITH (Pb,Cu) DOUBLELAYER~ Ayako TOKIWA, Yasuhiko SYONO, Takeo OKU and Masayasu NAGOSHI* Institute for Materials Research, Tohoku University, Katahira, Sendai 980, Japan *Steel Research Center, NKK Corporation, Kawasaki 210, Japan Pb(Ba,Sr)p(Ln,Ca)CuaOy (Pb2212, y=7 0-8,4) and Pb(Ba,Sr) (Ln,Ce) Cu Oy (Pb2Z22,y:9 O-lO 4) were 2 3 • • The lansynthesi zed, and crystal structure, " phase transition and2superconductivity were studied. thanoid contraction was clearly observed in a relationship of 4f-electron number of Lnj+ versus cell volume of Pb2212, consistent with constant oxygen content for all of the lanthanoid substitutions. Transition temperature from oxygen rich phase to poor one was almost constant to be 580"C, in contrast to variation of the ortho-tetra transition temperature in Ba2LnCu3OY.
I,
INTRODUCTION
mined from measured d-spacings by the least
Since the discovery of superconducting
squares method. Oxygencontent was analyzed by
Pb2Sr2(Y,Ca)Cu30Y(Pb3212) by Cava et a l l . ,
the iodide titration method. Thermogravimetric
several new copper oxides with Pb containing layers were reported in these three years.
analysis (TGA) was performed in flowing I%02-N2 We
gas with a heating and cooling rate of 2°C/min.
also reported studies concerning Pb(Ba,Sr)2(Y, Ca)Cu30Y(Pb2212) with (Pb,Cu) double layer and oxygen deficient lanthanoid layer, and
3. RESULTSAND DISCUSSION Single phase of PbBaSrLnCu30y(Pb2212 ) was
Pb(Ba,Sr)2(Ln,Ce)2Cu30Y (Pb2222) with the
synthesized in I%02-N2 for all trivalent lan-
(Pb, Cu) double layer and fluorite layer 2.
thanoid ions (Ln=La-Lu). These wide range of
In this paper, crystal st-ucture, phase tran-
lanthanoid substitutions is common to the com-
sition and superconductivity ,.f lanthanoid sub-
pounds with oxygen deficient lanthanoid layer
stituted Pb2212 and Pb2222 are ~escribed, and
such as
Ba2LnCu3Oy3and Pb2Sr2LnCu30y 4.
On
these properties are discussed in comparison
the other hand, single phase of PbBao.TSrT.3Ln-
with lanthanoid substituted compounds in other
CeCu30Y (Pb2222) with fluorite layers was ob-
systems of oxide superconductors.
tained in I%02-N2 only for Ln=Sm-Tm.
2. EXPERIMENTAL
prepared for Ln=La, Pr and Nd with larger ionic
By chang-
ing sintering atmosphere from I%02 to N2, "~ w~s The specimen was prepared from a mixture of
radii.
However, in neither reducing nor oxidiz-
PbO, BaO2, Sr2Cu03, CuO and lanthanoid oxides.
ing atmosphere, substitution by Ln=Yb and Lu
The pelletized material was sintered several
with the smaller i o n i c r a d i i of Ln 3+ was
times at 830°C in I%02-N2 or in pure N2 over 24
successful, s i m i l a r to Pb32225 and Bi22226.
hours.
Both the a- and c-axes of lanthanoid s u b s t i t u t e d
The sintered pellet was subsequently
quenched into liq. N2 or slowly cooled in a fur-
Pb2212 and Pb2222 increased with increasing
nace, and a part of the specimen was annealed in
i o n i c radius, and the c - a x i s of every sp2cimen
02 at 450°C. The product was examined by X-ray
extended by about 0.16 A per a (Pb, Cu) double
powder diffraction (XPD) analysis with Cu K~
l a y e r a f t e r annealed in oxygen,
radiation.
of Pb2212 was almost constant to be 7.0 : o r t~e
The unit cell dimensions were deter-
0921-4534/91/$03.50 © 1991 -Elsevier Scicnce Publishers B.V. All righL~ rcser~cd.
Oxyget~ co~te~t
A. Tokiwa et at / Superconductivityand c~stalstructureof Pb(Ba,$r)2(Ln,Ca )Cu aOy
620
L.z pt Co Nd Pm~ml~ GdTb DyHo Er Tmy.oLu
,
4
"
•
:
,
20O
•
•
i
i
,|
,
i
.
.
.
.
.
.
.
l
i
:
,
:
,
,.
•
60O TEMPERATURE( ° C )
"d FIROM1%O2 ~) i ~ 3 ~ 5 (~ ; 8. . 9. .I0i! . . 121314'
:
400
I"
,.
8O0
Thermogravimetry o f PbBaSrLnCu~Oy(Ln=La, Gd and Lu) started from the quencBed specimen
NUMBEROF 4f-ELECTRON lated to the ionic size of lanthanoid ions, in FIGURE I, Relationship between number of 4f-electron and cell volume of PbBaSrLnCu30Y
contrast to variation of ortho-tetra transition temperature with the size of lanthanoid ions substituted in
quenched specimen, and to be 8,4 for oxygen an-
Ba2LnCu3Oy7.
Pb(Ba,Sr)2(Y,Ca)Cu30Y showed superconduc-
nealed ones with all the lanthanoid elements,
t i v i t y with maximum Tc of 65 K, as reported in
and that of Pb2222 was also constant to be 8.0
our previous papers2,
and 9.4 for quenched and oxygen annealed
tion by Ca for lanthanoid will also leads to su-
specimens, respectively.
perconductivity, and now being studied. In
Relationship between
Similar partial substitu-
number of 4f-electron of Ln3+ versus cell volume
Pb2222, superconductivity has not been observed,
of PbBaSrLnCu30y is shown in Fig. I.
similar to Pb32225, although temperature depen-
The lan-
thanoid contraction is clearly observed in both
dence of electric r e s i s t i v i t y changed from semi-
quenched and oxygen annealed specimens, consis-
conducting to metallic by partial substitution
tent with constant oxygen content,
of Ln3+ on Ce4+ site and by high oxygen-pressure
In Pb2222,
similar correlation was not observed, probably due to slight oxygen deficiency from stoichio-
treatment. In summary, lanthanoid substitutions of
merry for La, Pr and Nd substitutions syn-
Pb2212 and Pb2222 showed common fashion to the
thesized in N2,
other cooper oxide superconductors, except that
Some examples of weight change in heating and
phase transition temperature of Pb2212 and
cooling process accompanied with oxygen absorp-
Pb2222 was l i t t l e influenced by ionic size of
tion and desorption of PbBaSrLnCu30Y are shown
lanthanoid elements.
in Fig. 2,
The rate of oxygen absorption in
Pb2212 seemed to be less with decreasing ionic radius of Ln3+,
The transition temperature from
oxygen rich phase to poor one, which was determined by TGA, was almost constant to be 580°C in Pb2212 and Pb2222 for al] lanthanoid elements. I t is indicated that the temperature is mainly controlled by reactivity of (Pb, Cu) double ]ayer with oxygen, and not directly r e -
REFERENCES I. R.J, Cava et al., Nature 336 (1988) 211, 2. A. Tokiwa et al., Physica C 161 (1989) 459, 16~8 (1990) 285, __170 (1990) 437, 17_.22(1990) 155.
3, 5. Ohshima and T. Wakiyama., Jpn. J. Appl. Phys. 266 (1987) L512. 4. L,F, Schneemeyer et al,, Chem. Mater. 1 (1989) 548. 5, A.L. Kharlanov et al., Physica C 169 (1990)469, 6. T. Arima et al., Physica C 168 ( I ~ ) 79. 7, Y. Nakabayashi et al., Jpn.T. Appl. Phys. 27 (I988) L64.