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Preparation of YBa2Cu4O8 under an atmosphere of oxygen gas
Physica C 185-189 (1991) 491-492 North-Holland
IHt.I';I'ARA'I'ION OF YBa2('ua()s UNI)ER AN :Vi'M()SI'IIIHH': ()F OXY(;I':N (;AS
Lu qing feng, Katsunori MORI, Yosikazu ISIKAWA, Kazuo KAMIGAKI, and Kazuo ROKUDO a College of Liberal Arts, Toyama University, 3190 Gofuku, Toyama 930, Japan a T h e Hokuriku Electric Power Co., Inc., 2-5--'1 Hisakata-machi, Toyama 930, Japan
YBa2CuaOs (1-2-4 phase) superconductor with transition temperature at Tc.o,tI =82K is synthesized via a solidstate reaction from a mixture of Y2Oa, BaCOa and CuO and a mixture of YBa2CuaOr and CuO in flowing oxygen gas. Nearly phase-pure 1-2-4 compound, determined by X-ray powder diffraction, electron probe X-ray microanalyzer and electrical resistivity, has been obtained.
1. INTRODUCTION lligh oxygen pressure was considered necessary to synthesize bulk YBa2Cu4Os (1-2-4 phase) 1-4, and because of a specialized equipment needed, this compound has not been investigated extensively. We report here a preparation o1" YBa,~Cu4Os under an atmosphere of oxygen gas. 2. MATERIAl, SYNTI1ESIS AND SPECIMEN PREPARATION The 1-2-,I compound, YBa~Cu4Os, was prepared via a solid-state reaction from a mixture of Y2()3, BaCOa and CuO (99.99% for each). Two series were carried out. In the first series, the starting stoichiometry was of Y:Ba:Cu = h2:.t in nominal composition (sample #1 and #2) and in the second series, the starting was from the mixture of YBa2Cu3Or and CuO TABLE I. Details of heating conditions. Sample
#I
#2
#3
Heating condition 1.900°C,12h 2.8000C,i0h 3.850*C,72h (3.twice)
Cooling rate 200*C/h ~O0°C/h 20°C/h
Atmosphere
1.750°C,24h 2.830"C,72h 3.850°C,72h (3.twice)
400°C/h
Ar,O 2 gas air 02 gas
1.850°C,72h (3 times)
20°C/h
20°C/h
02 gas
(sample #3). Table I.
3. RESULTS AND DISCUSSION The observed X-ray diffraction patterns for the samples of #1, #2, and #3 are shown in Fig.l. Each pattern in Fig.l indicales that the materials consist mostly of the 1-2-.t phase. To investigate the composition of Y, Ba and Cu, the electron probe X-ray microanalyzer(El'MA) was used in about 13 parts of each s~mple. The average compt,sitions(atomic %) of elements are shown in "Fable !1. The rate of stoichio-
L_A #2
t
z/oO--, .ib o i
20
02 gas
The details of heat treatments are in
;
40 50 60 70 20 ( d e g r e e ) FIGURE 1. X-raydiffractiunpatterns.
0921-4534191/$03.50 © 1991 - Elsevier Science Publishers B.V. All rights reserved.
30
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Lu qing feng et at / Preparation of YBa2Cu40 s under an atmosphere of o:cygen gas
492
TABLE II, Values of composition analyzed by EPMA (atomic %). Sample #1 #2 #3
'~(z)
Ba(Z)
Cu(%)
14,2±1,2 1.3,8¢1,2 14,6,±1.7
25.3±1.5 24,5~2.0 25.7~2o6
60.5~1,7 61.6±2.5 60.0~2.5
metric composition o1"YBaaCu.lOs is Y--14.3 atomic%, Ba=28.6 atomic% and Cu=57.1 atomic%, and that ,'~f YBa~CuaO¢ is Y=16.7 atomic%, Ba--33.3 atomic% and Cu=50.0 atomic%. As can be seen in Table II, the rate of the analyzed composition,,: of the elements is close to that o1"YBa2Cu4()s, The electrical resistivity was measured by a standard DC method with four-probe terminals. The tern-
"-- .G
TABLE II!. Superconducting transition temperature. #
1
#
2
#
3
To.o,, (K)
94.0
94.0
95.0
T~,o. (K)
81.0
83.0
86.0
perature dependence of the electrical resistivity for each sample is shown in Fig.2. The behaviour is clearly metallic with a resistivity ratio, p(3OOK)/p(lOOK), of about 3. The resistivity curve extrapolated linearly below T± leads to negative resistivity values. Therefore the resistivity for YBa2Cu4Os(I-2-4) is considered to behave like as the Bloch-Gr{ineisen type. A superconducting transition temperature is observed with T¢,o,,(resistance begins to drop.) and Tc,o.t! (resistance becomes zero.), which are shown in Table III. Since the values of T~,o, seem to be high, the 1-2-3 phase, YBa2CuaOr, might be contained a little in the 1-2-4 phase.
~. .d. "'4 .2 b...
"-'0 O3 0
50 100 1 5 0 2 0 0 2 5 0 3 0 0 TEMPERA TURE (K) I
~1.2
_#2
~.8 "h.-
?
Ctj C~
E
"
I I [ I I 50 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 TEMPERA TURE (If)
0
I.2
i¢y
¢
4.
°
L
I
I
1
I
#3
°
¢.o
I I I [ [ 50 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 TEMPERA TURE (K) FIGURE 2. Temperature dependence of electrical resistivity. cc.
0
4. SUMMARY In conclusion, we have synthesized YBa2Cu4Os(l2-4) compound in an atmosphere of oxygen for two series. We believe that YBa2CuaOs compound would be synthesized by taking enough time for sintering around 750-,.850° C.
ACKNOWLEDGEMENTS We thank Mr.E. Segawa, the Hokuriku Power Co., Inc., for supporting this work. This work was supported by Research and Development Center at Toyama University and the ttokuriku Power Co., Inc.. REFERENCES 1. T.Miyatake, S.Gotoh, N.Koshizuka, and S.Tanaka, Nature 341 (1989) 41. 2. T.Miyatake, K.Yamaguchi, T.Tanaka, S.Gotoh, N.Koshizuka and S.Tanaka, Physica C 160 (1989) .511. 3. D.E.Morris, J.H.Nickel, J.Y.Wei, Y.G.Asmar, J.S.Scott, U..M.Scheven, C.T.ltultgren, and A.G. Markeh, Phys. Rev. B 39 (1989) 7347. 4. J.Karpinski, S.Rusiecki, E.Kaldis, B.Bucher and E.Jiek, Physica C 160 (1989) 449.
IHt.I';I'ARA'I'ION OF YBa2('ua()s UNI)ER AN :Vi'M()SI'IIIHH': ()F OXY(;I':N (;AS
Lu qing feng, Katsunori MORI, Yosikazu ISIKAWA, Kazuo KAMIGAKI, and Kazuo ROKUDO a College of Liberal Arts, Toyama University, 3190 Gofuku, Toyama 930, Japan a T h e Hokuriku Electric Power Co., Inc., 2-5--'1 Hisakata-machi, Toyama 930, Japan
YBa2CuaOs (1-2-4 phase) superconductor with transition temperature at Tc.o,tI =82K is synthesized via a solidstate reaction from a mixture of Y2Oa, BaCOa and CuO and a mixture of YBa2CuaOr and CuO in flowing oxygen gas. Nearly phase-pure 1-2-4 compound, determined by X-ray powder diffraction, electron probe X-ray microanalyzer and electrical resistivity, has been obtained.
1. INTRODUCTION lligh oxygen pressure was considered necessary to synthesize bulk YBa2Cu4Os (1-2-4 phase) 1-4, and because of a specialized equipment needed, this compound has not been investigated extensively. We report here a preparation o1" YBa,~Cu4Os under an atmosphere of oxygen gas. 2. MATERIAl, SYNTI1ESIS AND SPECIMEN PREPARATION The 1-2-,I compound, YBa~Cu4Os, was prepared via a solid-state reaction from a mixture of Y2()3, BaCOa and CuO (99.99% for each). Two series were carried out. In the first series, the starting stoichiometry was of Y:Ba:Cu = h2:.t in nominal composition (sample #1 and #2) and in the second series, the starting was from the mixture of YBa2Cu3Or and CuO TABLE I. Details of heating conditions. Sample
#I
#2
#3
Heating condition 1.900°C,12h 2.8000C,i0h 3.850*C,72h (3.twice)
Cooling rate 200*C/h ~O0°C/h 20°C/h
Atmosphere
1.750°C,24h 2.830"C,72h 3.850°C,72h (3.twice)
400°C/h
Ar,O 2 gas air 02 gas
1.850°C,72h (3 times)
20°C/h
20°C/h
02 gas
(sample #3). Table I.
3. RESULTS AND DISCUSSION The observed X-ray diffraction patterns for the samples of #1, #2, and #3 are shown in Fig.l. Each pattern in Fig.l indicales that the materials consist mostly of the 1-2-.t phase. To investigate the composition of Y, Ba and Cu, the electron probe X-ray microanalyzer(El'MA) was used in about 13 parts of each s~mple. The average compt,sitions(atomic %) of elements are shown in "Fable !1. The rate of stoichio-
L_A #2
t
z/oO--, .ib o i
20
02 gas
The details of heat treatments are in
;
40 50 60 70 20 ( d e g r e e ) FIGURE 1. X-raydiffractiunpatterns.
0921-4534191/$03.50 © 1991 - Elsevier Science Publishers B.V. All rights reserved.
30
-kr
Lu qing feng et at / Preparation of YBa2Cu40 s under an atmosphere of o:cygen gas
492
TABLE II, Values of composition analyzed by EPMA (atomic %). Sample #1 #2 #3
'~(z)
Ba(Z)
Cu(%)
14,2±1,2 1.3,8¢1,2 14,6,±1.7
25.3±1.5 24,5~2.0 25.7~2o6
60.5~1,7 61.6±2.5 60.0~2.5
metric composition o1"YBaaCu.lOs is Y--14.3 atomic%, Ba=28.6 atomic% and Cu=57.1 atomic%, and that ,'~f YBa~CuaO¢ is Y=16.7 atomic%, Ba--33.3 atomic% and Cu=50.0 atomic%. As can be seen in Table II, the rate of the analyzed composition,,: of the elements is close to that o1"YBa2Cu4()s, The electrical resistivity was measured by a standard DC method with four-probe terminals. The tern-
"-- .G
TABLE II!. Superconducting transition temperature. #
1
#
2
#
3
To.o,, (K)
94.0
94.0
95.0
T~,o. (K)
81.0
83.0
86.0
perature dependence of the electrical resistivity for each sample is shown in Fig.2. The behaviour is clearly metallic with a resistivity ratio, p(3OOK)/p(lOOK), of about 3. The resistivity curve extrapolated linearly below T± leads to negative resistivity values. Therefore the resistivity for YBa2Cu4Os(I-2-4) is considered to behave like as the Bloch-Gr{ineisen type. A superconducting transition temperature is observed with T¢,o,,(resistance begins to drop.) and Tc,o.t! (resistance becomes zero.), which are shown in Table III. Since the values of T~,o, seem to be high, the 1-2-3 phase, YBa2CuaOr, might be contained a little in the 1-2-4 phase.
~. .d. "'4 .2 b...
"-'0 O3 0
50 100 1 5 0 2 0 0 2 5 0 3 0 0 TEMPERA TURE (K) I
~1.2
_#2
~.8 "h.-
?
Ctj C~
E
"
I I [ I I 50 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 TEMPERA TURE (If)
0
I.2
i¢y
¢
4.
°
L
I
I
1
I
#3
°
¢.o
I I I [ [ 50 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 TEMPERA TURE (K) FIGURE 2. Temperature dependence of electrical resistivity. cc.
0
4. SUMMARY In conclusion, we have synthesized YBa2Cu4Os(l2-4) compound in an atmosphere of oxygen for two series. We believe that YBa2CuaOs compound would be synthesized by taking enough time for sintering around 750-,.850° C.
ACKNOWLEDGEMENTS We thank Mr.E. Segawa, the Hokuriku Power Co., Inc., for supporting this work. This work was supported by Research and Development Center at Toyama University and the ttokuriku Power Co., Inc.. REFERENCES 1. T.Miyatake, S.Gotoh, N.Koshizuka, and S.Tanaka, Nature 341 (1989) 41. 2. T.Miyatake, K.Yamaguchi, T.Tanaka, S.Gotoh, N.Koshizuka and S.Tanaka, Physica C 160 (1989) .511. 3. D.E.Morris, J.H.Nickel, J.Y.Wei, Y.G.Asmar, J.S.Scott, U..M.Scheven, C.T.ltultgren, and A.G. Markeh, Phys. Rev. B 39 (1989) 7347. 4. J.Karpinski, S.Rusiecki, E.Kaldis, B.Bucher and E.Jiek, Physica C 160 (1989) 449.