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Application of oxygen controlled melt growth (OCMG) in ternary RE123 systems
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PHYSICA ®
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ELSEVIER
Physica C 282-287 (1997) 503-504
APPLICATION OF OXYGEN CONTROLLED MELT GROWTH (OCMG) IN TERNARY RE123 SYSTEMS M. Muralidhar", H.S. Chauhan", T. Saitohb, K. Segawab, K. Kamadab and M. Murakami" ·SRL-ISTEC, 1-16-25 Shibaura, Minato-Ku, Tokyo-l05, Japan bIwate Industrial Research Institute, 3-35-2, Iioka-Shinden, Morioka, Iwate-020, Japan The detail investigations on growth and superconducting properties of ternary RE 123 systems have been done employing XRD, TEM, SEM, optical microscopy and DC magnetization techniques. XRD results confirmed that in all these systems the main phase was 123 with inclusions of small amount of second phase. The DTA, TEM, SEM and optical microscopy investigations revealed that even in the presence of three rare-earths the matrix RE123 was very uniform. The SQUID measurements on the post annealed samples showed that superconducting transitions Tc (onset) are in the range of 93-95.3K. The highest Jc value obtained in this series of systems was about
50000 Ncm 2 at 2T.
l.INTRODUCTION The critical current density (J c), in high temperature superconductors, is one of the most important parameter for their practical applications. However, the critical current density of high temperature superconductor suddenly decreases with increasing temperature and magnetic field. The recent developments in oxygen controlled melt growth (OCMG) has overcome this problem and made it possible to fabricate the superconductors with higher and sharp superconducting transitions (Tc) and larger critical current density (JJ in the RE123 (RE: Nd, Sm and Eu) systems [1]. This process has been also appJied in the binary RE123 and was found that they also exhibit good Tc and large Jc values [2]. We have further extended this process to ternary RE123 systems successfully [3,4]. In this paper we report the Jc-B properties of ternary RE123 composites prepared by the OCMG process.
2. EXPERIMENTAL DETAILS The different rare-earth oxides, BaC0 3 and 0921-4534/97/$17.00 © Elsevier Science B.V. All rights reserved. PH S0921-4534(97)00366-3
CuO were weighed to have a nominal composite of (AO.33Bo.33CO.33)Ba2Cu307.x' where A,B and Care selected from Nd, Sm, Eu and Gd elements. The peritectic temperatures (T) obtained from the DTA p measurements were used to determine the proper heat treatment profile for the OCMG process of different ternary RE 123 systems, the detail of which are described elsewhere [4]. In the present experiments, the melt growth was performed in the mixed gas of 0.1 %02 in Ar. The oxygenated samples were used for the Te and Je measurements using a Quantum Design MPMS- 7 SQUID magnetometer. Magnetization loops are measured at 17K using a 7T superconducting magnet.
3. RESULTS AND DISCUSSION Powder x-ray diffraction results on ternary RE 123 composites clearly show that ternary systems consists mainly of 123 phase with a small amount of second phase [3,4]. SQUID measurements on the oxygenated samples showed that Te (onset) varies between 93-9S.3K in different compositions. Optical microscopy, SEM and EPMA investigations show
504
M. Muralidhar et al. / Physica C 282-287 (1997) 503-504
that in all ternaries, the matrix is 123 and has very uniform mixing of rere-earths [3,4]. Our TEM results also confirmed that the formation of 123 phase is very uniform[5]. Figure 1 shows the magnetic Je curves for the ternary RE123 composites in presence of magnetic field parallel to c-axis. The magnetic Je was estimated according to the extended Bean's critical state model using the following relation Je=(20t1M)/[ a(I-a/3b)] where t1M is in emu/cm3 , a and b (a
Je at relatively higher fields is indicative of improved field induced flux pinning caused by structural variations in the presence of three rare earths with in 123 matrix or Nd substituted regions. The reason behind improved Je is not clear at this juncture and needs detailed investigations which are under progress. 4. CONCLUSIONS The critical current density of the ternary RE123 composites are superior to that of YBCO and NdBCO bulk superconductors. The optimization of the processing conditions and the oxygen content in these materials will lead to further increase of the J e values in high applied magnetic fields.
and the Je is Ncm 2• ACKNOWLEDGMENTS --(0)---
Nd-Su-Gdl23
--4.'-- Nd-Eu-Gd123 --,j.k-- Nd-Sm-Gd123
This work was partially supported by NEDO for the R&D of Indust. Sci. and Tech. Forntier program. One of authors (MM) thanks to the Japanese Science and Technology Agency (STA) for providing the fellowship.
REFERENCE
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B [T] Figure 1. Je-B properties of ternary RE123 composites prepared by OCMG process. From the figure it is clear that all the samples showed anomalous peak effect as observed earlier in Nd123 and Sm123 superconductors prepared by OCMG process [1]. Further, it can also be seen that all the samples showed high Ie in the range of 1Q4 N cm2 at 77K In case of Nd-Eu-Gd123 the Je was found 50, 000 Ncm 2 at 77K and 2T. This Je value seems to be the highest reported so far in the literature at 2T region in the RE123 bulk superconductors. The large
[IJ M. Murakami, N.Sakai, T. Higuchi and S.1. Yoo, Supercond: Sci. Technol. 9, 1015 (1996). [2] T. Saitoh, K Segawa, K Kamada, N. Sakai, S.I.Yoo and M. Murakami, In extended abstract, IntI. Wks. on Superconductivity, June 24-27, Iwate, Japan, 185 (1996). [3]M.Muralidhar, H.S.Chauhan,T.Saitoh, KSegawa, K Kamada and M. Murakami, In extended abstract, Intl. Symp. on Advances in Superconductivity, Sept. 17-20, Bombay, India (1996). [4] M.Muralidhar,H.S.Chauhan,T.Saitoh, K Segawa, K Kamada N. Sakai and M. Murakami, Advances in Superconductivity IX, SpringerVerlag, Japan, (1996), in press. [5] M.Muralidhar,H.S.Chauhan,T.Saitoh, K Segawa, K Kamada and M. Murakami, J. Appl. Phys. (1997), To be communicated.
m
PHYSICA ®
~
ELSEVIER
Physica C 282-287 (1997) 503-504
APPLICATION OF OXYGEN CONTROLLED MELT GROWTH (OCMG) IN TERNARY RE123 SYSTEMS M. Muralidhar", H.S. Chauhan", T. Saitohb, K. Segawab, K. Kamadab and M. Murakami" ·SRL-ISTEC, 1-16-25 Shibaura, Minato-Ku, Tokyo-l05, Japan bIwate Industrial Research Institute, 3-35-2, Iioka-Shinden, Morioka, Iwate-020, Japan The detail investigations on growth and superconducting properties of ternary RE 123 systems have been done employing XRD, TEM, SEM, optical microscopy and DC magnetization techniques. XRD results confirmed that in all these systems the main phase was 123 with inclusions of small amount of second phase. The DTA, TEM, SEM and optical microscopy investigations revealed that even in the presence of three rare-earths the matrix RE123 was very uniform. The SQUID measurements on the post annealed samples showed that superconducting transitions Tc (onset) are in the range of 93-95.3K. The highest Jc value obtained in this series of systems was about
50000 Ncm 2 at 2T.
l.INTRODUCTION The critical current density (J c), in high temperature superconductors, is one of the most important parameter for their practical applications. However, the critical current density of high temperature superconductor suddenly decreases with increasing temperature and magnetic field. The recent developments in oxygen controlled melt growth (OCMG) has overcome this problem and made it possible to fabricate the superconductors with higher and sharp superconducting transitions (Tc) and larger critical current density (JJ in the RE123 (RE: Nd, Sm and Eu) systems [1]. This process has been also appJied in the binary RE123 and was found that they also exhibit good Tc and large Jc values [2]. We have further extended this process to ternary RE123 systems successfully [3,4]. In this paper we report the Jc-B properties of ternary RE123 composites prepared by the OCMG process.
2. EXPERIMENTAL DETAILS The different rare-earth oxides, BaC0 3 and 0921-4534/97/$17.00 © Elsevier Science B.V. All rights reserved. PH S0921-4534(97)00366-3
CuO were weighed to have a nominal composite of (AO.33Bo.33CO.33)Ba2Cu307.x' where A,B and Care selected from Nd, Sm, Eu and Gd elements. The peritectic temperatures (T) obtained from the DTA p measurements were used to determine the proper heat treatment profile for the OCMG process of different ternary RE 123 systems, the detail of which are described elsewhere [4]. In the present experiments, the melt growth was performed in the mixed gas of 0.1 %02 in Ar. The oxygenated samples were used for the Te and Je measurements using a Quantum Design MPMS- 7 SQUID magnetometer. Magnetization loops are measured at 17K using a 7T superconducting magnet.
3. RESULTS AND DISCUSSION Powder x-ray diffraction results on ternary RE 123 composites clearly show that ternary systems consists mainly of 123 phase with a small amount of second phase [3,4]. SQUID measurements on the oxygenated samples showed that Te (onset) varies between 93-9S.3K in different compositions. Optical microscopy, SEM and EPMA investigations show
504
M. Muralidhar et al. / Physica C 282-287 (1997) 503-504
that in all ternaries, the matrix is 123 and has very uniform mixing of rere-earths [3,4]. Our TEM results also confirmed that the formation of 123 phase is very uniform[5]. Figure 1 shows the magnetic Je curves for the ternary RE123 composites in presence of magnetic field parallel to c-axis. The magnetic Je was estimated according to the extended Bean's critical state model using the following relation Je=(20t1M)/[ a(I-a/3b)] where t1M is in emu/cm3 , a and b (a
Je at relatively higher fields is indicative of improved field induced flux pinning caused by structural variations in the presence of three rare earths with in 123 matrix or Nd substituted regions. The reason behind improved Je is not clear at this juncture and needs detailed investigations which are under progress. 4. CONCLUSIONS The critical current density of the ternary RE123 composites are superior to that of YBCO and NdBCO bulk superconductors. The optimization of the processing conditions and the oxygen content in these materials will lead to further increase of the J e values in high applied magnetic fields.
and the Je is Ncm 2• ACKNOWLEDGMENTS --(0)---
Nd-Su-Gdl23
--4.'-- Nd-Eu-Gd123 --,j.k-- Nd-Sm-Gd123
This work was partially supported by NEDO for the R&D of Indust. Sci. and Tech. Forntier program. One of authors (MM) thanks to the Japanese Science and Technology Agency (STA) for providing the fellowship.
REFERENCE
u
.... 1
a
1
2
3
4
6
7
B [T] Figure 1. Je-B properties of ternary RE123 composites prepared by OCMG process. From the figure it is clear that all the samples showed anomalous peak effect as observed earlier in Nd123 and Sm123 superconductors prepared by OCMG process [1]. Further, it can also be seen that all the samples showed high Ie in the range of 1Q4 N cm2 at 77K In case of Nd-Eu-Gd123 the Je was found 50, 000 Ncm 2 at 77K and 2T. This Je value seems to be the highest reported so far in the literature at 2T region in the RE123 bulk superconductors. The large
[IJ M. Murakami, N.Sakai, T. Higuchi and S.1. Yoo, Supercond: Sci. Technol. 9, 1015 (1996). [2] T. Saitoh, K Segawa, K Kamada, N. Sakai, S.I.Yoo and M. Murakami, In extended abstract, IntI. Wks. on Superconductivity, June 24-27, Iwate, Japan, 185 (1996). [3]M.Muralidhar, H.S.Chauhan,T.Saitoh, KSegawa, K Kamada and M. Murakami, In extended abstract, Intl. Symp. on Advances in Superconductivity, Sept. 17-20, Bombay, India (1996). [4] M.Muralidhar,H.S.Chauhan,T.Saitoh, K Segawa, K Kamada N. Sakai and M. Murakami, Advances in Superconductivity IX, SpringerVerlag, Japan, (1996), in press. [5] M.Muralidhar,H.S.Chauhan,T.Saitoh, K Segawa, K Kamada and M. Murakami, J. Appl. Phys. (1997), To be communicated.