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Continuous Nb3Ge superconducting tape prepared by chemical vapour deposition
Solid State Communications, Vol. 23, pp. 487—488, 1977.
Pergamon Press.
Printed in Great Britain
CONTINUOUS Nb3Ge SUPERCONDUCTING TA1~EPREPARED BY CHEMICAL VAPOUR DEPOSITION V. (~emulko,M. Jergel and D. (~abelka Electrotechnical Institute, Slovak Academy of Sciences, DübravskI cesta, 80932 Bratislava, Czechoslovakia (Received 6 January 1977 by J.L. Olsen) A continuous Nb3Ge superconducting tape made by the chemical vapour deposition has been prepared. The critical currents of 3mm wide tape measured at 4.2 Kin transverse magnetic field 51 are from the region of 26 to 172A with the T~values being 13.1 to 15.2 K. X-ray diffraction analysis revealed the Nb3Ge, NbGe2 and Nb5Ge3 phases. IN A RECENT investigation into the superconducting Nb3Ge the superconductivity being around 23K ~ been discovered. To prepare the Nb3Ge films and layers with high onset of Ta’s several methods such as sputter ing technique [1—6],chemical vapour deposition (CVD) [4, 7—14] and, vacuum co-evaporation (by means of electron-beam melting as well as regular resistive heating) [15, 16] were used. The Nb3Ge with highest T~ onset of 22.9K [2] and 23.2 K [3] was preparedby sputtering technique onto hot substrate. As a static substrate in all cases mentioned above the ceramic or metals of different shapes have been used as for instance quartz, A12O3, sapphire, copper, niobium, molybden, Hastelloy B, etc. The first Nb3Ge prepared by CVD method has been announced by Valueva et al. [7]. The samples were deposited onto Mo-wire at 1100°Cand onto quartz tube walls at 900°Cwith the T~onset 17.5 to 19.0K. Further information concerning the Nb3Ge preparation with In the 20K presented communication we report about Ta’s above may be found in [4,8—14]. continuous CVD method of preparing the superconducting Nb3Ge tape. To prepare the Nb3Ge superconductor the same apparatus with vertical deposition chamber as described previously [17, 18] (in case of superconducting Nb3Sn) has been used. A metallic tape of the stainless-steel type 3mm wide and SOpm thick was used 1as with a substrate. the The speed ratio temperatures of moving tape was 4 m 1000 hC and tape processing 830,920, 1100°C.Several meters of tape at each temperature were prepared. The total length of produced Nb 3Ge tape was of the order of ten meters. The in situ niobium and germanium chlorides were used in the molar ratio 1: 1. The molar ratio of hydrogen to chlorides was 10: 1 and into the reaction mixture 0.07mole hr’ of HG was added. The Nb3Ge layer thickness, critical currents and critical temperatures values were measured, and X.ray and TEM analysis were performed. The dependence of 487
Table 1. Dependence ofNb3Ge layer thickness dand the critical temperatures onset T0 upon the substrate processins’ temperature Tsub and/or the substrate heating current ‘sub
-__________________________________________
Sample No.
Taub
1 2 3 4
830 920 1000 1100
[°C]
~ 3.5 4.0 4.5 5.0
[A]
d [pm]
7, [K]
7.1 7.5 6.8 5.7
13.1 14.1 14.1 15.2
3.0
i
/
/ i:l/’Icl .—~
~
W~ -
‘Cl
-
20
_5.
~
T~2I(
0
0 —
Fig. 1. The dependence of critical currents values I~,I~j and their ratio ‘cI~/’cIupon the substrate tape processing temperature Tsub.
the layer thickness as well as that of the 7’, values upon the substrate processing temperatures may be seen from Table 1. The critical currents values of Nb3Ge tape 3mm wide measured in outside transverse magnetic field 51 at 4.2 K are from the region of 26 to 172 A for magnetic field vector perpendicular to the tape surface and, 92 to
488
CONTINUOUS Nb3Ge SUPERCONDUCTING TAPE
121 A for magnetic field parallel with the tape. Their dependence on the substrate temperature is on diagram of Fig. 1. In this diagram, also the anisotropy of critical currents as we call the ratio I~u/I~iis plotted. A strong dependence of ‘ci as well as that of the critical currents anisotropy may be seen. The X-ray diffraction was performed by means of Philips goniometer on as deposited specimens as well as on deposits which were removed from their substrates and the inside wall of the deposition chamber. The structure of the identified phases was found to be predominantly Nb5Ge3 the rest being Nb3Ge and NbGe2 respec. tively. The thin foils for the TEM analysis were prepared
Vol. 23, No.7
by dissolving the substrate in a solution consisting from 5% H3P04—50% HC1—10% HNO3—35% H20 and the Nb—Ge layer was etched to the required thickness by a solution of HF—HNO3—H20 (1:3:4). The grain size of Nb—Ge layers was not very dependent on the substrate heating temperature and it was from 0.3 to 1.2 pm in all studied specimens. As far as the mechanical properties are concerned, the outside appearance of the preparedtape is glossy and the consistency of deposited Nb—Ge layer and the substrate is a very good one. When bending the tape to the 5 mm dia. there are no visible cracks.
REFERENCES 1. 2.
GAVALER J.R.,Appl. Phys. Lett. 23,480(1973). GAVALER J.R., JANOCKO M.A. & JONES C.K.,J. App!. Phys. 45,3009(1974).
3. 4.
TESTARDI L.R., WERNICK J.H. & ROYER W.A., Solid State Commun. 15, 1 (1974). GAVALER J.R., JM4OCKO M.A., BRAGINSKI A.!. & ROLAND G.W., IEEE Trans. MAG-lI, 172 (1975).
5. 6.
KAMMERDINNER L., WU C.T. & LUO H.L.,J. Low Temp. Phys. 24, 111(1976). CHENCINSKI N. & CADIEU F.L.,J. Low Temp. Phys. 16,507(1974).
7.
VALUEVA N.A., PETRUSEVICH I.V. & NISELSON L.A.,Izv. AN SSSR, Neorgan. Mat. 8,2803 (1972).
8.
WIELAND L.J. & WICKLUND A.W.,Phys. Lett. 49A, 407 (1974).
9.
KAWAMURA H. & TACHIKAWA K.,Phys. Lett. 50A, 29(1974).
10. 11. 12. 13.
BRAGINSKI A.I. & ROLAND G.W.,Appl. Phys. Lett. 25, 762 (1974). NEWKIRK L.R., VALENCIA F.A., GIORGI A.L., SZKLARZ E.G. & WALLACE T.C.,IEEE Trans. MAG-11~221 (1975). NEWKIRK L.R., VALENCIA F.A. & WALLACE T.C.,J. Electrochem. Soc. 123,425(1976). ENGELHARDT JJ. & WEBB G.W., Solid State Commun. 18,837 (1976).
14.
BRAGINSKI A.I., ROLAND G.W. & DANIEL R.M.,Appl. Polymer Symp. No. 29,93 (1976).
15. 16.
SIGSBEE R.A.,Appl. Phys. Lett. 29,211(1976). HALLAK A.B., HAMMOND R.H. & GEBALLE T.H.,Appl. Phys. Lett. 29,314(1976).
17. 18.
~ERNU~KO V.,Kovové materidly (Metallic Materials), 13,647(1975). ~ERNU~KO V., JERGEL M., ~ABELKA D. & CHOVANEC F., Czech. J. Phys. B-26, 1156(1976).
Pergamon Press.
Printed in Great Britain
CONTINUOUS Nb3Ge SUPERCONDUCTING TA1~EPREPARED BY CHEMICAL VAPOUR DEPOSITION V. (~emulko,M. Jergel and D. (~abelka Electrotechnical Institute, Slovak Academy of Sciences, DübravskI cesta, 80932 Bratislava, Czechoslovakia (Received 6 January 1977 by J.L. Olsen) A continuous Nb3Ge superconducting tape made by the chemical vapour deposition has been prepared. The critical currents of 3mm wide tape measured at 4.2 Kin transverse magnetic field 51 are from the region of 26 to 172A with the T~values being 13.1 to 15.2 K. X-ray diffraction analysis revealed the Nb3Ge, NbGe2 and Nb5Ge3 phases. IN A RECENT investigation into the superconducting Nb3Ge the superconductivity being around 23K ~ been discovered. To prepare the Nb3Ge films and layers with high onset of Ta’s several methods such as sputter ing technique [1—6],chemical vapour deposition (CVD) [4, 7—14] and, vacuum co-evaporation (by means of electron-beam melting as well as regular resistive heating) [15, 16] were used. The Nb3Ge with highest T~ onset of 22.9K [2] and 23.2 K [3] was preparedby sputtering technique onto hot substrate. As a static substrate in all cases mentioned above the ceramic or metals of different shapes have been used as for instance quartz, A12O3, sapphire, copper, niobium, molybden, Hastelloy B, etc. The first Nb3Ge prepared by CVD method has been announced by Valueva et al. [7]. The samples were deposited onto Mo-wire at 1100°Cand onto quartz tube walls at 900°Cwith the T~onset 17.5 to 19.0K. Further information concerning the Nb3Ge preparation with In the 20K presented communication we report about Ta’s above may be found in [4,8—14]. continuous CVD method of preparing the superconducting Nb3Ge tape. To prepare the Nb3Ge superconductor the same apparatus with vertical deposition chamber as described previously [17, 18] (in case of superconducting Nb3Sn) has been used. A metallic tape of the stainless-steel type 3mm wide and SOpm thick was used 1as with a substrate. the The speed ratio temperatures of moving tape was 4 m 1000 hC and tape processing 830,920, 1100°C.Several meters of tape at each temperature were prepared. The total length of produced Nb 3Ge tape was of the order of ten meters. The in situ niobium and germanium chlorides were used in the molar ratio 1: 1. The molar ratio of hydrogen to chlorides was 10: 1 and into the reaction mixture 0.07mole hr’ of HG was added. The Nb3Ge layer thickness, critical currents and critical temperatures values were measured, and X.ray and TEM analysis were performed. The dependence of 487
Table 1. Dependence ofNb3Ge layer thickness dand the critical temperatures onset T0 upon the substrate processins’ temperature Tsub and/or the substrate heating current ‘sub
-__________________________________________
Sample No.
Taub
1 2 3 4
830 920 1000 1100
[°C]
~ 3.5 4.0 4.5 5.0
[A]
d [pm]
7, [K]
7.1 7.5 6.8 5.7
13.1 14.1 14.1 15.2
3.0
i
/
/ i:l/’Icl .—~
~
W~ -
‘Cl
-
20
_5.
~
T~2I(
0
0 —
Fig. 1. The dependence of critical currents values I~,I~j and their ratio ‘cI~/’cIupon the substrate tape processing temperature Tsub.
the layer thickness as well as that of the 7’, values upon the substrate processing temperatures may be seen from Table 1. The critical currents values of Nb3Ge tape 3mm wide measured in outside transverse magnetic field 51 at 4.2 K are from the region of 26 to 172 A for magnetic field vector perpendicular to the tape surface and, 92 to
488
CONTINUOUS Nb3Ge SUPERCONDUCTING TAPE
121 A for magnetic field parallel with the tape. Their dependence on the substrate temperature is on diagram of Fig. 1. In this diagram, also the anisotropy of critical currents as we call the ratio I~u/I~iis plotted. A strong dependence of ‘ci as well as that of the critical currents anisotropy may be seen. The X-ray diffraction was performed by means of Philips goniometer on as deposited specimens as well as on deposits which were removed from their substrates and the inside wall of the deposition chamber. The structure of the identified phases was found to be predominantly Nb5Ge3 the rest being Nb3Ge and NbGe2 respec. tively. The thin foils for the TEM analysis were prepared
Vol. 23, No.7
by dissolving the substrate in a solution consisting from 5% H3P04—50% HC1—10% HNO3—35% H20 and the Nb—Ge layer was etched to the required thickness by a solution of HF—HNO3—H20 (1:3:4). The grain size of Nb—Ge layers was not very dependent on the substrate heating temperature and it was from 0.3 to 1.2 pm in all studied specimens. As far as the mechanical properties are concerned, the outside appearance of the preparedtape is glossy and the consistency of deposited Nb—Ge layer and the substrate is a very good one. When bending the tape to the 5 mm dia. there are no visible cracks.
REFERENCES 1. 2.
GAVALER J.R.,Appl. Phys. Lett. 23,480(1973). GAVALER J.R., JANOCKO M.A. & JONES C.K.,J. App!. Phys. 45,3009(1974).
3. 4.
TESTARDI L.R., WERNICK J.H. & ROYER W.A., Solid State Commun. 15, 1 (1974). GAVALER J.R., JM4OCKO M.A., BRAGINSKI A.!. & ROLAND G.W., IEEE Trans. MAG-lI, 172 (1975).
5. 6.
KAMMERDINNER L., WU C.T. & LUO H.L.,J. Low Temp. Phys. 24, 111(1976). CHENCINSKI N. & CADIEU F.L.,J. Low Temp. Phys. 16,507(1974).
7.
VALUEVA N.A., PETRUSEVICH I.V. & NISELSON L.A.,Izv. AN SSSR, Neorgan. Mat. 8,2803 (1972).
8.
WIELAND L.J. & WICKLUND A.W.,Phys. Lett. 49A, 407 (1974).
9.
KAWAMURA H. & TACHIKAWA K.,Phys. Lett. 50A, 29(1974).
10. 11. 12. 13.
BRAGINSKI A.I. & ROLAND G.W.,Appl. Phys. Lett. 25, 762 (1974). NEWKIRK L.R., VALENCIA F.A., GIORGI A.L., SZKLARZ E.G. & WALLACE T.C.,IEEE Trans. MAG-11~221 (1975). NEWKIRK L.R., VALENCIA F.A. & WALLACE T.C.,J. Electrochem. Soc. 123,425(1976). ENGELHARDT JJ. & WEBB G.W., Solid State Commun. 18,837 (1976).
14.
BRAGINSKI A.I., ROLAND G.W. & DANIEL R.M.,Appl. Polymer Symp. No. 29,93 (1976).
15. 16.
SIGSBEE R.A.,Appl. Phys. Lett. 29,211(1976). HALLAK A.B., HAMMOND R.H. & GEBALLE T.H.,Appl. Phys. Lett. 29,314(1976).
17. 18.
~ERNU~KO V.,Kovové materidly (Metallic Materials), 13,647(1975). ~ERNU~KO V., JERGEL M., ~ABELKA D. & CHOVANEC F., Czech. J. Phys. B-26, 1156(1976).