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Effects of thickness on the grain alignment and Jc properties of (Hg0.8Re0.2)Ba2Ca2Cu3Ox superconductor thick films
Physica C 460–462 (2007) 1386–1387 www.elsevier.com/locate/physc
Effects of thickness on the grain alignment and Jc properties of (Hg0.8Re0.2)Ba2Ca2Cu3Ox superconductor thick films M.E. Yakinci *, M.A. Aksan, Y. Balci, S. Altin _ ¨ nu¨ U ¨ niversitesi, Fen Edebiyat Faku¨ltesi, Fizik Bo¨lu¨mu¨, Su¨periletkenlik Arasßtırma Grubu, 44280-Malatya, Turkey Ino Available online 14 April 2007
Abstract (Hg0.8Re0.2)Ba2Ca2Cu3Ox superconducting films of 1–80 lm thickness have been prepared on MgO(1 0 0) substrates using spraying process and post-Hg-vapor annealing. The effects of thickness on the grain alignment and Jc properties have been investigated. The best Tc and Tzero were found to be 131.9 K and 129 K respectively, for 50 lm thick sample. Magnetic properties up to 6 T have been investigated. The calculated critical current density, Jcmag, was found to be 4.8 · 105 A cm 2 at 4.2 K for 50 lm thick sample. 2007 Elsevier B.V. All rights reserved. Keywords: (Hg0.8Re0.2)Ba2Ca2Cu3Ox; Superconducting thick films; Thick film superconductors; Grain alignment
1. Introduction Several groups have recently reported the growth of Hgbased films with thicknesses between 1 and 80 lm [1–3]. Most of these films have showed single phase transition above 120 K with significantly high Jc values. This opens up possibilities for applications of thick films in microelectronic technology. In this work, we have produced HgRe-1223 thick films on MgO(1 0 0) substrates and effect of thickness on the grain alignment and Jc properties have been investigated. 2. Experimental The (HgRe)Ba2Ca2Cu3Ox thick films have been prepared using two step processing method. Firstly, a stoichiometric mixture of Ba2Ca2Cu3Ox and ReO powder was mixed, palletized and annealed at 840 C for 15 h in an O2 flow then pulverized and ground for homogenization and re-pelletized and then heat treated at 935 C for 24 h in a flow of Ar and O2 gas mixture. Secondly, HgO and *
Corresponding author. Tel.: +90 422 3410010; fax: +90 422 3410037. E-mail address: [email protected] (M.E. Yakinci).
0921-4534/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.physc.2007.04.097
Ba2Ca2Cu3Ox were mixed under Ar atmosphere and then mixed with an organic binder. The solution was then sprayed onto the single crystal MgO(1 0 0) substrates and heated as explained in Ref. [2]. The crystal structure,the out-of-plane alignment and X-ray pole-figure (XRDPF) measurements were made with Rigaku Rint 2000 X-ray difractometer. The electrical and magnetization measurements were performed using Cryogenic Q-3398 vibrating sample magnetometer. 3. Results and discussion Beside the optimum heating combination (840 C for 20 h) and optimum filling factor of Hg(ffHg) was found to be 0.77 g cm 3, the thickness and the grain alignment were found to be a crucial factor for HgRe-1223 thick films. Multiphase and disoriented crystal formations were obtained for thicknesses 640 lm, Fig. 1a. After 40 lm thicknesses the grains started to align in c-direction and between 50 and 60 lm the degree of orientation reached to maximum, Fig. 1b. Grains were found highly dense and strongly connected in this range of thickness. However, after 60 lm slightly porous and weakly connected films were obtained. A deviation from the c-axis was also seen.
M.E. Yakinci et al. / Physica C 460–462 (2007) 1386–1387
1387
1.00E+06
Jcmag (A/cm2)
1.00E+05
1.00E+04
1.00E+03
0 2 4 6
1.00E+02
Tesla Tesla Tesla Tesla
1.00E+01 10
20
30
40
50
60
70
80
90
100
Thickness (μm) Fig. 3. Thickness-Jcmag plots of films under various fields.
Fig. 1. XRD plots of (a) 40 lm and (b) 50 lm thick films.
Table 1 Summary of the physical properties of films Sample
Thickness, ±3% (lm)
Tc (K)
Tzero
Jcmag
% Hg1223 phase content
Dw
b
A B C D
40 50 70 90
118.6 131.9 118.8 114.3
111.9 129.1 111.7 106.3
4.74 · 104 4.88 · 105 4.01 · 104 3.64 · 104
77 100 78 64
1.36 0.19 1.41 1.49
0.88 0.07 0.93 0.98
% phase content has been evaluated as (0 0 6)1223 + (0 0 7)1223/(0 0 4)1223 + (0 0 6)1223 + (0 0 7)1223 + (0 0 1 0)1223 peaks.
Fig. 2. (1 1 1) pole-figures of (a) 40 lm and (b) 50 lm thick films.
The degree of c-axis alignment has been estimated from w-scan rocking curves of the (0 0 6) Bragg reflections of each sample. The calculated value of the full width at half maximum (FWHM) of (0 0 6) lines of samples A–D were found in the range of (Dw =) 1.49–0.19 depending on the thickness, which gives an out-of-plane disorientation (b) of the grains between 0.98 and 0.07 indicating a degree of divergence in the c-axis orientation of the films, Table 1. The alignment of the samples also checked by XRD pole-figure experiments. The pole-figure data obtained for (1 1 1) Bragg reflection of samples A and B are shown in Fig. 2a and b, respectively. For sample A, randomly distributed contour lines were observed. But for sample B, pole-figures have four evenly distributed poles and inten-
sity contour was distributed symmetrically around the centre. The pole figure of (1 1 1) reflection of the 50 lm thick film indicated single in-plane epitaxy. We found close relation between the orientation-thickness-Jcmag combination. The critical current density, Jcmag, of the samples were calculated using magnetic hysteresis curves, M–H, of the samples at fields between 0-6 T and Bean’s formula [4]. According to M–H curves, magnetization of the samples increases up to 50 lm and remain almost unchanged between 50 and 60 lm. But, after 60 lm thickness it is started to decrease. Calculated Jcmag values at 10 K vary between 3.64 · 104 and 4.88 · 105 A/cm2 depending on the thickness, Table 1. The variation between the thickness-Jcmag-field is given in Fig. 3. The texture, Tc, Tzero, Dw and b also showed similar peculiarities, Table 1. This indicates that a limit value for thicknesses of the (Hg0.8Re0.2)Ba2Ca2Cu3Ox films which is essential to obtain an optimum results. In general, for the first time, we introduce a Dw–b–Jcmag combination for Hg-1223 thick films in this work. The b value reflects the c-axis grain alignment and is influenced by the thickness. Both b and Dw values differs the Jcmag. It is apparent that b and Dw does not decrease further for thickness above 60 lm and both increases exponentially and Jcmag value of the films was found largely dependant to b and Dw values. Acknowledgement This research was supported by the Scientific and Tech_ ¨ BITAK) nical Research Council of Turkey (TU under Contract No. TBAG-2213 (102T092). References [1] Z.W. Xin, Y.Y. Xie, J.Z. Wu, Physica C 402 (2004) 45. [2] M.E. Yakinci, M.A. Aksan, Y. Balci, Supercond. Sci. Technol. 18 (2005) 494. [3] K. Przybylski, T. Lada, A. Paszewin, Physica C 341 (2000) 543. [4] C.P. Bean, Phys. Rev. Lett. 8 (1962) 250.
Effects of thickness on the grain alignment and Jc properties of (Hg0.8Re0.2)Ba2Ca2Cu3Ox superconductor thick films M.E. Yakinci *, M.A. Aksan, Y. Balci, S. Altin _ ¨ nu¨ U ¨ niversitesi, Fen Edebiyat Faku¨ltesi, Fizik Bo¨lu¨mu¨, Su¨periletkenlik Arasßtırma Grubu, 44280-Malatya, Turkey Ino Available online 14 April 2007
Abstract (Hg0.8Re0.2)Ba2Ca2Cu3Ox superconducting films of 1–80 lm thickness have been prepared on MgO(1 0 0) substrates using spraying process and post-Hg-vapor annealing. The effects of thickness on the grain alignment and Jc properties have been investigated. The best Tc and Tzero were found to be 131.9 K and 129 K respectively, for 50 lm thick sample. Magnetic properties up to 6 T have been investigated. The calculated critical current density, Jcmag, was found to be 4.8 · 105 A cm 2 at 4.2 K for 50 lm thick sample. 2007 Elsevier B.V. All rights reserved. Keywords: (Hg0.8Re0.2)Ba2Ca2Cu3Ox; Superconducting thick films; Thick film superconductors; Grain alignment
1. Introduction Several groups have recently reported the growth of Hgbased films with thicknesses between 1 and 80 lm [1–3]. Most of these films have showed single phase transition above 120 K with significantly high Jc values. This opens up possibilities for applications of thick films in microelectronic technology. In this work, we have produced HgRe-1223 thick films on MgO(1 0 0) substrates and effect of thickness on the grain alignment and Jc properties have been investigated. 2. Experimental The (HgRe)Ba2Ca2Cu3Ox thick films have been prepared using two step processing method. Firstly, a stoichiometric mixture of Ba2Ca2Cu3Ox and ReO powder was mixed, palletized and annealed at 840 C for 15 h in an O2 flow then pulverized and ground for homogenization and re-pelletized and then heat treated at 935 C for 24 h in a flow of Ar and O2 gas mixture. Secondly, HgO and *
Corresponding author. Tel.: +90 422 3410010; fax: +90 422 3410037. E-mail address: [email protected] (M.E. Yakinci).
0921-4534/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.physc.2007.04.097
Ba2Ca2Cu3Ox were mixed under Ar atmosphere and then mixed with an organic binder. The solution was then sprayed onto the single crystal MgO(1 0 0) substrates and heated as explained in Ref. [2]. The crystal structure,the out-of-plane alignment and X-ray pole-figure (XRDPF) measurements were made with Rigaku Rint 2000 X-ray difractometer. The electrical and magnetization measurements were performed using Cryogenic Q-3398 vibrating sample magnetometer. 3. Results and discussion Beside the optimum heating combination (840 C for 20 h) and optimum filling factor of Hg(ffHg) was found to be 0.77 g cm 3, the thickness and the grain alignment were found to be a crucial factor for HgRe-1223 thick films. Multiphase and disoriented crystal formations were obtained for thicknesses 640 lm, Fig. 1a. After 40 lm thicknesses the grains started to align in c-direction and between 50 and 60 lm the degree of orientation reached to maximum, Fig. 1b. Grains were found highly dense and strongly connected in this range of thickness. However, after 60 lm slightly porous and weakly connected films were obtained. A deviation from the c-axis was also seen.
M.E. Yakinci et al. / Physica C 460–462 (2007) 1386–1387
1387
1.00E+06
Jcmag (A/cm2)
1.00E+05
1.00E+04
1.00E+03
0 2 4 6
1.00E+02
Tesla Tesla Tesla Tesla
1.00E+01 10
20
30
40
50
60
70
80
90
100
Thickness (μm) Fig. 3. Thickness-Jcmag plots of films under various fields.
Fig. 1. XRD plots of (a) 40 lm and (b) 50 lm thick films.
Table 1 Summary of the physical properties of films Sample
Thickness, ±3% (lm)
Tc (K)
Tzero
Jcmag
% Hg1223 phase content
Dw
b
A B C D
40 50 70 90
118.6 131.9 118.8 114.3
111.9 129.1 111.7 106.3
4.74 · 104 4.88 · 105 4.01 · 104 3.64 · 104
77 100 78 64
1.36 0.19 1.41 1.49
0.88 0.07 0.93 0.98
% phase content has been evaluated as (0 0 6)1223 + (0 0 7)1223/(0 0 4)1223 + (0 0 6)1223 + (0 0 7)1223 + (0 0 1 0)1223 peaks.
Fig. 2. (1 1 1) pole-figures of (a) 40 lm and (b) 50 lm thick films.
The degree of c-axis alignment has been estimated from w-scan rocking curves of the (0 0 6) Bragg reflections of each sample. The calculated value of the full width at half maximum (FWHM) of (0 0 6) lines of samples A–D were found in the range of (Dw =) 1.49–0.19 depending on the thickness, which gives an out-of-plane disorientation (b) of the grains between 0.98 and 0.07 indicating a degree of divergence in the c-axis orientation of the films, Table 1. The alignment of the samples also checked by XRD pole-figure experiments. The pole-figure data obtained for (1 1 1) Bragg reflection of samples A and B are shown in Fig. 2a and b, respectively. For sample A, randomly distributed contour lines were observed. But for sample B, pole-figures have four evenly distributed poles and inten-
sity contour was distributed symmetrically around the centre. The pole figure of (1 1 1) reflection of the 50 lm thick film indicated single in-plane epitaxy. We found close relation between the orientation-thickness-Jcmag combination. The critical current density, Jcmag, of the samples were calculated using magnetic hysteresis curves, M–H, of the samples at fields between 0-6 T and Bean’s formula [4]. According to M–H curves, magnetization of the samples increases up to 50 lm and remain almost unchanged between 50 and 60 lm. But, after 60 lm thickness it is started to decrease. Calculated Jcmag values at 10 K vary between 3.64 · 104 and 4.88 · 105 A/cm2 depending on the thickness, Table 1. The variation between the thickness-Jcmag-field is given in Fig. 3. The texture, Tc, Tzero, Dw and b also showed similar peculiarities, Table 1. This indicates that a limit value for thicknesses of the (Hg0.8Re0.2)Ba2Ca2Cu3Ox films which is essential to obtain an optimum results. In general, for the first time, we introduce a Dw–b–Jcmag combination for Hg-1223 thick films in this work. The b value reflects the c-axis grain alignment and is influenced by the thickness. Both b and Dw values differs the Jcmag. It is apparent that b and Dw does not decrease further for thickness above 60 lm and both increases exponentially and Jcmag value of the films was found largely dependant to b and Dw values. Acknowledgement This research was supported by the Scientific and Tech_ ¨ BITAK) nical Research Council of Turkey (TU under Contract No. TBAG-2213 (102T092). References [1] Z.W. Xin, Y.Y. Xie, J.Z. Wu, Physica C 402 (2004) 45. [2] M.E. Yakinci, M.A. Aksan, Y. Balci, Supercond. Sci. Technol. 18 (2005) 494. [3] K. Przybylski, T. Lada, A. Paszewin, Physica C 341 (2000) 543. [4] C.P. Bean, Phys. Rev. Lett. 8 (1962) 250.