Enhanced Transport Critical Current Density of NiO Nano Particles Added YBCO Superconductors

Siti Nurdalila Abd-Ghani1,a, Hon Kah Wye1,b, Kong Ing2,c,

Roslan Abd-Shukor 3,d and Kong Wei4,e 1School of Engineering Infrastructure Technology, Infrastructure University Kuala Lumpur, Unipark

Suria, Jalan Ikram-Uniten, 43000 Kajang, Selangor, Malaysia

2Department of Mechanical, Materials and Manufacturing Engineering, The University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor, Malaysia

3School of Applied Physics, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia.

4School of Applied Science and Foundation Studies, Infrastructure University Kuala Lumpur, Unipark Suria, Jalan Ikram-Uniten, 43000 Kajang, Selangor, Malaysia

asitinurdalila@yahoo.com, bhonkw@iukl.edu.my, cing.kong@nottingham.edu.my, dras@ukm.my, ekwei@iukl.edu.my (corresponding author)

Keywords: NiO nano particles; YBCO superconductor; transport critical current density

Abstract. The effects of NiO nano particles addition in YBa2Cu3O7-δ (YBCO) superconductors had

been investigated. YBCO superconductor powders were prepared by using high purity oxide

powders via solid state reaction method. 0.01 – 0.05 wt.% of NiO nano particles were added into

YBCO. The critical temperature (Tc) and transport critical current density (Jc) were determined by

using four point probe method. The lattice parameters and morphology of the samples were

characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively.

Tc of YBCO increased from 84 K to 87 K with 0.02 wt.% of NiO nano particles addition. The

addition on NiO nano particles have significantly enhanced transport critical current density of

YBCO by acting as flux pinning centers. YBCO with 0.03 wt.% of NiO nano particles performed

the highest Jc up to 1265 mA/cm2 among the NiO-added samples. However, excessive addition of

NiO nano particles in YBCO caused degradation in Tc and Jc.

Introduction

The discovery of high temperature superconductor (HTS) from the copper oxide based materials

has generated the potential electronics materials under technology development today [1]. Most

applications of superconductivity make use of the special ability of a superconductor to carry

electric current without dissipation.

To improve the quality of HTS material, many researchers have introduced nano particles in

their studies [2,3,4,5,6]. Important fundamental properties such as the critical current density (Jc)

was found to be improved from the fact that grain boundaries act as weak links in limiting the

critical current of high-Tc superconductors [7]. Substitution and addition have been widely used to

improve the critical current density (Jc) [8,9]. Addition of nano-particles has been proven as a very

effective way to enhance flux pinning in HTS. Effects of addition of various elements like Zn, Fe

and NiFe2O4 on HTS have been reported [10,11]. In this work, we study the effects of nano

magnetic particles NiO as flux pinning centers on superconducting and transport properties of

YBCO.

Advanced Materials Research Vol. 895 (2014) pp 105-108Online available since 2014/Feb/13 at www.scientific.net© (2014) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.895.105

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Experimental details

The YBa2Cu3O7-δ (YBCO) superconductor powders were prepared by using high purity powders of

Y2O3, BaCO3 and CuO via solid state reaction method. The mixed powders were ground and

followed by sintering in air at 900 ºC for 48 h with an intermediate grinding. NiO nano particles

(24 nm) with 0.01 to 0.05 wt.% were added to YBCO powders and ground thoroughly. Powders

were then pressed into pellets with 13 mm diameter and 2 mm thickness and sintered at 900 ºC for

24 h. Pure YBCO pellet was prepared for comparison.

The electrical resistance-temperature measurements were carried out by using the four-point

probe technique in conjunction with a CTI cryogenics closed-cycle refrigerator. The pellets were

then cut into bar-shaped. The transport critical current density was measured on bar-shaped samples

from 30 – 77 K using the 1 µV/cm criterion. The X-ray powder diffraction (XRD) patterns of the

samples were recorded using a Siemens D 5000 diffractometer with CuKα radiation. The

microstructures of the samples were also determined by using a Philips XL30 Scanning Electron

Microscope (SEM). The distribution of nano NiO was investigated using Energy-dispersive X-ray

Analysis (EDX).

Results and discussion

Fig.1 shows the x-ray diffraction pattern for YBCO with different amount of nano particles NiO.

All peaks can be indexed to YBCO with orthorhombic crystal structure. The (103) peak is the

strongest peak for all sample. Addition of NiO nano particles does not lead to the variation in

crystal structure. The small amount of nano NiO does not enter the YBCO crystal structure. There

are no significant peaks of NiO nano particles found in XRD patterns. Table 1 summarizes the

results for temperature where the resistance begin to show a sudden drop (Tc-onset), the zero-

resistance temperature (Tc-zero) transport critical current density (Jc) and resistivity at room

temperature (ρ300K).

Fig. 1 X-ray diffraction patterns of YBa2Cu3O7-δ added different amount of nano NiO

Small amount of nano NiO has increased Tc-zero of the samples. The samples with 0.02 wt.%

nano NiO shows the highest Tc-zero at 87 K. The lowest resistivity at room temperature shown by

sample with 0.02 wt.% supports its performance of highest zero resistance temperature. Fig. 2

shows the variation of transport critical current density (Jc) of the YBCO sample temperature from

30 - 77 K. The inset shows Jc at 77 K versus amount of nano NiO. All of the samples show a

2θ (Degree)

Inte

ns

ity

(a

.u.)

106 Solid State Science and Technology IV

decrease in Jc when temperature was increased. This is due to the consequence of thermal flux

creep. Sample with 0.03 wt.% nano NiO exhibit the maximum Jc of 1265 mA/cm2. Overall, NiO

nano particles addition has enhanced the current carrying capacity of YBCO superconductors. This

result is expected as strong interaction can be expected between flux line network and magnetic

texture if the magnetic impurities have the same order magnitude with the flux line network [12].

Table 1. Onset temperature (Tc-onset), the zero-resistance temperature (Tc-zero),

transport critical current density (Jc), resistivity at room temperature (ρ300K)

Fig. 2 Transport critical current density (Jc) versus temperature curves for YBa2Cu3O7-δ-(NiO)x and

transport critical current density at 77 K versus amount of nano NiO addition curve (inset)

Fig. 3 SEM micrographs for (a) pure, (b) 0.01wt.%, (c) 0.02wt.%, (d) 0.03wt.%, (e) 0.04wt.% and

(f) 0.05wt.%

Value of x [wt.%]

Tc-onset

[K] T c-zero

[K] Jc

[mA.cm-2

] ρ300K

×10-5

[ Ωm] 0 91 84 152 2.55

0.01 91 86 283 2.16 0.02 90 87 1069 1.55 0.03 91 86 1265 2.03 0.04 90 86 673 2.25 0.05 91 86 463 2.49

Jc (

mA

.cm

-2)

Jc (

mA

.cm

-2)

T (K)

Amount of Nano NiO (wt.%)

(b) (a) (c)

(f) (e) (d)

Advanced Materials Research Vol. 895 107

Figs. 3(a)-(f) show the SEM micrographs for pure YBCO and samples with nano NiO. SEM of

the sample shows a typical surface of the YBCO samples with pores. Most of the samples showed a

dense microstructure with low porosity. All samples were shown to have grain size roughness of

about 4-6 µm. The red dots represent the distribution of nano NiO. Basically, nano NiO is well-

distributed in YBCO superconductors.

Conclusion

In this work, NiO nano particles acted as effective pinning centers in YBCO which enhance the

superconducting and transport properties. A small amount of nano NiO (~0.03 wt.%) can be

introduced to improve the quality of YBCO superconductors.

Acknowledgement

This research was supported by the Ministry of Higher Education under the Fundamental Research

Grant Scheme FRGS/2/2010/SG/KLIUC/02/1.

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