Comparative Study on AC Susceptibility of YBa2Cu3O7−δ Added with BaZrO3 Nanoparticles Prepared via Solid-State and Co-Precipitation Method

Nurhidayah Mohd Hapipi,Soo Chen,Masato Murakami,Kean Lim,Oon Lee,Jee Lim,Muralidhar Miryala,Kar Tan,Mohd Awang Kechik,Abdul Shaari

doi:10.3390/cryst9120655

Nurhidayah Mohd Hapipi, Soo Chen + Show 8 more

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https://doi.org/10.3390/cryst9120655

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Abstract

Polycrystalline samples of YBa2Cu3O7−δ (Y-123) added with x mol% of BaZrO3 (BZO) nanoparticles (x = 0.0, 2.0, 5.0, and 7.0) were synthesized using co-precipitation (COP) and solid-state (SS) method. X-ray diffraction (XRD) patterns showed the formation of Y-123 and Y-211 as the major and minor phases, respectively. The samples prepared using COP method showed higher weight percentage of Y-123 phase (≤98%) compared to the SS samples (≤93%). A peak corresponding to BZO was also found in the samples added with BZO nanoparticles. The increasing intensity of the BZO peak as the BZO amount increased showed the increasing amount of the unreacted nanoparticles in the samples. Refinement of unit cell lattice parameters indicated that all the samples have an orthorhombic crystal structure and there is no orthorhombic-tetragonal phase transformation. As observed using scanning electron microscopy (SEM), all the samples showed randomly distributed grains with irregular shape. The average grain size for the pure sample prepared using COP method is smaller (0.30 µm) compared with that of the pure SS sample (1.24 µm). Addition of 7.0 mol% BZO led to an increase of average grain size to 0.50 μm and 2.71 μm for the COP and SS samples, respectively, indicating grain growth. AC susceptibility (ACS) measurement showed a decrease in the onset critical temperature, Tc-onset with BZO addition. Comparatively, Tc-onset for the COP samples is higher than that of the SS samples. The value of Josephson’s current, Io increased up to 2.0 mol% BZO addition, above which the Io decreased more drastically for the SS samples. The value of Io is 53.95 μA and 32.08 μA for the 2.0 mol% BZO added SS and COP samples, respectively. The decrease of Io is attributed to the distribution of BZO particles at the grain boundaries as also reflected in the drastic decrease of phase lock-in temperature, Tcj. As a result of smaller average grain size, the presence of more grain boundaries containing insulating BZO particles led to lower Io in the COP samples.

Highlights

Yttrium-barium-copper-oxide, YBCO is the first type-II high temperature superconductor (HTS)that has been discovered to be superconducting above the boiling point of liquid nitrogen
Pure samples (x = 0.0) were prepared according to the same procedure to serve as reference for the purpose of comparison
The X-ray diffraction (XRD) patterns were indexed to Y-123 phase with orthorhombic crystal structure and space group Pmmm (ICSD: 01-078-2143)

Summary

Introduction

Yttrium-barium-copper-oxide, YBCO is the first type-II high temperature superconductor (HTS)that has been discovered to be superconducting above the boiling point of liquid nitrogen. In order for Y-123 to be more feasible for a wide range of applications, numerous studies have been undertaken to improve its critical temperature, Tc and critical current density, Jc [1,2,3]. In this regard, addition of chemical dopants is one of the most straight forward strategies. It was shown that the addition of BaZrO3 (BZO) nanoparticles into Y-123 improved Jc without affecting much the Tc value [4,5] This is because BZO did not dope into the structure of Y-123. They either remained unreacted within the matrix or reacted with Y-123 to form nano-precipitates leading to enhanced flux pinning [6]

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