Sains Malaysiana 37(3):  223-225 (2008)

Enhanced Critical Current Density in MgB₂ with

Dy₂O₃ Particle Additions

(Peningkatan Ketumpatan Arus Genting dalam MgB₂

dengan Penambahan Zarah Dy₂O₃)

Soo Kien Chen, Abdul Halim Shaari, Kean Pah Lim & Mohd Faisal Mohd Aris

Physics Department, Faculty of Science, Universiti Putra Malaysia,

43400 Serdang, Selangor, Darul Ehsan, Malaysia

Received: 12 Jun 2007 /Accepted: 19 November 2007

ABSTRACT

This paper reports on the effect  of oxide particle Dy₂O₃ additions on the superconducting properties of MgB₂. The polycrystalline samples were prepared by well mixing magnesium and boron elemental powders, followed by heat treatment for in situ reaction in inert gas environment. All the samples showed MgB₂ as the main phase with MgO and DyB₄ as impurities. Magnetization measurements showed that the superconducting transition temperature, T_c remained largely unchanged (37.5 – 38K) even for Dy₂O₃ additions up to 15.0 wt.%. However, the transition curve was broadened in samples with larger amount of additions. The best sample with only 0.5 wt.% Dy₂O₃ additions had a J_c of around a factor of 4 higher compared to the pure sample at 6K(1T). Tem imaging showed the distribution of nano precipitates of DyB₄ and MgO within the grain which may improve the pinning leading to enhancement in critical current density, J_c.

Keywords: MgB₂; critical current density; nano precipitates

ABSTRAK

Kertas ini melaporkan  kesan penambahan serbuk oksida Dy₂O₃  terhadap ciri-ciri kesuperkonduksian MgB₂. Sampel polikristal telah disediakan dengan mencampur serbuk magnesium and boron diikuti dengan rawatan pemanasan bagi menghasilkan tindakbalas in situ dalam persekitaran gas lengai. Semua sampel menunjukkan MgB₂ sebagai fasa dominan dengan kehadiran MgO dan DyB₄ sebagai fasa-fasa ketaktulenan. Pengukuran kemagnetan menunjukkan suhu genting, T_c tidak mengalami perubahan besar (37.5 – 38K) walaupun dengan penambahan Dy₂O₃ sehingga 15.0 wt.%. Walau bagaimanapun, lengkung peralihan suhu genting bertambah luas untuk sampel dengan panambahan serbuk oksida yang tinggi. Sampel yang terbaik dengan hanya penambahan 0.5 wt.% Dy₂O₃ mempunyai J_c pada 6K(1T) sebanyak empat kali ganda lebih tinggi berbanding dengan sampel tulen. Imej tem menunjukkan taburan mendakan DyB₄ dan MgO yang bersaiz nano dalam butiran yang memperbaiki kesan pengepinan dan seterusnya meningkatkan ketumpatan arus genting, J_c.

Kata kunci: MgB₂; ketumpatan arus genting; mendakan nano

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