Mg Difüzyonu Tekniği ile Türkiye’de Saflaştırılmış Bor Kullanılarak Üretilen MgB2 için B Saflığının Süperiletkenlik Özellikleri Üzerine Etkisi

Öz

MgB₂ süperiletken külçeleri, Türkiye’de saflaştırılmış olan üç farklı saflıkta B tozu kullanarak tümüyle aynı koşullarda Mg difüzyon yöntemiyle sentezlendi. Laboratuvar ölçekli çalışmalarda çoğunlukla yüksek saflıkta başlangıç tozları kullanılmaktadır. Büyük ölçekli üretim için yüksek saflıktaki başlangıç tozları üretim maliyeti açısından büyük bir yük getirmektedir. Bu çalışmamızda Mg difüzyon yöntemi için B düşük saflık derecesinin etkisi incelenmiştir. 850 °C’de 10 saatlik ısıl işlem sonucu üretilen MgB₂ külçe numunelerinin, mikro yapısal özellikleri XRD analizleri ile incelenmiştir. XRD sonuçları Rietveld yöntemiyle arıtılarak örgü parametreleri a=b=3,08 Å, c=3,52 Å civarında elde edilmiştir. Kristal boyutları ve mikro gerinimleri Scherrer ve Williamson-Hall formülleri kullanılarak hesaplanmıştır. Ayrıca manyetik özellikleri incelendiğinde, %86,70 saflıkta B kaynağı kullanılan numune de T_c değeri 38,74 K ve 20 K’de J_c(B=0) değeri ise 3,14x10⁵ A/cm² olarak tespit edilmiştir. Manyetik ölçümlerden F_p hesaplanmış ve çivilenme mekanizmaları Dew-Hughes'un ölçeklendirme yaklaşımı ile irdelenmiştir. Numunelerimizin tümünde baskın çivilenme mekanizması tane sınırları ve süperiletken olmayan nokta çivilenme mekanizmaları olduğu tespit edilmiştir. İlgili teknolojiler için önemli olan yüksek J_c ve T_c değerlerine %86,70 saflıkta Türkiye’de saflaştırılmış olan B kaynağı ile ulaşılabileceği gösterilmiştir.

Anahtar Kelimeler

• MgB2
• B Saflığı
• Rietveld Arıtımı
• Kritik Akım Yoğunluğu
• Çivilenme Mekanizması

Effect of B purity on MgB2 superconductor prepared by Mg diffusion technique using Turkish Boron

Öz

MgB₂bulks were synthesized by the Mg diffusion method under exactly the same conditions, using B powder of three different purities purified in Turkey. In laboratory scale studies, high purity starting powders are used. For large-scale production, low purity powders are better in terms of production costs. In this study, the effect of low purity grade B on the Mg diffusion method was examined. The microstructural properties of MgB₂ samples produced by heat treatment at 850 °C for 10 hours were examined by XRD analysis. Rietveld refinement was performed on these results, and lattice parameters were obtained around a=b=3.08 Å, c=3.52 Å. Crystal sizes and microstrains were calculated using the Scherrer and Williamson-Hall formulas. In addition, by magnetic measurements, the T_c was determined to be 38.74 K, and the J_c (B = 0) at 20 K was determined to be 3.14x10⁵ A/cm² for the sample using an 86.70% purity B source. F_p was calculated, and pinning mechanisms were examined using the Dew-Hughes scaling approach. The dominant pinning mechanism was determined to be grain boundaries and non-superconducting points. It has been shown that high J_c and T_c values, which are important for relevant technologies, can be achieved with the 86.70% purity of the B source purified in Turkey.

Anahtar Kelimeler

• MgB2
• B purity
• Rietveld purification
• critical current density

Kaynakça

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