| Yazarlar |
Prof. Dr. Özgür ÖZTÜRK
Kastamonu Üniversitesi, Türkiye |
Doç. Dr. Elif AŞIKUZUN TOKEŞER
Kastamonu Üniversitesi, Türkiye |
Öğr. Gör. Şeydanur KAYA
Kastamonu Üniversitesi, Türkiye |
Nevin Soylu Koç
Bolu Abant İzzet Baysal Üniversitesi, Türkiye |
|
Murat Erdem
Türkiye |
| Özet |
| MgB2 samples are produced by ex situ reaction method under vacuum, and various (0, 10, 20 Bar) Ar pressure for 0.5 and 1 h. The effect of ambient pressure and annealing duration on the microstructure and electrical properties of bulk samples are investigated. XRD, SEM, and magnetoresistance measurements are made. The a and c lattice parameters and the grain size values are the highest for the samples produced under vacuum and their values decrease with increasing Ar pressure. Moreover, these values increase when the annealing duration increases from 0.5 to 1 h. The increasing pressure reduces the bond lengths between the atoms thus the grain sizes decrease. Smaller grain size promotes the connection between grains which results in an increase of the critical current density (Jc). SEM micrographs reveal that the produced samples have granular structure which is a characteristic feature of MgB2. The decrease of grain sizes and thus enhancement in grain connectivity with increasing pressure is also confirmed by SEM images. Magneto resistivity measurements show that Tc values of the samples produced under vacuum are the highest. Tc values decrease with increasing ambient pressure and applied magnetic field. The activation energies (U0) of the samples are calculated using Arrhenius plots due to thermally activated flux flow theory. Existence and increase of Ar pressure causes increase of activation energies. The samples produced with 0.5-h annealing have higher activation energies than the ones produced with 1-h annealing. |
| Anahtar Kelimeler |
| Activation energy | Magnetoresistivity | MgB 2 | Superconductivity |
| Makale Türü | Özgün Makale |
| Makale Alt Türü | SSCI, AHCI, SCI, SCI-Exp dergilerinde yayımlanan tam makale |
| Dergi Adı | Journal of Superconductivity and Novel Magnetism |
| Dergi ISSN | 1557-1939 |
| Dergi Tarandığı Indeksler | SCI-Expanded |
| Makale Dili | İngilizce |
| Basım Tarihi | 05-2017 |
