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Physical Property Characterization of Bulk MgB2 Superconductor | | V.P.S. Awana
; Arpita Vajpaye
; Monika Mudgel
; H. Kishan
; V. Ganesan
; A.M. Awasthi
; G. L. Bhalla
; | | Date: |
8 Jul 2008 | | Abstract: | We report synthesis, structure/micro-structure, resistivity under magnetic
field [R(T)H], Raman spectra, thermoelectric power S(T), thermal conductivity
K(T), and magnetization of ambient pressure argon annealed polycrystalline bulk
samples of MgB2, processed under identical conditions. The compound
crystallizes in hexagonal structure with space group P6/mmm. Transmission
electron microscopy (TEM) reveals electron micrographs showing various types of
defect features along with the presence of 3-4nm thick amorphous layers forming
the grain boundaries of otherwise crystalline MgB2. Raman spectra of the
compound at room temperature exhibited characteristic phonon peak at 600 cm-1.
Superconductivity is observed at 37.2K by magnetic susceptibility C(T),
resistivity R(T), thermoelectric power S(T), and thermal conductivity K(T)
measurements. The power law fitting of R(T) give rise to Debye temperature at
1400K which is found consistent with the theoretical fitting of S(T),
exhibiting ThetaD of 1410K and carrier density of 3.81x 1028/m3. Thermal
conductivity K(T) shows a jump at 38K, i.e., at Tc, which was missing in some
earlier reports. Critical current density (Jc) of up to 105 A/cm2 in 1-2T
(Tesla) fields at temperatures (T) of up to 10K is seen from magnetization
measurements. The irreversibility field, defined as the field related to
merging of M(H) loops is found to be 78, 68 and 42 kOe at 4, 10 and 20K
respectively. The superconducting performance parameters viz. irreversibility
field (Hirr) and critical current density Jc(H) of the studied MgB2 are
improved profoundly with addition of nano-SiC and nano-Diamond. The physical
property parameters measured for polycrystalline MgB2 are compared with earlier
reports and a consolidated insight of various physical properties is presented. | | Source: | arXiv, 0807.1203 | | Services: | Forum | Review | PDF | Favorites | |
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