• 20% Cu doping MgB2 raise Tc to 49K, and Tc0 = 45.6 K
– (Sun Y P, Song W H, Wen H H, et al. Superconductivity at 49 K in copper doping magnesium diboride[Z]. 2001.)
MgB2
The temperature dependences of the normalized resistivity ρ(T)/ρ(300 K)for the samples of MgB2, Mg0.98Ca0.02B2 and Mg0.92Ca0.08B2.
Sun Y, Yu D, Liu Z, et al. Structural and superconducting properties of Ca-doped MgB2 superconductors[J]. Superconductor Science and Technology. 2007, 20(3): 261.
– (Vajpayee A, Awana V P S, Balamurugan S, et al. Effect of PVA doping on flux pinning in bulk MgB2[J]. Physica C: Superconductivity. 2007, 466(1–2): 46-50.)
prepared by: luokan
Contents
• Structure of some typical metal borides • Properties and application of some metal
borides
– MgB2 – ZrB2 – CaB6 …
• Conclusion
Metal Borides: Structure and Performance
Carenco S, Portehault D, Boissière C, et al. Nanoscaled Metal Borides and Phosphides: Recent Developments and Perspectives[J]. Chemical Reviews. 2013, 113(10): 7981-8065.
MgB2
• Its superconductivity was discovered by the group of Akimitsu in 2001. Its critical temperature (Tc) of 39 K is the highest amongst conventional superconductors. This material was first synthesized and its structure confirmed in 1953 but its superconducting properties were not discovered until 2001.
• Two types of doping to improve the superconductivity of MgB2
– Mg1-xMxB2(Al, Be, Ca, Cu, Li, Na, Zn…) – MgB2-yXy(Be, C, N, O…)
பைடு நூலகம் MgB2
• Various means of doping MgB2 with carbon can improve the upper critical field and the maximum current density, 5% doping with carbon can raise Hc2 from 16 T to 36 T whilst lowering Tc only from 39 K to 34 K
Metal Borides
• Boron is a chemical element with symbol B and atomic number 5
• Boron (B) naturally occurs in two isotopes, 10B and 11B, the latter of which makes up about 80% of natural boron
• Boron can form a metal boride with almost all metals at high temperatures
• Metal Borides(MmBn) tend to form interstitial compouds,
Boron polymorphs
β-rhombohedral boron
Metal Borides
Metal Borides
Metal Borides
One single cell of YB66
Metal Borides
MgB2
Magnesium diboride (MgB2) is a simple ionic binary compound that has proven to be an inexpensive and useful superconducting material. Density 2.57 g/cm3 Melting point 830℃
α-boron
Density(g/cm3) 2.46
Vickers Hardness(GPa)
42
Bulk Modulus(GPa)
185
Bandgap(eV) 2
β-boron
2.35
45
224
1.6
Liu G, Niu P, Yin L, et al. α-Sulfur Crystals as a Visible-Light-Active Photocatalyst[J]. Journal of the American Chemical Society. 2012, 134(22): 9070-9073.