Study of intermetallic compounds isostructural to MgB2

R. L. Meng, B. Lorenz, J. Cmaidalka, Y. S. Wang, Y. Y. Sun, J. Lenzi, J. K. Meen, Y. Y. Xue, C. W. Chu

Research output: Contribution to journalConference articlepeer-review

15 Citations (Scopus)


The small intergrain effect of MgB2 on supercurrent makes it one of the most promising candidates for superconducting conductors due to its easier processing and the associated lower manufacturing cost. Unfortunately, the superconducting transition temperature Tc is only 40 K. However, band-structure calculations predict that a higher Tc than that of MgB2 is possible for isostructural and isovalent intermetallic compounds with greater lattice parameters or greater unit cell volumes. The prediction appears to be consistent with the negative pressure effect on Tc observed. The substitution of the larger Ca-ions for the smaller Mg-ions has thus been suggested to raise Tc, but not yet realized. Alternatively, we have synthesized and studied a series of binary and pseudobinary intermetallic compounds, AGa2, AGa2-xSix, and AAl2-xSix, where A = Ca, Sr, or Ba, which are isostructural to MgB2 and have greater lattice parameters than MgB2. In spite of the greater lattice parameters, AGa2 are not superconducting. However, all pseudobinary compounds AGa2-xSi2 and AAl2-xSi2 for 0.6 < x < 1.5 are superconducting. Superconductivity is reported for the first time in SrAlSi, with Tc of 5.1 K. Although Tc varies with x in a similar fashion for all members of the series, no specific correlation between Tc and lattice parameters or ionic mass is observed. The maximum Tc of these compound series with different A's varies between 5.5 and 7.8 K, much lower than that of MgB2. The results strongly suggest the unique role of B in the superconductivity of C32 intermetallic compounds. They also demonstrate that factors additional to the lattice parameters and densities of states must play an important role, and that the rigid-band model is not sufficient to account for the observations.

Original languageEnglish
Pages (from-to)3042-3046
Number of pages5
JournalIEEE Transactions on Applied Superconductivity
Issue number2 III
Publication statusPublished - 2003 Jun
Event2002 Applied Superconductivity Conference - Houston, TX, United States
Duration: 2002 Aug 42002 Aug 9

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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