Superconductors.ORG has filed a claim with the U.S. Patent and Trademark Office asserting that the compound InSnBa4Tm4Cu6O18+ has a critical superconducting transition temperature (Tc) near 150 Kelvin when the lattice structure forms as a 1234/1212 intergrowth. If confirmed, this would establish a new record for high Tc, eclipsing the old mark of 138K set over 13 years ago.
The 1234/1212 intergrowth structure (shown at left) will not form stoichiometrically.
So an indirect method was employed to identify the compound and support the patent claim.
1. The parent compound InSnBa4Tm3Cu5O16+ was found to have four superconducting phases above 77K (see exhibits 2a & 2b below). They appear as sharp resistive transitions near:
87K (<3% by volume)
91K (<3% by volume)
113K (the majority phase)
150K (<3% by volume)
4. When free (unreacted) Tm and Cu are present in the bulk, they will couple and append the parent 1223/1212 structure with additional Tm-CuO2 planes, creating larger unit cells with roughly equal amounts of 1223 and 1234/1212 structures resulting (see below Exhibit 1b).
5. Excluding the 91K phase (since it is likely the known superconductor Tm-123), there are indeed two remaining minority phases of roughly equal volume: the 87K phase and the 150K phase. Of these two, 87K was found by synthesis and testing to be the Tc of InSnBa4Tm4Cu6O18+ with 1223 structure (see Exhibit 4 below). Ergo, the remaining 1234/1212 structure predicted in item 4 must be the 150K phase.
6. This conclusion is buttressed by the below log graph (Exhibit 5) which shows Tc-vs-planar weight ratio. Extrapolating to the point where the planar weight ratio is 1234/1212 for Tm-CuO2 planes, we arrive within one degree of the observed 150K critical temperature.
Analyzing the characteristics of this material:1. Not only is the planar weight ratio high, but the percentage of total unit cell weight that the PWD layers represent is very high.
RESEARCH NOTE: Tm-copper-oxides have been found to be strongly hygroscopic. All tests should be performed immediately after annealing.
- E. Joe Eck
© 2006 Superconductors.ORG
Patent Pending #US60/809,267
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