High temperature layer superconducting cuprates (HTLSC) alloys: (Bi1.7Pb0.3Sr2Can-1CunO2n+4+δ)2,n=1-9 called (2s:2:n-1:n) prepared in Uzbekistan from melts in concentrated sun flux, followed by rapid cooling, SFQA technology that preserves melt tiling by confinement of conduction layer: |(CuO2)1/2|Ca|(CuO2)1/2]n-1| in the hard shell ||, of the n=1 phase,[(CuO2)1/2|SrO|Bi1.7Pb0.3O|Bi1.7Pb0.3O|SrO|(CuO2)1/2]2. Disproportion leads to different n-phase mixing, and periodic lattice distortions (PLD) through bond resonance covalent crystalaxes: 2(rCu+2+rO-2)=4.2Å>a=3.82Å>d(CuO)+2-3/2d(O3))=3.2Å≈(cn-c1)/2(n-1). Individual phase local bonds Cu-Ca, Cu-Sr, Cu-O-Cu are ascertained by X-Ray diffraction near Cu K-edgefollowed by Cu-Ca bond scattering. The HTLSC density, ρ decrease as n increases obtains Tc,n ~180 K, identified due to n=8 phase on the surface of bulk n=4. Thus, bond resonanceleads to higher n phases on surface and predicts: Tc,n ⇒298K as n⇒50, if the superconducting skin depth is within c50, of a few μm even in mixed n phases.
J. Kmiec, K. Tyson, Juana Acrivos, D. Gulamova, and J. Chigvinadze. "Covalent bonds in superconducting rapid cooled alloys: (Bi1.7Pb0.3Sr2Can‐1CunO2n+4+δ)2, n=1 to 9 detected by local atomic enhanced XRD" Mills College (2012).