Current Issues in the Solid State Chemistry of High T_c Superconductors

Abstract

I discuss a few of what I believe to be open questions in the solid state chemistry of high T_c superconductors. Topics include: standards for the announcement of the discovery of a “new” superconductor, two-phase vs. solid solution behavior in (La, Sr)₂CuO₄, (Nd, Ce)₂CuO₄, and Ba₂YCu₃O_7-δ, universal curves of T_c vs. x, and, briefly, the doping mechanism in “Bi₂Sr₂CaCu₂O_8+δ”, and very high T_c superconductors and metastable or difficult to synthesize phases.