LOW-TEMPERATURE ELECTROCHEMISTRY ON HIGH T(C) SUPERCONDUCTORS

The charge transfer across superconductor/ionic conductor interfaces represents a relatively new experimental and theoretical field. This paper deals with electrochemical studies in this area. Both n-type classical superconductor (SC) and p- and n-type high T(c) superconductors (HTSCs) in contact with different superionic conductors (Ag beta"-alumina, Ag+ ion conducting glass, and RbAg4I5) which are used as solid electrolytes (SE) are considered in experiments covering the temperature range 10K less-than-or-equal-to T less-than-or-equal-to 298K. The Faradaic process occurring at HTSC/SE interfaces in the silver deposition and dissolution, measured by either a transient technique in the time domain or by electrochemical impedance spectroscopy (EIS) in the frequency domain. The results show a positive admittance peak in transient measurements or a corresponding negative impedance peak in EIS measurements at T almost-equal-to T(c). These findings are attributed to an enhancement of the rate of the Faradaic reaction around T(c). The effect is interpreted as a quantum-electrochemical phenomenon caused by the contribution of Cooper pairs crossing the electrochemical double layer as correlated charge carriers and participating in the charge transfer step of the phase boundary reaction. A proximity-like phenomenon can be excluded.