Wide dynamic range current‐voltage characterization system for ceramic superconductors

Transport current‐voltage (I‐V) characteristics gathered over several orders of magnitude of current can reveal much about the loss mechanisms in high T c superconductors. This article describes the design and implementation of a novel, computer‐controlled, I‐V characterization system which permits a I‐V curve spanning five orders of magnitude of current to be captured in 50 ms. The advantages of this system over other methods of obtaining I‐V curves are discussed. The system is applied to the study of high T c superconductors and preliminary measurements are presented. Data obtained at 77 K for polycrystalline YBa2Cu3O7−δ are shown to be consistent with a I‐V relation of the form, V=k(I−I c ) n , where I c is the critical current, and k and n are constants.