Frustrations Of A Ceramicist - The Scientist - Magazine of the Life Sciences
Abstract
While nuclear magnetic resonance (NMR) equipment represents the biggest market for superconductivity technology, more than 60% of the current technology is applied there, the flurry of activity in the new high-temperature superconductors has not yet translated to state-of-the art changes in NMR. In fact, researchers face three major hurdles in the race to realize the potential of these promising ceramics. For most of the past 15 months, attention has centered on YBa2Cu3O7 usually referred to as "1-2-3," a ceramic that becomes superconducting below 93 K. Exciting as the research has been, the material poses considerable impediments to commercial users. First, 1-2-3 in most bulk samples has a relatively low capacity to carry current (critical current density). It is difficult to create and, perhaps worst of all, shows low strength and little ductility. The low critical current density comes from a phenomenon known as “weak-link” behavior. In a polycrystalline sample, individual grains or single crystals are superconducting with a relatively high critical current density, more than a million amps per cm2. But the grain boundary creates a barrier to the transport of supercurrent. Much of the present processing research looks toward eliminating weak-link behavior, and the first step has