A fundamental pinning mechanism has been identified in the Bi-Sr-Ca-Cu-0 system. The pinning strength has been greatly increased by the introduction of calciumand copper-rich precipitates into the sample matrix. The calcium and copper werc supersaturated in the system by complete melting, and the fine calcium and copper particles precipitated during subsequent crystallization anneal to obtain the superconducting phases. The intragrain critical current density has been increased from the order of 10~A/cm~t o 10 A/cm at 5 T. The corresponding pinning mechanisms are discussed.
Effect of substrate temperature and biasing on the formation of 110 K BiSrCaCuO superconducting single target sputtered thin films AIP Conf.Kinetics of the 110 K superconducting phase formation has been studied in the Bi-Sr-Ca-Cu-O system with and without the addition of small amounts of lead. The kinetics of the phase transformation has been greatly affected by lead doping. The time required for the maximum formation of the 110 K phase is substantially reduced by the addition of lead. This phenomenon has been shown to be associated with the lead enhancing the nucleation and growth process of the 110 K phase and the diffusivity of calcium and copper.
Recent experiments have indicated that a torque transducer can be constructed based on local bands of naturally stabilized remanent circumferential magnetization within a hollow steel shaft. A strong coercive force along with the crystalline anisotropy combine to stabilize the circumferential magnetization of the sensing area of the shaft. A torqued shaft has its magnetic axis tilted into a helical orientation, which generates an axial field signal linearly proportional to the applied torque that can be sensed externally to the shaft. Our research has shown that the transducer function can be improved by appropriate sequential heat treatments in a helium atmosphere. Subsequent to all heat treatment steps, the test shafts were measured to determine the changes in axial and circumferential magnetic hysteresis properties and to track the development of the magnetic sensing area to applied torque ͑sensitivity͒. Although little change was produced in the originally narrow axial hysteresis loops, a 10%-20% decrease was observed in both axial coercive force and remanent magnetization, and correspondingly, a 50% increase was observed in sensitivity, accompanied by a higher linear saturation limit. Additionally, the heat treatment cycle significantly widened the originally broad circumferential hysteresis loops, resulting in a substantial increase in circumferential coercive force, which improves the stability of the sensory region.
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