| Abstract | The Polaris high intensity, medium resolution, time-of-flight neutron diffractometer at ISIS has been used in a real-time study to observe phase evolution in rods of melt-cast Bi1.6Pb0.4Sr2Ca3Cu4Oy in situ as they were recrystallized by passage of a dc current under a series of controlled atmospheres. Together with simultaneous measurement of current and resistance to facilitate control over sample heating, the experiment required visual monitoring of the sample during neutron diffraction data collection. This article describes the apparatus constructed to carry out these experiments, along with the necessary modifications made to Polaris and its control systems, and presents results which demonstrate the effectiveness of the technique. The results presented show that the initial appearance of the Bi-2201 phase occurred before hot zone formation. On formation of the hot zone, development of Bi-2212 took place at the expense of Bi-2201. Finally, passage of the zone saw the Bi-2212 redissolve and Bi-2201 reform. ©1998 American Institute of Physics. |
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