Effect of growth conditions and compositions on the morphology and stability of the solid-liquid interface of Bi [sbnd]Sr [sbnd]Ca [sbnd]Cu [sbnd]O grown by a floating zone method

Abstract

The effects of growth conditions and a variety of nominal compositions of a feed rod on the crystal growth and the stability of the solid-liquid interface of Bi Sr Ca Cu O oxide was studied by using a floating zone method. A variety of growth morphologies at the solid-liquid interface of an as-grown rod have been observed by a polarised optical microscope. The results showed that a planer solid-liquid interface tended to break down into a cellular interface while increasing the velocity from 0.2 mm/h or deviating from the nominal optimal composition of the feed rod Bi 2.1Sr 1.9Ca 1Cu 2O x. Fe-substitution in Bi-2212 depresses the stability of the solid-liquid interface of Bi Sr Ca Cu O oxide. The size of the single crystals of Bi-2212 in an as-grown rod decreases with the increase of the growth velocity and Fe-substitution. An indispensable condition for growth of large size Bi-2212 single crystals with a thickness more than 0.2 mm along the c-axis is that the solid-liquid interface maintains at a stable planar growth fron in an as-grown rod.