Growth and investigation of melt-textured SmBCO in air for preparation of Sm123 seedcrystals

Abstract

For an efficient preparation of SmBCO seeds in high quantity and quality weinvestigated two different ways to manufacture Sm123 grains. Sm123 bulks weregrown by the top-seeded melt-textured growth method. Using MgO seedssingle-grained Sm123 samples with a diameter of 18 mm and a thickness of 10 mmwere obtained. Disc-shaped, large-sized SmBCO grains were prepared along thea–b cleavage plane of the bulks. Subsequently, the material was carefully separated into a large quantity ofabout 2 × 2 × 2 mm3 sized seeds with well-known crystallographic orientation. The results imply the feasibility ofa production of larger SmBCO bulks in a batch process. In a second approach, Sm123 barswere melt-processed by a modified Bridgman method in a vertical furnace. Long barsamples were prepared with typical sizes of 7 mm in diameter and 140 mm in length. Thesintered bars were pulled up across a hot zone of a maximum temperature of1090 °C and a longitudinalthermal gradient of 15 K cm−1. For the translation of the samples different constant pulling rates from 0.3 to5.5 mm h−1 were tested. The microstructure of the samples was investigated by means of polarizedoptical microscopy.