Growth and investigation of melt-textured SmBCO in air for preparation of Sml23 seed crystals

摘要

For an efficient preparation of SmBCO seeds in high quantity and quality we investigated two different ways to manufacture Sml23 grains. Sml23 bulks were grown by the top-seeded melt-textured growth method. Using MgO seeds single-grained Sml23 samples with a diameter of 18 mm and a thickness of 10 mm were obtained. Disc-shaped, large-sized SmBCO grains were prepared along the a-b cleavage plane of the bulks. Subsequently, the material was carefully separated into a large quantity of about 2X2X2 mm3 sized seeds with well-known crystallographic orientation. The results imply the feasibility of a production of larger SmBCO bulks in a batch process. In a second approach, Sml23 bars were melt-processed by a modified Bridgman method in a vertical furnace. Long bar samples were prepared with typical sizes of 7 mm in diameter and 140 mm in length. The sintered bars were pulled up across a hot zone of a maximum temperature of 1090 deg C and a longitudinal thermal gradient of 15 K cm~(-1). For the translation of the samples different constant pulling rates from 0.3 to 5.5 mm h~(-1) were tested. The microstructure of the samples was investigated by means of polarized optical microscopy.