Tellurium-rich phase in n-type bismuth telluride crystals grown by the Bridgman technique

A detailed study of the presence of the segregated tellurium phase in n-type bismuth telluride grown by the Bridgman technique was done, using two different furnace systems. The results of the crystals grown under different conditions (temperature gradient, thermal coupling) are discussed. It is shown that, depending on the growing conditions, the Te-rich phase can be eliminated and, when this is done, variations of the Seebeck coefficient along the crystal depend on the melt volume rather than on crystal length. Values higher than 250 mu V/K were reached for the Seebeck coefficient in these crystals. (C) 1999 Elsevier Science B.V. All rights reserved.