Study of orientation in polycrystalline Bismuth telluride alloys

Abstract

It is well known that sintered samples of Bi₂Te₃ and its alloys have an apparent electrical conductivity that is highest perpendicular to the direction of pressing. However, measurements of electrical resistance do not indicate whether this is due to preferred orientation of the grains or to the formation of aligned cracks. Studies of sintered material have, therefore, been made using an X-ray reflection technique and, also, measurements of the Seebeck coefficient in the region of mixed-conduction. Preferred orientation has been found throughout hot-pressed samples, but in cold-pressed material such orientation has either been absent or confined to the surface layers. It is concluded that hot-pressing is preferable to cold-pressing in the production of sintered thermoelements.