Papers by Author: Shoji Uchimura

Abstract: A Bi2-xSbxTe3(x=0-1.5) thick film thermoelectric element was fabricated using centrifugal deposition and its Sb content-dependent thermoelectric properties were investigated. When the Sb content was low (x=0.5), two types of fine structure along the direction of the thickness were observed. Pole figure measurements revealed that the vicinity of the film surface was composed of single crystal layers oriented along the c-axis and the vicinity of the interface with the substrate was composed of randomly orientated layers. As the content of Sb increased, the degree of orientation improved, and at x=1.5 the entire film was close to a single crystal. A Bi0.5Sb1.5Te3 thick film showed p-type thermoelectric properties and a thermoelectric power factor of 3.5 ×10-3W/mK2. It was thus demonstrated that centrifugal deposition can be used to fabricate thermoelectric elements with high efficiency.

Abstract: Co-firing of multiple materials results in the formation of internal stress due to the difference in shrinkage behavior. This internal stress causes retardation of sintering, crack formation and/or de-lamination at the interface. To reduce internal stress in layered structures, homogeneous pressing via centrifuge has been attempted. The effect of centrifugal pressing was demonstrated by film sintering, in which crack suppression and void removal by the present process were revealed. Owing to the homogeneous microstructure, the thermal stability of the film was significantly improved.

Abstract: Centrifugal sintering is a novel process for the preparation of thick films. In this process, high gravity such as 104g is applied at high temperatures. Because of the distinctive measure of pressing by the centrifugal force, gradient of pressure arises in the specimen, resulting in the graded porous structure during the progress of sintering. After the sintering, highly densified thick films are obtained. Furthermore, crack formation was suppressed by this process.