Title :
Highly textured NaxCoO2-δ ceramics fabricated by tape casting
Author :
Itahara, H. ; Fujita, K. ; Sugiyama, J. ; Tsukada, T. ; Tani, T.
Author_Institution :
Toyota Central R&D Labs. Inc., Aichi, Japan
Abstract :
Highly textured NaCoO2-δ (NCO) ceramics with improved thermoelectric properties have been prepared by tape casting. NCO platelets with 5 - 10 μm in diameter and 5 in aspect ratio were synthesized by a co-precipitation method and used as starting materials. The NCO platelets were well mixed with Na2CO3 particles and binder, tape-cast by a doctor-blade technique, dewaxed at 1073 K and then sintered with a uniaxial pressure in air. In particular, we investigated the effects of preparation conditions on thermoelectric properties; that is, 1) the mixing ratio of NCO and Na2CO3 particle, 2) composition of NCO platelets, and 3) the sintering temperature. As a result, highly c-axis aligned specimens were obtained; the maximum c-axis orientation degree (f) was estimated as 0.942 by a Lotgering´s method. Also, the NCO specimen with the maximum Na content exhibited the highest power factor (1.44 mWm-1K-2 at 1050 K) in the direction of the preferred {001} plane.
Keywords :
ceramics; cobalt compounds; precipitation; sodium compounds; tape casting; texture; thermoelectricity; 1050 K; 1073 K; 5 to 10 micron; Lotgering´s method; NaxCoO2-δ; co-precipitation method; composition; doctor-blade technique; highly textured NaxCoO2-δ ceramics; maximum c-axis orientation degree; mixing ratio; power factor; preparation conditions; sintered; sintering temperature; starting materials; tape casting; thermoelectric properties; uniaxial pressure; Ceramics; Ethanol; Plasma measurements; Plasma temperature; Powders; Scanning electron microscopy; Shape measurement; Tape casting; Temperature distribution; X-ray scattering;
Conference_Titel :
Thermoelectrics, 2003 Twenty-Second International Conference on - ICT
Print_ISBN :
0-7803-8301-X
DOI :
10.1109/ICT.2003.1287486
