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A7: Developments in measurement techniques and preparation methods
For the wide application of thermoelectric (TE) conversion technology, many TE device fabrication processes have been proposed. We have also proposed ink-jet printing technique. In this technique, developed thermoelectric inks (TE ink) of p- and n-type Bi-Te are printed on a glass substrate using commercial ink-jet printer. After the printing, the device is sintered in a rapid-annealing furnace. It is important to clarify the change of thermoelectric properties by the sintering process. In particular, thermal conductivity change is important. In this study, we have measured thermal conductivity of sintered or as-dried sample using 3ω method.
Experimental procedure (sample preparation and setup) is as follows.
(1) Thin sensor wire of Al was fabricated on a glass substrate by vacuum evaporation method.
(2) An insulating SiNx layer was deposited on the sensor wire.
(3) Sample of p-type (Bi1-xSbx)2Te3 ink was dropped on an Al block using a micropipette.
(4) The sample was dried in vacuum for 1 hour and sintered at 400 ˚C, 7 min., in Ar atmosphere.
(5) The sample was put on and pressed against the sensor wire.
Thermal conductivity measurement of sintered or as-dried samples carried out using 3ω measurement system and two heat flow model [1]. Evaluated thermal conductivity κsample of as-dried samples are 0.2-0.3 WK-1m-1. On the other hand, sintered samples show κsample = 0.4-0.7 WK-1m-1. These higher κsample is attributed to the growth of nanoparticle size and the removal of capping agent. We will present detail of experimental and discussion.
[1] S. Nishino, M. Koyano, K. Suekuni, and K. Ohdaira, J. Electron. Mater. (2014), DOI: 10.1007/s11664-014-2993-9.