International Conference on Thermoelectrics, July 6-10, 2014

30.04.2014

Crystal Ltd. plans to take part in The 2014 International Conference on Thermoelectrics in Nashville, USA.

In the course of conference young scientists of Crystal Ltd. will report on the subject:

Structural and dimensional specifications of spinning powders p-Bi_0,5Sb_1,5Te₃ , compacted with hot vacuum moulding and spark plasma sintering

Recently thermoelectricity has generated increasing interest as alternative conversion technique of thermal energy to electric energy and conversely.

Increasing scope of thermoelectric materials occurs due to enlarging dimensionless quantity of thermoelectric figure of merit ZT equals:

ZT = (α²σ /κ )T, where:

α is Seebeck coefficient, V/K

σ  is specific electrical conductivity, Om^-1m^-1

κ is specific thermal conductivity, Vt m^-1K^-1

T is temperature of material, K.

Scientific research oriented to enlarging of thermoelectric figure of merit is under way on optimization of used compositions of materials and technologies (normally directional crystallization, hot vacuum moulding, extrusion), as well as on search of new materials (clathrates, hard cobalt ores, nanomaterials) and technologies (melt spinning, spark plasma sintering).

Melt spinning is advanced technology of material’s preparation, based on flash cooling of melt, applied mostly for production of solders and amorphous alloys in metallurgy. Technology consists in feed of melt on water-cooled or liquid-nitrogen-cooled drum and production of it constituting light-gauge crystallized tapes or powder. Structural characteristics and sizes of crystal grain of processed material differ from material crystallized under equilibrium condition due to speeds of  material’s chilling may work up to 10⁴–10⁷ (K/с).

For the first time melt spinning production of thermoelectric material was reported a few years ago.  Materials with thermoelectric figure of merit ZT up to 1,5 were produced  in the conducted workings. Recently data ZT of spinning materials up to 1,3 has been confirmed by research of Crystal Ltd.

Powders of thermoelectric material p-Bi_0,5Sb_1,5Te₃ by melt spinning were produced, their structural characteristics were explored. Samples were prepared by the methods of hot vacuum moulding and spark plasma sintering from powders, their thermoelectric characteristics were explored within the temperature range at 100 to 700 К (100 – 700 К). It is shown that samples prepared by the methods mentioned above have low thermal conductivity, keeping values of the electrical conductivity and Seebeck coefficient comparable with traditional crystallized materials thereby thermoelectric figure of merit ZT reaches the value equals 1,05 – 1,15 at 330 – 350 К.

These characteristics of material will allow essentially raising operational characteristics of semiconductors - thermoelectric modules or Peltier modules. Thermoelectric module in its turn is active cooling element of Peltier module-based thermoelectric conditioner. Production of thermoelectric material with value ZT = 1,3 will allow essentially raising refrigerating capacity of such units as:

Thermoelectric assembly air-to-air

Thermoelectric assembly air-to-liquid

Thermoelectric assembly air-to-contact.