New Si-Ge Materials for Generators of Cosmic Use
New Highly Effective Thermoelectric Materials Based on Hard Silicon-Germanium Solution for Generators of Cosmic Use
Tech Area / Field
- MAT-ALL/High Performance Metals and Alloys/Materials
- NNE-MEC/Miscellaneous Energy Conversion/Non-Nuclear Energy
3 Approved without Funding
Sukhumi Institute of Physics and Technology, Georgia, Tbilisi
- South Dakota School of Mines and Technology, USA, SD, Rapid City
Project summaryThe aim of the Project is to develop new highly effective thermoelectric materials on the basis of hard Silicon-Germanium solution and study their properties.
Another aim of the Project is to investigate thermic stability of the worked out multicomponent materials within thermobatteries in the conditions close to exploitation and on the basis of the obtained data to prognose energetic characteristics and terms of service of thermoelectric generators (TEG) for cosmic use.
At present all over the world the works on the development of cosmic space are carried out. New cosmic devices are designed and launched. New type orbital planetary asteroid scientific stations, sondes and selfgoing devices to observe the surfaces of celestial bodies are constructed. In many already existing and perspective cosmic projects thermoelectric Nuclear Energetic Plants (NEP) are considered to be the source of autonomous energy feed of device. The main element of such plant is thermoelectric generator based on hard solution Si-Ge system alloys. According to thermoelectric, physico-chemical and mechanical properties these alloys prevail over all the rest already known high temperature thermoelectric materials. Future of cosmic energetics is with them.
The obtained analysis show that the efficiency of the materials based on hard solutions of Si-Ge system p- and n-types which are being used today in thermoelectric generators at temperature 1000 K do not exceed 0.62×10-3 K-1 and 0.8×10-3 K-1 respectively.
Actuality of the problem is the following. The demands connected with the increase of power density, efficiency and resource of thermoelectric generators of current put forward the problem of further increase of Q-factor and stability of materials based on hard solutions of Si-Ge system.
New and unique approach suggested in the Project is based on the fact that essential increase of efficiency of Si-Ge alloys p- and n- types is reached by accurate dosed alloying with multicomponent dopes and their crystallization processing on modern plant of Czochralski type in more balanced conditions, than at zone melting. Also the evaluation of energetic and exploitation possibilities of the obtained alloys is done on the basis of testing in the composition of basic element TEG – thermoelectric batteries (TB) on specially worked out methodics.
Scientific value of the Project in the case of its fulfillment is the following:
– data on the mechanism and kinetics of phase transformations of multicomponent systems on Si-Ge basis will be obtained;
– data about the influence on phase composition and degree of homogeneity of alloys on alloying level and conditions of crystallization will be obtained;
– influence of annealing in temperature gradient on distribution of basic and alloying components along p- and n- branches of TB will be studied;
– methods of accelerated resource tests of TB will be worked out and service prolongation terms of the obtained Si-Ge alloys on the basis of new methods will be prognosed.
Practical value of the Project. There will be obtained new alloys p- and n-types S0.8Ge0.2 composition efficiency of which at temperature 970 K is (0.92-0.94)×10-3 K-1 and (0.95-0.98)×10-3 K-1 respectively and at 1,000 K efficiency ~ 1×10-3 K-1 is expected.
While using these alloys energetic characteristics of TEG will essentially increase. Maximal efficiency will reach 10% at temperatures of hot and cold junctions equal to 1,270 K and 570 K, respectively, which is 25% higher than those of TEGs based on existing alloys. (Mass gabarite characteristics of NEP will not be changed, which is very important while launching cosmic devices).
Economic Profit of the Project. Definite part of the works connected with principle possibility of obtaining highly effective Ge-Si alloys has been already fulfilled. The rest part of the work forseen by the Project is going to be realised with quite not big financing compared with the established ones in the world practice for solving analogous scientific technological problems.
If using the obtained alloys in TEGs in NEP in order to solve the energy problems of cosmic devices of different types, economic interest will be very attractive.
The Project corresponds to the goals and problems of ISTC as it will be fulfilled by coworkers of one of the wellknown Institutes of Military Industrial complexes of the former USSR.
Participants of the Project are scientists and highly qualified specialists who have great experience of work in the corresponding to the Project field of activity. Financing of the Project has great human importance for these workers. Being refugees from Sukhumi their social position is very difficult.
Potential role of international collaborators is in exchange of information while fulfilling the Project and using the obtained results to solve the problems of cosmic energetics.