Zintl phases form a large family of compounds whose electronic conform to 8-N or Zintl – Klemm concept. This class of materials has been identified as promising for thermoelectric applications. For the last time the problem of energy transmission to the long distances has been very acute and therefore development of new materials became topical. One of new class materials for utilization as high-temperature thermoelectric materials with Zintl bonding( Zintl phase) that employ the pnictides of rare earth elements and have the Yb14MnSb11 structure type.Yb14MnSb11, Yb14MnBi11, and Eu14MnSb11 compounds are considered to be Zintl phases and have unique properties and have generated new scientific ideas, have been obtained from ytterbium and europium pnictides. These compounds have high melting temperatures and their magnetic properties change from paramagnetism to ferromagnetism. Efficiency of these materials for conversion of thermal energy into electrical depends on the dimensionless figure of merit zT, where zT = S2T/rk, , and S = Seebeck coefficient, r = electrical resistivity, and k = thermal conductivity. All these three parameters are interconnected and it is necessary to modify one of them, for example Seebeck coefficient can be increased by the pressure including chemical in order to obtain the maximum value zT. So when antimony is partially replaced by tellurium, zT coefficient if of great interest to develop the effective methods of synthesis to obtain compact samples and characterize the new Zintl phases.
High-temperature thermoelectric materials are becoming increasingly useful for applications such as power generation of deep space probes, sea buoys and remote telecommunications. Thermoelectric devices are considered environmentally- benign - power sources that could provide part of the solution to today’s energy problem. Thermoelectric generators convert thermal energy directly into electrical energy, require little to no fuel, minimal maintenance and can be designed to operate over a large temperature range (300-1275K).
Therefore ,synthesis, crystals growth, characterization of new thermoelectrical materials is important endeavor.
The main of the project will be synthesis, growing single crystals substance, investigated new Zintl phase based on pnictides of rare earth metals, the study of their chemical and physical properties as well as applications as high-temperature thermoelectric materials for energy generation from waste heat sources.
New materials were found by building new phase diagrams, emphasizing new Zintl phases, investigating their thermal, magnetic, electrical properties to develop new technique, particularly to transfer energy to long distances.
Status in the sphere of investigations in the Institute of Chemistry AS RT:
1. All phase diagrams of Ln-Sb, Ln-Bi systems excluding Eu-Bi systems, have been studied.2. Eu-Mn-Sb, Eu-Mn-Bi, Yb-Mn-Sb, Yb-Mn-Bi subsystems have been studied and the number of new, triple non-organic compounds which can be considered the new Zintl phase, have been obtained.3. Monocrystals Yb14MnSb11 and its solid solutions with composition Yb14-х LnxMnSb11 , where Ln- Gd,Dy,Tb, Er,Ho,Tm, Lu and Yb14MnSb11-xTex, have been obtained and investigated.
Effect of suggested project on the progress in this sphere.
As we know, issue of thermal energy transformation into electrical, its transmission to the long distances is one of the most important goals of science and engineering. As a result of synthesis of new materials that promote to solve this issue, makes its contributions to the progress of this sphere. This type of transformation of thermal energy into electrical is ecologically clean method. Besides, the obtained material will be of scientific value expanding knowledge of interesting class of non-organic compounds formed by electropositive elements and elements with Zintl bonding.
The competence of project participants of the specified area.
The project will be carried in Institute of Chemistry by V.I.Nikitina AS of Republic of Tajikistan ,where for more than 40 years they are engaged in synthesis, reception of powders and crystals of new compounds of rare earth elements .
Makhmudov F., manager of project, young scientist is expect in the synthesis and crystals grown of refractory materials: Catherine A. Uvarov, M.N.Abdusalyamova, F.Makhmudov, Kurt Star, Jean-Pierre Fleurial and Susan M. Kauzlarich. “ The Effect of Tm Substitution on the Themoelectric Perfomenc of Yb14MnSb11”. Science of Advanced Materials, 2011,v.3,p.652-658. Tanghong Yi,1 Peter Klavins,2 M. N. Abdusalyamova,3Makhmudov F,3 Susan M. Kauzlarich Magnetic and transport properties of Te doped Yb14MnSb11 Journal of Materials Chemistry , 2012,22,14378-14384 He worked projects T-1597, T-1882(ISTC).
Professor, Dr. Abdusalyamova M.,scientific lead of project, is an authority in the field of rare-earth elements chemistry. She has published more than 300 research papers and 3 monographers, worked in project T-1597, T-1598 T-1882(ISTC). M.N.Abdusalyamova. “Phase diagrams and thermodynamic properties of rare earth-antimony systems”. Journal of. Alloy and Compound., 1993,v.202,p.L15. M.N.Abdusalyamova, O.I.Rachmatov et.al. “Phase diagrams and thermodynamic properties of rare earth-bismuth systems”. Journal of Alloys and Compounds, 1996, v.240,p.272. ( M.N.Abdusalyamova, O.I.Rachmatov. Preparation and investigation of rare earth pnictides at the Institute of Chemistry of the Tajik Academy of Sciences”, PartI, ELEMENTS, March 1998, N3,p.5. M.N.Abdusalyamova, O.I.Rachmatov. “The terbium-bismuth system”. Z.Naturforsh.,2002, v.57a,p.101. Professor, Dr Vasiliyva is expert in the field of physic-chemical analysis and worked in project T-1597(ISTC). M.N.Abdusalyamova, I.G.Vasilyeva. “ Phase equilibrium and intermediate phase in the Eu-Sb system”, Journal of Solid State Chemistry, 2011, v.184, p.2751-2755.
Expected results and their application.
In the result of the works new materials with high zT will be obtained to transform thermal energy into electrical and to transmit them to long distances. Building of new triple phase diagrams, doping of Yb14MnSb11, Yb14MnBi11, Eu14MnSb11, Eu14MnBi11 will contribute to the development of technological process of these materials considering minimal negative effect made on humans, animals and environment
Project correspondence to ISTC goals.
Scientists (more than 50 %) who earlier have been engaged in development of rocket materials and technologies within the limits of the State programs of the USSR will assist in the project implementation of the project will give opportunities of their activity reorientation on peace researches and provide them with workplaces.During the project implementation previous contacts with leading Science Centers of the Europe, USA, Canada, Japan that are engaged with researches in the field of rare earth elements will be adjusted and continued. It will promote integration of scientists of Tajikistan into the international scientific community and introduction of modern techniques in industry of Tajikistan
Role of Foreign Collaborators/Partners
Forms of collaboration with foreign collaborators: Joined researches Transmission of samples for study
Interchange of information in the process of project implementation Joined working seminars, consultations. Execution of joined publications Partnership in received materials commercialize
Technical Approach and Methodology
Technical approach and methodology of project implementation is based on unique combination of experimental devices and professional level of the project participants both in the sphere of physic-chemical analysis and technological sphere. Advanced methods and methodology will be applied for investigation process.
