M. S. Rogachev

Current state of thermoelectric material science and the search for new effective materials

The reasons for the recent increased interest in thermoelectricity are considered. Modern thermoelectric materials for practical use are reviewed. Criteria to be met by effective thermoelectric materials are analyzed. It is shown that the solid-solution method has almost completely exhausted itself. Directions in the search for new thermoelectric material classes are analyzed. The development of new bulk thermoelectric materials is connected with the search for and design of materials in which the peculiarities of the structure determine the strong scattering of phonons and decrease in thermal conductivity while maintaining high transport properties of charge carriers. The concept ‘phonon glass–electron crystal’ is of practical interest. Scientific and technological advances over the last decade give hope that more effective thermoelectric materials will be developed in the nearest future. One of the perspective applications of new thermoelectric materials is connected with the development of thermoelectric generators with segmented thermoelectric elements.

Prospects of creating efficient thermoelectric materials based on the achievements of nanotechnology

The elaboration of low-dimensional thermoelectric structures has been shown to allow an increase in the efficiency of thermoelectric materials by the end of the 20th century. The achievements in nanotechnology open up new opportunities in searching for prospective thermoelectric materials and structures. The physical aspects in the creation of low-dimensional thermoelectric structures have been reviewed. The capabilities of developing technologies for the synthesis of thermoelectric structures on the basis of superlattices, quantum wires, and quantum dots have been analyzed. The methods of fabrication and advances in the elaboration of nanocomposite thermoelectric materials have been discussed. The problems in the production of second-generation nanocomposites and their possible solutions have been considered. The methods for diagnosing low-dimensional thermoelectric structures are presented, as well.

Investigation of thermal linear expansion for nanostructured Si0.8Ge0.2P0.022 in wide temperature range

The results of investigation of thermal linear expansion for high temperature thermoelectric material nanostructured Si0.8Ge0.2P0.022 n-type with maximum thermoelectric figure of merit Z = 0.98 10-3 K are presented. Investigations were carried out by dilatometric method in the temperature range from 300 to 1220 K in dynamic heating and cooling regimes with using of infrared radiation source. Temperature dependence of thermal linear expansion coefficient (TLEC) was analyzed. The average value of TLEC for Si0.8Ge0.2P0.022 was determined, which is equal to ~5.910-6 K-1.

Mo/Ni and Ni/Ta–W–N/Ni thin-film contact layers for (Bi,Sb)2Te3-based intermediate-temperature thermoelectric elements

We have examined the possibility of utilizing thin-film contact layers for producing reliable Ohmic contacts to proposed intermediate-temperature (Bi,Sb)2Te3-based thermoelectric materials with improved thermoelectric properties, which allow the working temperature range to be extended to 600 K. Three contact configurations have been produced by ion-plasma magnetron sputtering: a single Ni layer, Mo/Ni bilayer, and Ni/Ta–W–N/Ni three-layer system. It has been shown that reliable contacts can be produced using Mo/Ni and Ni/Ta–W–N/Ni layers, which prevent interdiffusion between the materials to be joined and ensure good adhesion to the thermoelectric element.

Performance of Bi2Te3 Thermoelectric Element Improved by Means of Contact System Ni/Ta-W-N/Ni

In this paper the materials with improved thermoelectric properties developed based on Bi2Te3 were used for the production of thermoelectric generator. It allowed to extend the operating temperature range of the material to 550 K. Bi2.0Te2.4Se0.6 doped with 0.12 wt% CuBr (dimensionless coefficient ZT = 1.1 at a temperature of 450–550 K) was used as a material for manufacturing n-type branches. Bi0.4Sb1.6Te3.0 doped with 0.12 wt% PbCl2 and 1.5 wt% Te (dimensionless coefficient ZT = 1.2 at a temperature of 450–550 K) was used as a material for manufacturing p-type branches. The following materials were used as the contact system: 100 nm layer of nickel as the ohmic contact layer; 100 nm layer of amorphous alloy Ta-W-N as a diffusion barrier layer; and 400 nm layer of nickel as a wetting layer for soldering. Study of adhesion of this contact system demonstrated good quality. The breakout force was 12 MPa.

Investigation and Calibration Methods of Precise Temperature Sensors for Controlling Heat Consumption

Authors developed precise temperature sensor with wireless interface (WTS). Methods of thermocompensation and individual calibration of WTS were developed in order to provide high requirements of the temperature measurement accuracy (0.02 °C). Measuring hardware-software complexes for the realization of this methods and carrying investigations were also developed.

Electronic thermometer with the data transfer by radiochannel

Precise electronic thermometer (ET) with the data transfer by radio channel is developed. Original patented design, circuitry and program solutions are employed in ET. Measuring hardware-software complexes for the investigation and calibration of ET are developed on the basis of the National Instruments equipment with using of LabView software.

Hardware and software equipment for the complex investigation of the wireless smart transducers

Hardware and software equipment for the complex investigation of the wireless smart transducers used in the systems for controlling thermodynamic parameters of energy carries was developed on the basis of National Instruments equipment. Stand tests and qualify transducers by the parameters of radio channel and power supply simulating real conditions of exploitation. Software on the development environment of LabView is developed for automation of investigation and testing processes. Stand can be operatively rearranged by appropriate adjustments, which allows testing following wireless standards: ZigBee, WiFi, WiMAX, Bluetooth, etc.

Intelligent system and electron components for controlling individual heat consumption

An intelligent system and its electron components are developed that implement an innovative method for measuring individual heat consumption. For the intelligent system and its electron components, original design-technological, circuit, hardware, and software solutions are proposed. The methods and mathematical models for evaluating individual heat consumption are developed and validated.

Investigation of Nanostructured Thermoelectric Material Si0.8Ge0.2P0.022 for Application in Multisectional Legs of Thermoelectric Elements

Complex investigations of high-temperature thermoelectric material nanostructured Si0.8Ge0.2P0.022 ntype were carried out. Temperature dependencies of conductivity, thermoelectric coefficient and thermal conductivity were studied. Obtained data were used for the calculation of temperature dependence of ZT. Maximum value of ZT  1.04 is observed at 900 °C. Differential scanning calorimetry indicates on the high thermal stability of the nanostructured material. It was established that optimal temperature range for the application of the material in the multisectional legs of thermoelements is 600-900 °C.