| The thermoelectric effect refers to conversion between electricity and thermal. With a wide range of applications in the waste heat recovery, green refrigeration, supplying electricity for space probes and other aspects, it received widespread attention. Thermoelectric conversion efficiency depends on the thermoelectric figure of merit ZT=S2σT/(/) with S, σ,κ, T, refering Seebeck, electrical conductivity, thermal conductivity and absolute temperature. The higher accuracy of temperature control, the higher the ZT value, the higher the thermoelectric conversion efficiency. At present, there are some problems in the measurement of thermoelectric parameters and the assessment of thermoelectric conversion efficiency. First of all,Seebeck coefficient measurement accuracy under high temperature is not very high,for instance, the Seebeck coefficient measurement accuracy of the Linseis LSR series device is 7%. Secondly, when measuring ZT, the measurement direction of Seebeck and electrical resistivity is different from the measurement direction of Thermal conductivity. There will be large error when the material has anisotropy.In response to the above two common problems, we study the high accuracy measurement of thermoelectric parameters in this paper and make two thermoelectric parameters measurement devices to study several elements’impacts on the measurement of thermoelectric parameters measurement. On the other hand, we try to create a new method to measure the ZT directly. The main innovation of this paper is as follows:Firstly, Make a Seebeck and resistance measurement device based on static and dynamic methods. Expand research on several elements including contact potential, temperature difference across the sample, the changing rate of temperature, the temperature stability, electromagnetic interference. Study their impacts on the measurement of Seebeck. We find that dynamic and static method can eliminate the influence of contact potential. Under static method, we can get a highest Seebeck coefficient measurement accuracy when the temperature difference across the sample is within 1±0.5K; the higher accuracy of temperature control, the higher accuracy of the Seebeck measurement accuracy; Electromagnetic shielding can effectively improve the Seebeck measurement accuracy. After optimizing the device with the research results, the Seebeck measurement accuracy is 1.5% which is lower than 7%. Under dynamic method, we can also get a good measurement accuracy if the experiment condition is the same. The measurement speed of dynamic method is higher than static method. A measurement speed lower than 7.2K/min does not make a great effect on the Seebeck measurement.Secondly, based on non-equilibrium thermodynamics, we get thermoelectric parameter equations under isothermal state and adiabatic state. ZT can be derived from the electrical conductivity under these two states.σT=σq(1+ZT), with σT、σq referring electrical conductivity under isothermal state and adiabatic state. Make a thermoelectric parameters measurement device based on the theory. By now, the measurement error of the method is big and we should do a further reaearch to find explanations.This paper systematically studied the high-precision measurement methods of thermoelectric parameters. The static and dynamic Seebeck coefficient measurement method can eliminate the influence of parasitic potential. We can increase the measurement accuracy of Seebeck coefficient significantly by selecting the appropriate temperature difference, improving temperature control accuracy, adding electromagnetic shielding. We develop a new method for the direct measurement of the thermoelectric figure of merit ZT.The results provide theoretical support and technical reference for the high-precision measurement of thermoelectric parameters. But due to time reasons, we can not study the new method in depth, so the ZT measurement error is large. The follow-up work will optimize it. |
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