热电材料参数测量方法的研究

发布时间：2018-05-05 07:55

本文选题：热电材料 + ZT值　；参考：《山东大学》2015年硕士论文

【摘要】：热电效应能够实现热能和电能的直接转换,在废热回收发电、绿色制冷、太空探测器供电等方面具有广泛的应用前景,因此受到了广泛的关注。热电转换效率主要取决于热电优值系数ZT＝s2σT/κ,其中S, σ, κ, T分别为Seebeck系数、电导率、热导率和绝对温度。ZT值越高,热电转换效率越高。目前热电参数的测量和热电转换效率的评估存在一些问题。首先,高温Seebeck系数的测量精度不高,如常用的高温热电参数测试系统(Linseis LSR系列)测量Seebeck系数的精度为7%左右,给热电转换效率的评估带来一定误差；其次,在测量ZT值时,Seebeck系数和电导率使用热电参数测试系统(ZEM、LSR等)沿平行样品表面方向测量,而热导率使用导热系数测试仪(如Netzsch、Linseis、TA等公司的热导率测试设备)沿垂直样品表面方向测量,当材料具有各向异性时也会引起较大的误差。针对上述两个普遍存在的问题,本论文以热电参数的精确测量为研究对象,自主搭建了两套热电参数测量设备,深入研究了影响Seebeck系数测量精度的因素,并尝试开发了一种直接测量热电优值系数ZT的新方法。本论文的主要创新之处如下：一、基于对静态法和动态法的研究,自制了一套Seebeck系数和电阻测量设备,使用自制设备对影响Seebeck系数测量精度的因素进行了研究。发现动态法和静态法可以消除寄生电势的影响。使用静态法测量时,样品温差控制在1±0.SK以内,测量精度最高；控温精度越高,测量精度越高,但是虽然控温精度较差时,测量结果波动大,但是平均值与高控温精度下的测量结果相差不大；有效地进行电磁屏蔽可以提高测量精度。经过对以上因素的研究,改进传统方法,可以将自制设备的Seebeck系数的测量精度提高到1.5%,优于商用仪器7%的精度。使用动态法测量,测量的速度高于静态法,在同样的测试环境下也具有较高的测量精度,小于7.2K/mmin的升温速度变化对Seebeck系数的测量没有大的影响。二、基于非平衡热力学,推导了等温和绝热状态下的热电参数方程组,发现通过测量热学短路和热学开路两种状态下的电导率可以直接获得热电优值系数ZT：σT=σq(1+ZT),其中σT、σq分别代表热学开路和短路下的电导率。基于理论分析的结果,自制了一套热电参数测量设备。但目前该方法的测量误差较大,其可行性以及产生误差的原因需要进一步研究。本论文较为系统地研究了高精度测量热电参数的方法,利用静态法和动态法消除Seebeck系数测量中寄生电势的影响,通过选择合适的测量温差、提高控温精度、增加电磁屏蔽等手段大幅度提高了Seebeck系数的测量精度,并开发了一种直接测量热电优值ZT的新方法。研究结果为热电参数的高精度测量提供了理论支持和技术参考,但由于时间原因,直接测量ZT新方法还未深入地研究,目前测量误差较大,在后续的工作中将对其进行优化。
[Abstract]:Thermoelectric effect can realize the direct conversion of heat energy and electric energy. It has a wide application prospect in waste heat recovery generation, green refrigeration, space detector power supply and so on, so it has been paid more and more attention. The thermoelectric conversion efficiency mainly depends on ZT=s2 蟽 T / 魏, where S, 蟽, 魏 T are Seebeck coefficient, conductivity, thermal conductivity and absolute temperature. The higher the thermoelectric conversion efficiency is, the higher the thermoelectric conversion efficiency is. At present, there are some problems in the measurement of thermoelectric parameters and the evaluation of thermoelectric conversion efficiency. First, the measurement accuracy of high temperature Seebeck coefficient is not high. For example, the measurement accuracy of Seebeck coefficient is about 7%, which brings some error to the evaluation of thermoelectric conversion efficiency. In measuring ZT values, the Seebeck coefficient and conductivity are measured along the parallel surface direction using a thermoelectric parameter measuring system, ZEMN LSR, etc. When the thermal conductivity is measured along the vertical surface of the sample by using a thermal conductivity tester (such as the thermal conductivity testing equipment of Netzschi LinseisTA etc.), the larger error will be caused when the material has anisotropy. Aiming at the two common problems mentioned above, this paper takes the accurate measurement of thermoelectric parameters as the research object, builds two sets of measuring equipment of thermoelectric parameters independently, and deeply studies the factors that affect the precision of Seebeck coefficient measurement. A new method for directly measuring the coefficient of excellent value of thermoelectricity ZT has been developed. The main innovations of this thesis are as follows: firstly, based on the research of static and dynamic methods, a set of Seebeck coefficient and resistance measuring equipment is made, and the factors that affect the precision of Seebeck coefficient measurement are studied by using self-made equipment. It is found that dynamic method and static method can eliminate the influence of parasitic potential. When using static method, the temperature difference of the sample is controlled within 1 卤0.SK, and the measurement accuracy is the highest. The higher the temperature control precision is, the higher the measurement precision is, but although the temperature control accuracy is poor, the measurement results fluctuate greatly. But the average value is not different from the measurement results with high temperature control precision, and the effective electromagnetic shielding can improve the measurement accuracy. Through the study of the above factors and the improvement of the traditional method, the measurement accuracy of the Seebeck coefficient of the self-made equipment can be improved to 1.5%, which is superior to the accuracy of the commercial instrument by 7%. The measuring speed of dynamic method is higher than that of static method, and the measurement precision is higher in the same testing environment. The change of heating speed less than that of 7.2K/mmin has no great influence on the measurement of Seebeck coefficient. Secondly, based on the nonequilibrium thermodynamics, the equations of thermoelectric parameters under isothermal and adiabatic state are derived. It is found that the thermal excellent coefficient ZT: 蟽 T = 蟽 Q 1 ZT can be obtained directly by measuring the conductivity of thermal short circuit and thermal open circuit, where 蟽 T and 蟽 Q represent the conductivity of thermal open circuit and short circuit respectively. Based on the results of theoretical analysis, a set of thermoelectric parameters measurement equipment is made. However, the measurement error of this method is large at present, its feasibility and the cause of the error need to be further studied. In this paper, the methods of high-precision measurement of thermoelectric parameters are studied systematically. The static method and dynamic method are used to eliminate the influence of parasitic potential in the measurement of Seebeck coefficient, and the accuracy of temperature control is improved by selecting appropriate temperature difference. The measurement accuracy of Seebeck coefficient is greatly improved by means of increasing electromagnetic shielding, and a new method for direct measurement of thermoelectric excellent value ZT is developed. The research results provide theoretical support and technical reference for high precision measurement of thermoelectric parameters. However, due to time reasons, the new method of direct measurement of ZT has not been thoroughly studied. At present, the measurement error is large, and it will be optimized in the following work.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB302

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