Standards Development

Scope

This International Standard specifies the measurement methods for the electronic transport properties of bulk-type thermoelectric materials at high temperature. The measurement methods cover the simultaneous determination of Seebeck coefficient and electrical conductivity of bulk-type thermoelectric materials in a temperature range from 300 K to 1200 K. The measurement methods are applicable to bulk-type thermoelectric materials used for power generation, energy harvesting, cooling, heating, etc.

Purpose

Thermoelectric generators are devices that convert temperature differences into electrical energy. Although thermoelectric phenomena have been used for cooling applications quite extensively, electricity generation has only seen very limited market in niche applications and it is only in recent years that interest has increased regarding new applications of energy generation through thermoelectric harvesting. Thermoelectric generators are gaining popularity as an upcoming clean and green technology, as they convert waste heat into electrical energy.

The performance of thermoelectric material is characterized by dimensionless figure of merit, ZT (= S2T/k, where S is the Seebeck coefficient, is the electrical conductivity, k is the thermal conductivity at a given absolute temperature T). These parameters are determined by the details of the electronic structure and scattering of charge carriers (electrons or holes), and thus are not independently controllable. The power factor, S2 is the key to achieving high performance and energy conversion efficiency. However, there is a trade-off relation between Seebeck coefficient and electrical conductivity according to carrier density. Therefore, simultaneous measurement of Seebeck coefficient and electrical conductivity is required to obtain accurate and reliable power factor. Off-axis 4-point method is used to simultaneously measure Seebeck coefficient and electrical conductivity of bulk-type thermoelectric material, using one measurement system. Using Off-axis 4-point method, reliable and accurate power factor can be measured by reducing the measurement errors of Seebeck coefficient and electrical conductivity. Moreover, measurements of Seebeck coefficient at high temperature are often subject to irreproducibility and inconsistency in results due to a lack of standardized guidelines for measurement procedure. Therefore, measurement method for Seebeck coefficient of bulk-type materials at high temperature is also required.

This International Standard can improve the accuracy of Seebeck coefficient and electrical conductivity of bulk-type thermoelectric materials and provide reliable and compatible data to interested parties. So it will facilitate industrial development through prompt dissemination of these measurement methods.