Standardisation in thermoelectric transport properties measurements - the Cardiff NEDO laboratories and DLR Cologne program

The need for ensuring accurate and consistent experimental data is crucial for the success of any materials development programme. A current European funded research project "NanoThermEl" combines the talents of several leading research centres from across Europe in developing improved thermoelectric materials with reduced thermal conductivity, based on nano-sized particles. An essential requirement in this programme is the thermoelectric characterisation of new samples including measurements of Seebeck coefficient, electrical conductivity, thermal conductivity and the resulting dimensionless figure-of-merit ZT over a wide temperature range. A considerable number of samples have to be evaluated throughout the project, this work being divided between two leading European thermoelectric characterisation laboratories, NEDO Cardiff and DLR Germany. The use of different measurement techniques, sample geometrical requirements and equipment however meant that some form of measurement standardisation was necessary between partners, ensuring that meaningful and comparative data would result. This paper describes how this was achieved by defining suitable standardisation and round robin tests. Such tests are expected to encourage further such standardisation to be carried out between thermoelectric semiconductor research laboratories, thus increasing confidence and trace ability of published data. A proposal "SemiStand" has been recently submitted to the European Union with the aim of providing funding to achieve this goal.