Evaluating the performance of a thermoelectric material is time-consuming because it is necessary to create many samples with different electron concentrations and evaluate the performance of each sample. A research team led by Hiromich Ohta, an associate professor of Nagoya University, developed a new technology for the evaluation of a thermoelectric material that converts thermal energy to electric energy. The team members used strontium titanate for the thermoelectric material to measure thermoelectric energy conversion capacity and found that the structure of a field-effect transistor (EFT) is effective to the performance evaluation.
They built an EFT by evaporating a metallic electrode and a gate insulator on a strontium titanate material. They measured the thickness and electron concentration of the two-dimensional electron generated from strontium titanate simultaneously, and successfully measured thermoelectric energy conversion capacity by controlling the voltage on the gate terminal of the EFT. As a result of the measurement, they found that thermoelectric energy conversion capacity decreased initially, but it increased to about five times when the thickness of the gas becomes as thin as in nanometers. The new technology shortens the time for performance evaluation. At the same time, the research team expects the new technology to lead to early discovery of a high-performance thermoelectric material.