ICT2014 Abstracts

Comparative measurements of the Seebeck coefficient are challenging due to the diversity of instrumentation and measurement protocols. The implementation of standardized measurement protocols and the use of Standard Reference Materials (SRMs^®), for example, the recently certified NIST SRM^® 3451 “Low Temperature Seebeck Coefficient Standard (10 K - 390 K)”, will allow reliable interlaboratory data comparison and accelerate the development of more efficient thermoelectric materials and devices. Due to different practical requirements in both instrumentation and sample contact methodology, a complementary SRM^® is in development for the high temperature regime. In addition to the evaluation of candidate materials, it was necessary to conduct substantial experimental evaluation of the measurement practices employed in both commercially available and custom developed instrumentation. We therefore present a comparative overview of these commonly adopted Seebeck coefficient measurement practices. First, we examine the influence of asynchronous temporal and spatial measurement of electric potential and temperature. Second, we examine the influence of poor thermal contact between the measurement probes and the sample. This is especially critical at high temperature, wherein the prevalent mode of measuring surface temperature is facilitated by pressure contact. Each topic will include the comparison of data measured using different measurement techniques and using different probe arrangements. Using these analyses, we will provide recommended measurement protocols to guide members of the thermoelectric materials community in performing more accurate measurements and in evaluating more comprehensive uncertainty limits.