ICT2014 Abstracts

The mechanical integrity of thermoelectric materials is very important, especially for waste heat harvesting applications when the materials are subjected to stresses generated by thermal transients generally by cold start-up and hot shut down of thermoelectric generators.  However, the crack length in brittle materials can be modified by mechanisms other than applied external stresses.  For example, cutting, grinding and polishing operations during module fabrication can expose thermoelectric materials to water vapor and cutting fluids, which can in turn lead to environmentally assisted slow crack growth.  Observations of slow crack growth of growth in a number of thermoelectric materials will be discussed for a range of environmental conditions including water vapor as well as oil and water-based machining fluids.  Also, cracks that are present in solids can diffusively heal at homologous temperatures greater than 0.6.  Such crack healing processes could have much different effects depending on details of a particular application, for example automotive applications versus stationary furnaces for which the maximum temperature may be maintained for long periods of time.  Thus, both mechanisms (environmentally assisted crack growth and crack healing) can modify crack length and thus affect the mechanical properties of thermoelectrics.