Abstract
We present a study of the thermal conductivity and the thermopower of single crystals of with . For all Sr concentrations, has rather low values. For the insulators this arises from a suppression of the phonon thermal conductivity by lattice disorder due to temperature- and/or doping-induced spin-state transitions of the Co ions. For larger , the heat transport by phonons remains low, but an additional contribution from mobile charge carriers causes a moderate increase of . The thermopower of the low-doped crystals is positive and shows a pronounced maximum as a function of temperature. With increasing , this maximum broadens strongly and its magnitude decreases. For the highest Sr content , becomes negative in the intermediate temperature range. From , , and the electrical resistivity , we derive the thermoelectric figure of merit . For intermediate Sr concentrations we find notably large values of , indicating that Co-based materials could be promising candidates for thermoelectric cooling.
- Received 11 January 2005
DOI:https://doi.org/10.1103/PhysRevB.72.155116
©2005 American Physical Society