Abstract
The oxygen stoichiometry and the electronic transport properties of [Ca2CoO3−δ]q[CoO2] (q = 0.62) have been investigated in the temperature range 300 to 875 °C as a function of oxygen partial pressure by means of thermogravimetry, conductivity, and Seebeck coefficient measurements. A defect chemical model has been established to assess the concentrations of the different relevant defects in [Ca2CoO3−δ]q[CoO2], including the concentration of mobile holes. By controlling the oxygen content, the hole concentration changes from 0.32 to 0.42 per formula unit, leading to a significant variation of both the conductivity and the Seebeck coefficient. The transport properties of [Ca2CoO3−δ]q[CoO2] at high temperatures are discussed, and it is concluded that the electronic conduction is by itinerant holes—rather than by localized small polarons. Furthermore, it is shown that the concentration-dependent Seebeck coefficient cannot be described by Heikes’ formula in the tested temperature range despite its widespread u...
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
