Enhancement of the thermopower controlled by spin state in La0.9−xEuxCa0.1CoO3

• The thermopower for La0.9Ca0.1CoO3 is enhanced by Eu doping.
• The Co3+ ions undergo a spin-state transition induced by Eu doping.
• The thermopower enhancement originates from the spin-state transition.

The effect of the spin state on the thermopower has been studied in La0.9−xEuxCa0.1CoO3 (x=0.0, 0.05, 0.1 and 0.15) through the thermopower, X-ray photoelectron spectroscopy (XPS), and magnetic measurements. The thermopower is obviously enhanced by Eu doping. Both XPS and magnetic properties reveal that the spin state of Co3+ ions is the driving force for the thermopower in La0.9−xEuxCa0.1CoO3. Moreover, we adopt the theoretical model proposed by Koshibae et al. to explain well the enhancement of the thermopower which is induced by spin-state transition. This investigation provides an effective path for the research and development of new thermoelectric oxides.