Thermoelectric properties of Al and Mn double substituted ZnO

The effects of Al and Mn single and double substitution on structure, composition, and thermoelectric properties of ZnO have been investigated in three series of compounds; Zni(1-x)Al(x)O, Zn1-xMnxO (x=0,0.02,0.04,0.06,0.08) and Zn1-2xAlxMnxO (x=0,0.01,0.02,0.03,0.04) prepared by thermal decomposition method. While the lattice structure is not affected by the substitutions, properties of the material are. Al and Mn have opposite effects on electrical conductivity and Seebeck coefficient of ZnO. Al substitution leads to an increase in electrical conductivity while Mn substitution increases absolute value of Seebeck coefficient. Double substituted samples seem to exhibit the effects from both ions though the increase in absolute value of Seebeck coefficient is less significant comparing to that observed in Mn single substituted samples. Nevertheless, the change in electrical conductivity is more pronounced and dominant in the power factor calculation. Thus the most conductive sample in this work, Zn0.98Al0.02O, shows the highest power factor of 1.03x10(-4) WK-2 m(-1) at 800 K. The best double substituted sample is Zn0.98Mn0.01Al0.01O which gives a power factor of 4.79x10(-5) WK-2 m(-1) at the same temperature.