Enhancement of the power factor of [Bi_(1.68)Ca_2O_4]~(RS)[CoO_2]_(1.69)- Ag composites prepared by the spray-drying method

摘要

[Bi_(1.68)Ca_2O_4]~(RS)[CoO_2]_(1.69) (BCCO) sample and Ag-BCCO composites (with 10, 20 or 30 wt% Ag) have been prepared by the spray-drying technique and uniaxially/isostatically packed. Scanning electron microscopy reveals that the Ag particles are well distributed in the BCCO cobaltite matrix at low Ag contents. The Ag particles have an important effect on densification and grain orientation of the samples, with a direct impact on their electrical conductivity. The electrical conductivity is higher for the uniaxial samples and increases with the Ag content up to 20% in weight, while the Seebeck coefficient is hardly affected. These features induce an improvement of the power factor, reaching a maximum value of 2.2 μW K~(-2) cm~(-1) at ～1050 K for the uniaxial sample with 20 wt% Ag. Our results suggest that the spraydrying technique is a promising method to obtain composites with a well-dispersed secondary phase.