Effect of Ag addition on the mechanical and thermoelectric performances of annealed Bi2Sr2Co1.8x textured ceramics

Abstract

Bi2Sr2Co1.8Ox/Ag composites with small amounts of Ag have been synthesized by a sol-gel via nitrates reaction and directionally grown from the melt. Some of the obtained samples were annealed in order to obtain the thermoelectric phase as the major one. As-grown and annealed samples were microstructurally characterized to determine the phases distribution and alignment. Moreover, thermoelectric and mechanical characteristics of annealed samples were determined by the four-probe technique and by three point flexural strength tests, respectively. Scanning electron microscopy revealed that Ag particles appear dispersed among well oriented ceramic grains with large size, providing a plastic flow region which increases the flexural strength for the optimally Ag added samples (1wt.%). The composites electrical resistivity is lower than that of pure Bi 2Sr 2Co 1.8O x while Ag addition does not significantly affect thermopower values. The resistivity reduction leads to power factor improvements of ∼50%, compared with pure samples, for Ag additions of 1wt.% Ag. © 2012 Elsevier Ltd.