Thermoelectric Bi2Sr2Co1.8Ox textured ceramics: effect of Ag addition

Resumen del trabajo presentado al LII Congreso Anual de la Sociedad Española de Cerámica y Vidrio celebrado en Burgos del 3 al 6 de octubre de 2012.
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 (1 wt.%). The composites electrical resistivity is lower than that of pure Bi2Sr2Co1.8Ox 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 1 wt.% Ag.