Influence of the preparation method on the microstructure and physicochemical properties of the (Ca,Bi)[3]Co[4]O[9+?] cobaltites

Abstract

The ceramic samples of the (Ca,Bi)3Co4O9+? were prepared using solid-state reactions and citrate methods. The influence of the preparation method on the crystal and microstructural, physicochemical and functional characteristics of these materials was studied. The temperature-time processing regimes of the (Ca,Вi)3Co4O9+? ceramics were selected. It is found that Ca2.8Bi0.2Co4O9+? solid solution, which was prepared by a citrate method, demonstrated the maximal value of the power factor (240 ?W/(m · K2) at 1,100 K) among the ceramics prepared. It is shown that citrate method has significant advantages in comparison with the solid-state reactions one because it allows to reduce energy consumption during the synthesis and at the same time to prepare more dense, fine-grained, and electrically conducting ceramics with a lower linear thermal expansion coefficient and higher power factor.