Screen-printed Cu3BiS3-polyacrylic acid composite coatings

A technique for preparing electrically conductive coatings of Cu3BiS3 powder in polyacrylic acid matrix is presented. Bi2S3 powder obtained by chemical precipitation was introduced into a freshly prepared CuS chemical deposition bath. After the initial nucleation period, CuS started to deposit on the Bi2S3 surface. The as-obtained CuS-Bi2S3 powder was mixed with polyacrylic acid aqueous solution, and the resulting mixture was used as a paste to form a screen-printed composite coating. Up to 200 degrees C the film behaves like a simple CuS film; the sheet resistance is around 100 Ohm and the crystallized phase in the composite is CuS (Covellite). When the temperature is equal or higher than 250 degrees C, atomic diffusion at the CuS-Bi2S3 interface is promoted, leading to the formation of the ternary compound Cu3BiS3 (Wittichenite) in the composite film. The formation of the compound depends on the temperature, relative abundance of the Bi2S3 and CuS components in the CuS-Bi2S3 pigment, as well as on the annealing atmosphere.