The effects of citric acid on the synthesis and performance of silver–tin oxide electrical contact materials

Abstract

A sol–gel auto-combustion method was developed to synthesize the Ag–SnO2 composite powders, which were then used as the starting material to prepare Ag–SnO2 electrical contact materials by hot pressing. It was found that citric acid strongly influences the thermal behaviors, phase evolution, morphology and composition distribution of the Ag–SnO2 composite powders. During the synthesis of Ag–SnO2 composite powders, citric acid can facilitate the formation of sol solution, lower the energy required for the decomposition of dry gel, and reduce the agglomeration of particles. Besides, a comparatively high molar ratio of citric acid to metal ions prevents effectively the occurrence of composition segregation in the Ag–SnO2 electrical contact materials. Therefore, the prepared Ag–SnO2 electrical contact materials have good performances in density, hardness and electric conductivity.