Decomposition of Ag2C2O4 in a spark plasma sintering apparatus: morphological study and application for materials joining

Abstract Silver oxalate Ag2C2O4 is an interesting compound from both fundamental and practical viewpoints. Decomposition of Ag2C2O4 results in the formation of metallic silver, whose size and morphology can be tailored for different applications. In this work, we focused on the morphological features of silver that forms upon decomposition of Ag2C2O4 in a spark plasma sintering (SPS) apparatus. While crystals heated in a conventional furnace decompose to produce silver in the form of a pseudomorph, decomposition induced by heating in a SPS chamber at a rate of 30 °C·min-1 via a pressureless process results in the formation of foam-like porous silver. Decomposition of Ag2C2O4 was also carried out under pressure by placing the powder between copper plates and heating the assembly in a SPS die. A feasibility study has shown that Ag2C2O4 powders can be used for joining copper plates in a fast process enabled by the SPS method. Joints formed by the SPS method at 300°C and 13 MPa were formed by silver with 500-nm crystallites; the shear strength of the joints was 45 MPa.