Deep crystallization induced high thermal conductivity of low-temperature sintered Ag nanoparticles

•Silver nanoparticles (Ag NPs) paste is chemically fabricated.•The organic shells outside the Ag NPs flocculated by nitrate are thinner.•Thermal conductivity of Ag NPs sintered at 453 K is above 100 W/K-m.•Large amounts of twin boundaries are observed in the sintered Ag NPs.•Deep crystallization by Ostwald ripening is probably the sintering mechanism.

We studied the mechanism and morphological evolution of a thermal interface material prepared by pressureless sintering of a paste containing silver nanoparticles (Ag NPs) flocculated with citrate or nitrate. A high thermal conductivity (>100 W/K-m) was obtained from the material sintered at 453 K for 30 min. Significant crystallization and large amounts of twins were observed in the material. These results could be ascribed to the thinner organic shells surrounded the Ag NPs, resulting in easy activation of Ostwald ripening.