Mechanistic studies of high temperature friction reduction in silver tantalate

Silver tantalate (AgTaO3) has recently been identified as an excellent solid lubricant in sliding contacts at high temperatures. In this Letter, molecular dynamics simulations and experimental measurements are used to investigate the underlying mechanisms. Predicted and measured friction is observed to decrease with increasing temperature. Transmission electron microscopy reveals clusters of Ag surrounded by Ta2O5 in the surface layer. These features are reproduced and characterized quantitatively in the simulations. The findings indicate that low friction at high temperatures is enabled by the joint contributions of the hard Ta2O5 phase and lubricious Ag clusters in the shear- and temperature-induced surface layer.