Reactive intermediate phase cold sintering in strontium titanate

Abstract

Dense (>96% theoretical) strontium titanate ceramics were fabricated at 950 °C (conventional sintering temperature > 1400 °C) using a reactive intermediate phase cold sintering process. An aqueous solution of SrCl₂ mixed with TiO₂ nanoparticles was added to SrTiO₃ powders and pressed at 180 °C to obtain a highly compacted green body. During the post-press heating step at 950 °C, the TiO₂ and SrCl₂ create in-filling micro-reactions around each grain resulting in dense (>96%) SrTiO₃ ceramics. Nano- and micron-sized starting powders were used, demonstrating that this reactive intermediate phase cold sintering route can densify a wide range of starting powder sizes, as it not reliant on an amorphous-to-crystalline precipitation through the terrace ledge kink mechanism, as has been identified repeatedly in previous cold sintering mechanisms. Moreover, this process has the potential to densify a wide variety of functional oxides, as a range of different low-temperature chemical synthesis routes could be used.