Densification of oxides via cold sintering of hydrate precursors

A generalized cold sintering densification strategy based on a hydroxide precursor transformation route is proposed for oxides. The densification of MgO, CuO, ZnO and WO3 was achieved via cold sintering by using their corresponding hydroxides at temperatures not exceeding 450 degrees C. Nano-oxides formed by the decomposition of the hydroxides exhibited good low-temperature sinterability. The densification mechanisms mainly involved particle rearrangement promoted by in situ released water and intergranular diffusion accelerated by surface defects of the oxide particles generated from hydroxide decomposition. During the cold sintering process, the oxides with relatively higher solubility in a water vapor environment are more likely to form surface defects, which promoted water-aided densification. Owing to the possibility of obtaining the corresponding hydroxides for almost all oxides, this strategy renders cold sintering feasible for a wide range of materials.