High-temperature electron microscopy study of ThO2 microspheres sintering

Polycrystalline and single-crystal two-grain systems were further investigated to monitor the formation of a neck during heat treatment. For single crystals, the topological evolution was found to agree well with the models, whereas the establishment of neck between two polycrystalline microspheres deviated from the expected trend, with the formation of intermediate large-size crystallites. Such modification was mainly assigned to the microstructures of the particles used, showing that the level of polycrystallinity of the powder and its initial porosity, which both arose from the synthesis method, must be considered carefully to evaluate its sintering capability.