In
addition to uranium, thorium is a vital nuclear element
that
has broad potential for future nuclear energy applications. Herein,
we report the synthesis of cubic structured ThO2 nanocrystals
(NCs) based on the decomposition of their nitrate salt in air and
in a molten salt medium. Both the processes yield pure ThO2 NCs with average sizes of <100 nm. The ThO2 NCs synthesized
in the molten salt medium exhibit better crystallinity and a larger
average size of ∼75.1 nm with a narrow size distribution owing
to the high-temperature liquid growth environment. The ceramic sintered
from the salt-derived ThO2 NCs exhibits a considerably
higher relative density of 94.6% and similar thermal properties compared
with the ceramic fabricated from fine nanopowders (<10 nm) obtained
from direct thermolysis of metal nitrate. This study shows that thermal
decomposition in a molten salt medium could be an efficient method
for producing highly crystalline metal-oxide NCs of thorium-based
fuels used in nuclear energy applications.