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There has been extensive work on the equilibrium shape of isolated nanoparticles with internal boundaries and also single crystals on substrates. Surprisingly, almost shockingly, there has been ver...

Gadolinium scandate (GdScO3) has been synthesized at 300 °C through the decomposition of a mixed cation hydroxide hydrogel in a humid environment. Increasing the reaction temperature produced larger particles that better adopted the Wulff shape. A lack of water vapor during the synthesis caused the solid network of the hydrogel to collapse upon heating so an amorphous xerogel was produced. Water vapor in the system imbibed the hydrogel and allowed for greater diffusion of the atomic species to allow for crystallization into the perovskite phase at temperatures lower than typical sol–gel processes. Temperatures less than 300 °C, or an excess of water vapor, promoted the formation of Gd(OH)3 and ScOOH in addition to or in lieu of GdScO3.

A general approach to the formation of well-faceted nanoparticles is discussed and successfully applied to the production of several rare-earth scandates. Two steps were used, with higher temperatures first to nucleate the perovskite phase, followed by lower temperatures to smooth the particle surfaces. Exploiting these two different regimes led to smaller nanoparticles with more faceting. This general approach may be tailored to other material systems as a step towards producing shape-controlled nanoparticles for a desired application.