Mineralizer effect on facet-controllable hydrothermal crystallization of perovskite structure YbFeO3 crystals

Abstract

Mineralizer is a key factor in the hydrothermal crystallization of most metal oxide materials. However, the effect of mineralizer on crystal facet growth is not well understood. Herein, YbFeO₃ is taken as a model compound to determine the effect of mineralizer on its shape evolution during a mild hydrothermal crystallization process. By adjusting the concentration and ratio of NaOH and KOH, the shapes of YbFeO₃ crystals showed two different facet formation routes: NaOH stabilizes {110} and {002} facets, while KOH stabilizes {101} facets. The percentage of each family of crystal facets could be tailored by changing the concentrations of mineralizer and NH₄⁺. The shape formation mechanism of YbFeO₃ was analyzed based on Bravais–Friedel–Donnay–Harker theory, in addition to their facet structures and interactions between crystal facets and Na⁺, K⁺ and NH₄⁺. This study will not only improve understanding of the role of mineralizers in oxide crystallization, but also provide a crystal facet controllable method for the hydrothermal synthesis of oxide materials with potential anisotropy applications.