The phase purity of faceted LnScO3 (Ln = La, Nd, Sm, Gd) nanoparticles, synthesized from a mixed-cation hydroxide gel, is enhanced via water vapor control in a hydro-sauna synthesis method. Hydro-sauna is an open-system technique in which precursors are calcined in a humid environment. It can produce LnScO3 with low-index facets, well suited for catalytic supports and fundamental studies of catalyst-support interactions. To form LnScO3, this method requires some optimal, relatively low (&lt; 20 Torr) partial pressure of water. Precise control over this partial pressure is required to avoid generation of secondary phases such as Ln2O3, LnOOH, and Ln(OH)3—all three of which have been identified as potential intermediates for LnScO3 formation. In this work, density functional theory is used to calculate trends in formation energy of these phases across the lanthanide series. The increased stability of the hydroxide phases of certain lanthanides, e.g. La or Gd, informs the conditions required to generate pure perovskite phase LnScO3 material across the series. X-ray diffraction demonstrates the potential of using these DFT-calculated trends to modify hydro-sauna synthesis conditions, generating phase-pure LnScO3 for multiple lanthanides. This general approach of controlling water vapor pressure for optimal hydro-sauna synthesis may be applied to other material systems to generate shape-controlled, phase-pure nanoparticles for a variety of applications.

Water vapor controlled hydro-sauna synthesis of phase-pure LnScO3

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