Defect-Accommodating Intermediates Yield Selective Low-Temperature Synthesis of YMnO 3 Polymorphs

Year: 2020

Type: article

Abstract: In the synthesis of complex oxides, solid-state metathesis provides low-temperature reactions where product selectivity can be achieved through simple changes in precursor composition. The influence of precursor structure, however, is less understood in solid-state synthesis. Here we present the ternary metathesis reaction (LiMnO 2 + YOCl → YMnO 3 + LiCl) to target two yttrium manganese oxide products, hexagonal and orthorhombic YMnO 3, when starting from three different LiMnO 2 precursors. Using temperature-dependent synchrotron X-ray and neutron diffraction, we identify the relevant intermediates and temperature regimes of reactions along the pathway to YMnO 3 . Manganese-containing intermediates undergo a charge disproportionation into a reduced Mn(II,III) tetragonal spinel and oxidized Mn(III,IV) cubic spinel, which lead to hexagonal and orthorhombic YMnO 3, respectively. Density functional theory calculations confirm that the presence of Mn(IV) caused by a small concentration of cation vacancies (∼2.2%) in YMnO 3 stabilizes the orthorhombic polymorph over the hexagonal. Reactions over the course of 2 weeks yield o-YMnO 3 as the majority product at temperatures below 600 °C, which supports an equilibration of cation defects over time. Controlling the composition and structure of these defect-accommodating intermediates provides new strategies for selective synthesis of complex oxides at low temperatures.

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.0c02023

Authors: Paul K. Todd, Allison Wustrow, Rebecca D. McAuliffe, Matthew J. McDermott, Gia Thinh Tran, Brennan C. McBride, Ethan D. Boeding, Daniel O’Nolan, Chia-Hao Liu, Shyam S. Dwaraknath, Karena W. Chapman, Simon J. L. Billinge, Kristin A. Persson, Ashfia Huq, Gabriel M. Veith, James R. Neilson

Institutions: Colorado State University, Oak Ridge National Laboratory, Lawrence Berkeley National Laboratory, University of California, Berkeley, Stony Brook University, Brookhaven National Laboratory, Columbia University

Language: English

Topic: Inorganic Chemistry and Materials

Subfield: Inorganic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: green

Funders: U.S. Department of Energy, Alfred P. Sloan Foundation, Battelle, National Energy Research Scientific Computing Center, Office of Science, Basic Energy Sciences, Argonne National Laboratory, Oak Ridge National Laboratory, Brookhaven National Laboratory

OpenAlex ID: W3081851237