Back to Search Start Over

Selective Synthesis of Defect-Rich LaMnO 3 by Low-Temperature Anion Cometathesis.

Authors :
Tran GT
Wustrow A
O'Nolan D
Tao S
Bartel CJ
He T
McDermott MJ
McBride BC
Chapman KW
Billinge SJL
Persson KA
Ceder G
Neilson JR
Source :
Inorganic chemistry [Inorg Chem] 2024 Feb 19; Vol. 63 (7), pp. 3250-3257. Date of Electronic Publication: 2023 Dec 27.
Publication Year :
2024

Abstract

The synthesis of complex oxides at low temperatures brings forward aspects of chemistry not typically considered. This study focuses on perovskite LaMnO <subscript>3</subscript> , which is of interest for its correlated electronic behavior tied to the oxidation state and thus the spin configuration of manganese. Traditional equilibrium synthesis of these materials typically requires synthesis reaction temperatures in excess of 1000 °C, followed by subsequent annealing steps at lower temperatures and different p (O <subscript>2</subscript> ) conditions to manipulate the oxygen content postsynthesis (e.g., LaMnO <subscript>3+ x </subscript> ). Double-ion exchange (metathesis) reactions have recently been shown to react at much lower temperatures (500-800 °C), highlighting a fundamental knowledge gap for how solids react at lower temperatures. Here, we revisit the metathesis reaction, LiMnO <subscript>2</subscript> + LaOX, where X is a halide or mixture of halides, using in situ synchrotron X-ray diffraction. These experiments reveal low reaction onset temperatures (ca. 450-480 °C). The lowest reaction temperatures are achieved by a mixture of lanthanum oxyhalide precursors: 2 LiMnO <subscript>2</subscript> + LaOCl + LaOBr. In all cases, the resulting products are the expected alkali halide salt and defective La <subscript>1-ϵ</subscript> Mn <subscript>1-ϵ</subscript> O <subscript>3</subscript> , where ϵ = x /(3 + x ). We observe a systematic variation in defect concentration, consistent with a rapid stoichiometric local equilibration of the precursors and the subsequent global thermodynamic equilibration with O <subscript>2</subscript> (g), as revealed by computational thermodynamics. Together, these results reveal how the inclusion of additional elements (e.g., Li and a halide) leads to the local equilibrium, particularly at low reaction temperatures for solid-state chemistry.

Details

Language :
English
ISSN :
1520-510X
Volume :
63
Issue :
7
Database :
MEDLINE
Journal :
Inorganic chemistry
Publication Type :
Academic Journal
Accession number :
38150180
Full Text :
https://doi.org/10.1021/acs.inorgchem.3c03305