Open AccessInsights into Oxygen Migration in LaBaCo2O6−δ Perovskites from In Situ Neutron Powder Diffraction and Bond Valence Site Energy Calculations
Author(s) -
Fabian Hesse,
Iván da Silva,
JanWillem G. Bos
Publication year - 2022
Publication title -
chemistry of materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.741
H-Index - 375
eISSN - 1520-5002
pISSN - 0897-4756
DOI - 10.1021/acs.chemmater.1c03726
Subject(s) - vacancy defect , neutron diffraction , materials science , valence (chemistry) , ionic bonding , orthorhombic crystal system , crystallography , perovskite (structure) , oxide , chemical physics , crystal structure , condensed matter physics , ion , chemistry , metallurgy , physics , organic chemistry
Layered cobalt oxide perovskites are important mixed ionic and electronic conductors. Here, we investigate LaBaCo 2 O 6-δ using in situ neutron powder diffraction. This composition is unique because it can be prepared in cubic, layered, and vacancy-ordered forms. Thermogravimetric analysis and diffraction reveal that layered and disordered samples have near-identical oxygen cycling capacities. Migration barriers for oxide ion conduction calculated using the bond valence site energy approach vary from E b ∼ 2.8 eV for the cubic perovskite to E b ∼ 1.5 eV for 2D transport in the layered system. Vacancy-ordered superstructures were observed at low temperatures, 350-400 °C for δ = 0.25 and δ = 0.5. The vacancy ordering at δ = 0.5 is different from the widely reported structure and involves oxygen sites in both CoO 2 and LaO planes. Vacancy ordering leads to the emergence of additional migration pathways with low-energy barriers, for example, 1D channels with E b = 0.5 eV and 3D channels with E b = 2.2 eV. The emergence of these channels is caused by the strong orthorhombic distortion of the crystal structure. These results demonstrate that there is potential scope to manipulate ionic transport in vacancy-ordered LnBaCo 2 O 6-δ perovskites with reduced symmetry.