Atomic Scale Verification of Oxide-Ion Vacancy Distribution near a Single Grain Boundary in YSZ

Jihwan An,Hark B Lee,Fritz B Prinz,Ai Leen Koh,Hee Joon Jung,Robert Sinclair,Joop Schoonman,Joong Sun Park,Turgut M Gür

doi:10.1038/srep02680

Abstract

This study presents atomic scale characterization of grain boundary defect structure in a functional oxide with implications for a wide range of electrochemical and electronic behavior. Indeed, grain boundary engineering can alter transport and kinetic properties by several orders of magnitude. Here we report experimental observation and determination of oxide-ion vacancy concentration near the Σ13 (510)/[001] symmetric tilt grain-boundary of YSZ bicrystal using aberration-corrected TEM operated under negative spherical aberration coefficient imaging condition. We show significant oxygen deficiency due to segregation of oxide-ion vacancies near the grain-boundary core with half-width < 0.6 nm. Electron energy loss spectroscopy measurements with scanning TEM indicated increased oxide-ion vacancy concentration at the grain boundary core. Oxide-ion density distribution near a grain boundary simulated by molecular dynamics corroborated well with experimental results. Such column-by-column quantification of defect concentration in functional materials can provide new insights that may lead to engineered grain boundaries designed for specific functionalities.

Highlights

This study presents atomic scale characterization of grain boundary defect structure in a functional oxide with implications for a wide range of electrochemical and electronic behavior
Electron energy loss spectroscopy measurements with scanning transmission electron microscopy (TEM) indicated increased oxide-ion vacancy concentration at the grain boundary core
We present atomic-scale quantification of oxide-ion vacancy concentration near the S13 (510)/ [001] symmetric tilt grain-boundary of a yttria-stabilized zirconia (YSZ) bicrystal using aberration-corrected TEM operated under negative spherical aberration coefficient imaging condition

Summary

Introduction

This study presents atomic scale characterization of grain boundary defect structure in a functional oxide with implications for a wide range of electrochemical and electronic behavior. F luorite-structured oxides such as yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) are commonly employed in solid oxide fuel cells (SOFCs), oxygen sensors, electrolyzers, catalytic converters for emission control, etc For these applications, ion transport and gas-solid surface exchange are highly influenced by the local atomic structure or defect distribution at grain boundaries (GBs). None of these techniques have yet been applied to within a nanometer range of GBs to directly observe and quantify the gradual change in the occupancy of oxygen columns (i.e., oxide-ion vacancy concentration), which is crucial for understanding electrical and transport properties at GBs. In this report, we present atomic-scale quantification of oxide-ion vacancy concentration near the S13 (510)/ [001] symmetric tilt grain-boundary of a YSZ bicrystal using aberration-corrected TEM operated under negative spherical aberration coefficient imaging condition. Such column-by-column quantification of defect concentration in functional materials can provide new insights that may lead to engineered grain boundaries with specific functionalities

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