Pressure Induced Stability Enhancement of Cubic Nanostructured CeO2 †.

Mariano Andrés Paulin,Mohamed Mezouar,Joaquin Sacanell,Ana Gabriela Leyva,Gaston Garbarino

doi:10.3390/nano10040650

Mariano Andrés Paulin, Mohamed Mezouar + Show 3 more

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https://doi.org/10.3390/nano10040650

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Abstract

Ceria (CeO2)-based materials are widely used in applications such as catalysis, fuel cells and oxygen sensors. Its cubic fluorite structure with a cell parameter similar to that of silicon makes it a candidate for implementation in electronic devices. This structure is stable in a wide temperature and pressure range, with a reported structural phase transition to an orthorhombic phase. In this work, we study the structure of CeO2 under hydrostatic pressures up to 110 GPa simultaneously for the nanometer- and micrometer-sized powders as well as for a single crystal, using He as the pressure-transmitting medium. The first-order transition is clearly present for the micrometer-sized and single-crystal samples, while, for the nanometer grain size powder, it is suppressed up to at least 110 GPa. We show that the stacking fault density increases by two orders of magnitude in the studied pressure range and could act as an internal constraint, avoiding the nucleation of the high-pressure phase.

Highlights

Cerium dioxide, or ceria, is widely known and studied because of its uses in catalysis, as a solid oxide fuel cell material and, much more recently, as a potential component of spintronic devices due to its large dielectric constant and the appearance of magnetism in several conditions [1,2,3]
26 GPa, new weak reflections are observed for the micrometer grain size powder (MICRO) sample that can be indexed with the reported orthorhombic phase
A first-order phase transition occurring at 26(1) and 30(3) GPa is present for the MICRO and CRYSTAL samples, respectively, while for the NANO sample, it is inhibited up to a pressure at least four times larger

Summary

Introduction

Ceria, is widely known and studied because of its uses in catalysis, as a solid oxide fuel cell material and, much more recently, as a potential component of spintronic devices due to its large dielectric constant and the appearance of magnetism in several conditions [1,2,3]. This unusual behavior, which includes a negative compressibility, was observed using silicone oil, methanol/ethanol, or without a PTM This result was explained in terms of the difficulty in observing the high-pressure phase due to the peak broadening related to the nanometric grain size of the powder. There was a report showing a reduction in the structural phase transition to 20 GPa observed on the nanoparticles of 9–15 nm [10]. To the best of our knowledge, those are the studies performed on ceria nanoparticles for pressures above 30 GPa. In all of the mentioned cases involving nanoparticles, the use of silicon oil or a 4:1 methanol/ethanol mixture as the PTM, or their absences, does not assure the best possible hydrostatic experimental conditions

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