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Oxide interfaces in disarray

Microscope image, bright blue background with bright green oxides

Atomic-scale imaging informs interface models for oxygen defect formation during disordering of oxides used in energy and computing.


Exploration of disorder at material interfaces could lead to better device performance

March 3, 2020
March 3, 2020

The structure of an interface at which two materials meet helps determine the performance of the computers and other devices we use every day. However, understanding and controlling interface disorder at the atomic level is a difficult materials science challenge.

A research team at PNNL and Texas A&M University combined cutting edge imaging and numerical simulations to examine disordering processes in widely used oxide materials. They found that certain oxide interface configurations remain stable in extreme environments, suggesting ways to build better performing, more reliable devices for fuel cells, space-based electronics, and nuclear energy.

Visualizing the disordering process

As reported in Advanced Materials Interfaces (Asymmetric Lattice Disorder Induced at Oxide Interfaces,” DOI: 10.1002/admi.201901944) the team set out to examine interfaces between pyrochlore-like and perovskite oxides, two common classes of functional materials used in energy and computing technologies. While most past work has focused on individual bulk materials, less attention has been paid to interfaces connecting them, as would be the case in a device. In particular, it is not clear how interface features, such as composition, bonding, and possible defects, govern disordering processes.

Funded by PNNL’s Nuclear Process Science Initiative (NPSI), the team employed experimental and theoretical methods to study the interface at different stages of disorder introduced through ion irradiation. They imaged the local structure of the material using high-resolution scanning transmission electron microscopy and convergent beam electron diffraction, which showed that the bulk of the two materials disordered (amorphized) before the interface. After further irradiating the material, they found that a band region near the interface had remained crystalline, while the rest of the structure had become amorphous.

To understand this behavior, the team turned to a technique called electron energy loss spectroscopy, which allowed them to examine the atomic-scale chemistry and defects formed at the interface. Their measurements revealed the presence of substantial amounts of defects called oxygen vacancies, which can greatly affect properties such as magnetism and conductivity. Based on these observations, the team constructed a theoretical model of the interface and explored the effect of different interface configurations on the tendency to form vacancies.

“In our model we are able to systematically vary interface features, such as crystal structure, intermixing, and strain, to see their effect on defect formation. We found that the structure of the materials on both sides of the interface can influence where defects are likely to form first,” explained Steven R. Spurgeon, a PNNL materials scientist. “Our model suggests that by selecting appropriate crystal structures and controlling how they connect, it may be possible to dictate the sequence of defect formation, which would allow us to enhance the properties of these materials.”

The team is exploring other interface structures and chemistries, with an eye toward improving the performance of oxides used in extreme environments.

The study was conducted as part of the NPSI project, “Damage Mechanisms and Defect Formation in Irradiated Model Systems,” led by Spurgeon.

Research Team

Steven Spurgeon (PNNL), Tiffany Kaspar (PNNL), Vaithiyalingam Shutthanandan (Environmental Molecular Sciences Laboratory at PNNL), Jonathan Gigax (Texas A&M), Lin Shao (Texas A&M), Michel Sassi (PNNL).
February 20, 2020
JULY 25, 2019
News Release

Containing Hydrogen in a Materials World

Researchers at the Department of Energy’s Pacific Northwest National Laboratory and Sandia National Laboratories have joined forces to reduce costs and improve the reliability of hydrogen fueling stations.
JANUARY 24, 2017
News Release

The Contradictory Catalyst

Using a natural catalyst from bacteria for inspiration, researchers have now reported the fastest synthetic catalysts to date for hydrogen production-- producing 45 million hydrogen molecules per second.

Center for Molecular Electrocatalysis


An Energy Frontier Research Center

United States

The 21st century brings with it the grand challenge of changing the way we generate, supply, transmit, store, and use energy to meet the world’s growing demands. To address this challenge, the U.S. Department of Energy has established a network of Energy Frontier Research Centers throughout the nation, each focusing on specific scientific questions and problems. PNNL is the lead institution for the Center for Molecular Electrocatalysis (CME), an EFRC established in 2009 to determine the fundamental principles needed for efficient interconversion of electrical energy and chemical bonds through precise control of electron and proton transfers.

At this center for collaboration and innovation, researchers work with new and specialized tools to understand and manipulate matter on the atomic and molecular scales. Teams are made up of researchers from universities, national laboratories, and private industry. Researchers work together to design electrocatalysts that store electrical energy in chemical bonds and allow their conversion back to electricity on demand. This research can improve reactions important for solar energy storage and fuel cells. Specifically, CME researchers are working to make hydrogen reactions faster and more efficient, discover more selective catalysts to split molecular oxygen, and improve important aspects of molecular nitrogen catalysts.

For detailed information or research highlights, click here.

Institute for Integrated Catalysis


Currently, 80 percent of all chemical products and energy carriers are made using catalysts in at least one of the processing steps, producing an economic impact estimated to be over $10 trillion per year worldwide. The long-term transition to a sustainable economy requires not only reinventing the large processes of today, but also enabling the harvest and use of dispersed renewable carbon and energy resources. These challenges define the mission of the Institute for Integrated Catalysis (IIC). We are providing the insight, the synthetic tools, and the engineering concepts to enable catalyzed chemical and chemical-electrical energy interconversions to minimize the carbon footprint of the global energy system. In addition, we are developing new experimental and theoretical tools to better understand the structure and properties of working catalysts to be used as guidelines for novel catalysts and reaction routes. And we are translating the fundamental insights gained into new catalytic technology.

Relieving the Pressure

We are developing new technologies that can operate at lower temperatures and pressures. To achieve this, we are learning from how enzymes, nature’s catalysts, handle the problem. By developing a foundational understanding of catalytic chemistries, we are designing new catalysts and catalytic synthesis routes. The IIC integrates more than 120 scientists and engineers from across the laboratory working in cross-disciplinary collaborations to address these challenges.