Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers strain to improve electrical material and it's worth it

12.02.2013
Like turning coal to diamond, adding pressure to an electrical material enhances its properties. Now, University of Illinois at Urbana-Champaign researchers have devised a method of making ferroelectric thin films with twice the strain, resulting in exceptional performance.

Led by Lane Martin, a professor of materials science and engineering, the group published its results in the journal Advanced Materials.

Ferroelectric materials, metal oxides with special polarization properties, are used in a number of advanced electronics applications. When electricity is applied, they can switch their polarization, or the direction of their internal electric field, which makes them useful in devices such as computer memories and actuators. Ferroelectric materials are especially useful in aerospace applications because they are less susceptible to radiation than traditional semiconductors.

Strain in these materials can alter their properties and improve their performance. A lot of research in ferroelectric materials has focused on making strained thin films with alternating layers only a few nanometers thick of materials with slightly different crystal structures.

“It turns out that if you put pressure on certain types of materials, the properties completely change,” Martin said. “In our case we administer pressure by straining or stretching thin versions of these materials like one would stretch plastic wrap to fit on a bowl. You can induce things that don’t exist at ambient conditions; you can make phases and properties that don’t exist.”

The films are made of lead zirconate titanate (commonly called PZT).

The relative amounts of zirconium (Zr) and titanium (Ti) in the films determine the shape of the crystals. Traditionally, films of PZT have been made up of a single composition, grown on a substrate with a slightly different crystal structure to cause strain in the PZT. However, too much strain causes the PZT to revert to its original crystal structure. This limits researchers’ ability to change the properties of these materials for better device performance.

The Illinois researchers overcame this limitation by gradually shifting the concentrations of Zr and Ti as they grew the thin films, incrementally changing the crystal structure. From layer to layer, the structures are very similar, yet the composition of the PZT at the top and bottom of the film is very different, transitioning from a PZT composition with 80 percent Zr to 80 percent Ti. This gradual change, instead of the usual layered approach, results in little localized strain but large overall strain.

“We have taken a material with similar mechanical properties to a dinner plate, the same kind of hardness, and effectively figured out a way to stretch that plate without breaking it,” Martin said. “With our method, we’ve been able to extend our ability to strain these materials. We go to the nanoscale so we can pull on these films and dramatically change the shape, and that affects the properties.”

Thanks to the large strain, the compositionally graded PZT films not only have improved properties, but also entirely new properties. Most notably, the films have a built-in electric field, called an intrinsic potential. This means that it can perform some functions without needing an external current or field applied to it. In addition, it means that the material has a preferred polarity, which opens the door for new applications.

“This sort of built-in field is very useful,” said Karthik Jambunathan, a graduate student and co-author of the paper. “Otherwise you have to engineer similar effects using features not native to the materials to have the same thing happen, but it is much more difficult and less easily controlled. Here, it’s grown into the material to begin with.”

For example, ferroelectric materials widely have been used in memory applications that rely on spontaneous polarization. However, to read a bit of data in computer memories made with a traditional ferroelectric material, its polarity is switched. This means that every time the bit is read, it has to be re-written and compared to a reference bit. But if the material had a built-in electric potential, engineers could make bits that would not need to have their polarity switched to be read, so computer components made with the new material could be smaller, faster and longer lasting.

Now the Illinois team plans to further explore potential applications, as well as apply their gradient film technique to other types of ferroelectric materials in search of even more novel and unexpected properties.

“This is just the beginning,” Martin said. “There are an infinite number of varieties of gradients that you could think about. This is a smooth gradient, but we could skew it, or change what the end members are. Each one of these is going to give its own set of structures and potential properties that we haven’t even begun to scratch the surface of. I think the capacity for finding new types of materials and properties is really open here.”

The Defense Advanced Research Projects Agency, the Office of Naval Research, the Army Research Office and the Air Force Office of Scientific Research supported this work. Martin also is affiliated with the Frederick Seitz Materials Research Laboratory at the U. of I.

Editor’s notes: To reach Lane Martin, call 217-244-9162;
email lwmartin@illinois.edu.

The paper, “Unexpected Crystal and Domain Structures and Properties in Compositionally Graded PbZr1-xTixO3 Thin Films,” is available online

Lane Martin | University of Illinois
Further information:
http://www.illinois.edu

More articles from Materials Sciences:

nachricht Graphene assembled film shows higher thermal conductivity than graphite film
22.06.2018 | Chalmers University of Technology

nachricht Game-changing finding pushes 3D-printing to the molecular limit
20.06.2018 | University of Nottingham

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

New cellular pathway helps explain how inflammation leads to artery disease

22.06.2018 | Life Sciences

When fluid flows almost as fast as light -- with quantum rotation

22.06.2018 | Physics and Astronomy

Exposure to fracking chemicals and wastewater spurs fat cell development

22.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>