New Materials Hold Promise for Turbine, Antenna Use
Leonard Brillson, a professor in electrical and computer engineering, often hears from fellow Ohio State faculty in aerospace engineering how sensing devices can’t operate near aircraft turbine engines because of the intense heat.
His team develops materials called double perovskites: crystals of ceramics oxides with a cornucopia of magnetic and electronic properties — and the ability to withstand the high temperatures of those turbines.Brillson might just have a solution for them through his research with experts in chemistry and physics and working with Ohio State’s Center for Emergent Materials, one of the nation’s select National Science Foundation Materials Research Science and Engineering Centers.
The structure of perovskites consists of eight-sided building blocks, or octahedra — atoms that form four-sided pyramids arranged bottom to bottom. Four of these blocks group together like a cube with a different atom nestled in the center. The cubes stack together to form the perovskite crystal. In the double perovskite crystal, the center atom alternates between two different atoms, for example, iron (Fe) and molybdenum (Mo) in Sr2FeMoO6, to manipulate the magnetic qualities.
This exotic latticework of atoms gives double perovskites their unique electromagnetic properties, explains Brillson, who also holds a faculty appointment in physics and is a Center for Materials Research Scholar.
“A perovskite is a building block that has special properties and properties you can design just by choosing the right atom to put in it,” Brillson says, “and these can make sensors and computing elements.”
Depending on the atomsselected, these perovskites can sense temperature, pressure, magnetic field and voltage. When they are sandwiched around atomically-thin slabs of insulators, they can form ultrafast computer circuits. Just like ceramics used for cooking or re-entry vehicles for space shuttles, these perovskites can withstand very high temperatures of up to 1,000 C without burning because they’re already oxidized, and they retain their properties at high temperatures.
In addition to sensors for aircraft turbines, the perovskites could be used to make very sensitive phased array antennas — large checkerboards of tiny radar “dishes” that can triangulate signals to receivers, giving instantaneous positions of aircraft without the time delay encountered with rotating radar dishes.
“In order for each of these radar components to be sensitive enough, essentially all of the incoming electromagnetic waves must convert to electrical signals without producing heat, just the opposite of your microwave oven,” Brillson says. “But atoms in the materials used in antennas jiggle, especially at places in the crystals where the atoms are out of place.”
Many of these imperfections, which cause heating and “loss” of electrical signal, occur right at the interface between layers of these electromagnetic materials stacked together for high sensitivity and miniaturization. Using oxide molecular beam epitaxy, or MBE, a technique to grow crystals on a substrate, Brillson can “spray paint” atomic layers one at a time as a thin film on a wafer, carefully forming the perovskite crystals to minimize imperfections and allow electrons to pass through the layers with a particular spin. Spin is a property of electrons that a magnetic field can sense and that doubles the amount of information carried through an electrical circuit.
“My job is to understand how to make them perfect to less than a few parts per million,” says Brillson. “My interest is in surfaces and interfaces, so my research group has the tools to grow and analyze these on an atomic scale.”
Leonard Brillson,614-292-8015, firstname.lastname@example.org
On the Web: Center for Emergent Materials, cem.osu.edu