Water vapor sets some oxides aflutter

    Newly discovered phenomenon could affect materials in batteries and water-splitting devices.
    MIT Water Oxide Web
    These images, taken from a transmission electron microscope, show a perovskite material oscillating as it is exposed to water vapor and a beam of electrons. Image, courtesy of the researchers

    When one type of an oxide structure called perovskite is exposed to both water vapor and streams of electrons, it exhibits behavior that researchers had never anticipated: The material gives off oxygen and begins oscillating, almost resembling a living, breathing organism.

    The phenomenon was “totally unexpected” and may turn out to have some practical applications, says Yang Shao-Horn, the W.M. Keck Professor of Energy at MIT. She is the senior author of a paper describing the research that is being published today in the journal Nature Materials. The paper’s lead author is Binghong Han PhD ’16, now a postdoc at Argonne National Laboratory.

    When a particular kind of perovskite known as BSCF — after the chemical symbols for its constituents barium, strontium, cobalt, and iron — is placed in a vacuum in a transmission electron microscope (TEM) to observe its behavior, Shao-Horn says, “nothing happens, it’s very stable.” But then, “when you pump in low pressure water vapor, you begin to see the oxide oscillate.” The cause of that oscillation, clearly visible in the TEM images, is that “bubbles form and shrink in the oxide. It’s like cooking a polenta, where bubbles form and then shrink.”

    Read more at the MIT News Office.

    David L. Chandler | MIT News Office
    October 3, 2016