Switchable "hidden phase" could unlock useful properties

The term phase refers to an arrangement of atoms in a substance which gives it a certain set of properties. The most familiar phases are the three states of matter: solid, liquid and gas. But particularly in solids, there can be many more phases, characterised by distinctive crystal structures that lead to quite different materials. Ice, for example, has 10 distinct phases; there are many different phases of steel, and piezoelectric materials gained their ability to generate flows of current by switching between different phases in response to external stimuli.

A team from the University of Pennsylvania has discovered previously unknown phases "hiding" in the compound strontium titanate (SrTiO₃). Used in optical instruments, this material was already known to have unusual phase properties: it has a symmetrical, non-polar crystal structure that can be induced to switch into a different, polar (fractionally charged) phase by placing opposingly-charged ions along the long axis of its crystal.