Changing to the next phase

Materials that change their phase in response to the electrical injection or extraction of an ionic species are harnessed in a wide range of applications, including batteries that can operate in a range of climates and smart windows that can control the amount of light or heat that passes through them. As Nianpeng Lu et al report, increasing the number of transferrable ionic species can greatly enhance the functionality of the system. Specifically, they report a material system in which the electrical insertion and extraction of oxygen (O^2-) and hydrogen (H⁺) ions can be independently controlled, giving reversible access to three distinct material phases that have very different optical, electrical and magnetic properties. This finding could further broaden the range of potential applications for phase-changing materials.