Negative thermal expansion and phase transition behaviour in Ag2O

The structure of Ag2O has been studied between 5 and 300 K using both high resolution synchrotron X-ray and neutron powder diffraction methods. Ag2O exhibits strong negative thermal expansion below 200 K and the cell volume is only weakly temperature dependent between 200 and 300 K. There is evidence for a first order phase transition below 35 K in Ag2O and this is apparently related to displacive disorder of the Ag cations. This disorder contributes to the observed NTE.