Controlling the Phase Behavior of Low and Negative Thermal Expansion ReO-Type Fluorides using Interstitial Anions: ScZrF.

Density measurements suggest that the incorporation of ZrF into the cubic ReO-type structure of ScZrF is associated with the creation of anion interstitials. X-ray total scattering measurements are consistent with the conversion of corner-sharing octahedra to edge-sharing polyhedra as the solid solutions become richer in ZrF. The cubic (3̅) to rhombohedral (3) cooperative octahedral tilting transition seen for ScF moves to a higher pressure as increasing amounts of zirconium are added, and it is eventually suppressed completely ( = 0.