An in SituTemperature-Dependent Electron and X-ray Diffraction Study of Structural Phase Transitions in ZrV 2O 7

A detailed electron diffraction study has been made of the ZrV₂O₇member of theAM₂O₇family of displacively flexible framework structures and its temperature-dependent structural phase transformations. The phase below 77°C corresponds to a primitive 3×3×3 superstructure phase ofPaoverline3space group symmetry while the high temperature phase above 102°C corresponds to the normal parent structure. The intervening intermediate phase is a complex incommensurately modulated phase characterized by (more than one) incommensurate primary modulation wave-vector in the close vicinity of {1}/{3}<110>^*. The cubic point group symmetry of this intervening incommensurate phase is shown to be lowered from cubicm3m. No corresponding metrical strain distortion can be detected.