An in situ temperature-dependent electron and x-ray diffraction study of structural phase transitions in ZrV2O7

A detailed electron diffraction study has been made of the ZrV2O7 member of the AM(2)O(7) family of displacively flexible framework structures and its temperature-dependent structural phase transformations. The phase below 77 degrees C corresponds to a primitive 3x3x3 superstructure phase of PA(3) over bar space group symmetry while the high temperature phase above 102 degrees 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 cubic m3m. No corresponding metrical strain distortion can be detected. (C) 1998 Academic Press.