Quenchable high-density amorphous polymorphs of zirconium tungstate.

Zirconium tungstate turns amorphous above 2 GPa. Amorphous-Zr(WO(4))(2) is studied in situ using synchrotron x-ray diffraction and Raman spectroscopy at high pressure. The height and the position of the first peak of the structure factor as a function of pressure exhibit discontinuous changes suggesting an amorphous to amorphous transformation around 19 GPa. The pressure dependence of the Raman mode frequencies of the tungstate tetrahedra also exhibits a change at the same pressure. The high-density amorphous form appears to have higher oxygen coordination as compared to the low-density amorphous form.