PNNL

Abstract

EXAFS and XANES were used to examine samples cubic ZrW2O8 and cubic ZrMo2O8 that had been pressure amorphized in a multi-anvil press and recovered to ambient conditions. Data were taken at the W LIII- and LI- or Mo K-edges, as well as at the Zr K-edge. These data indicate an increase in the average coordination number of tungsten in ZrW2O8 and a less pronounced increase in that of molybdenum in ZrMo2O8. This is in agreement with previous work. However, the Zr K-edge data indicated a, previously unreported, change in the average Zr-coordination from 6 to ~7 for both compounds. These results demonstrate that both the framework tetrahedra and octahedra distort on amorphization, and in the case of ZrMo2O8, the ZrO6 octahedra are more prone to distortion at the amorphization pressure. A decrease in the photoelectron scattering magnitudes for the metal-metal correlations was seen on amorphization, indicating that these correlations are less well defined in the amorphous material.