Combined EXAFS and Neutron Diffraction study of the structure of superionic conducting glasses; AgI-AgPO3 and Ag2S-AgPO3

Bragg Institute, Australian Nuclear Science and Technology Organisation* National Nuclear Energy Agency, Tangerang 15314, Indonesia**
â—‹Abby Scott* Shane J Kennedy* Evvy Kartini**

Selective doping of silver phosphate glass (AgPO3) with metal halides, akali-oxysalts and other glass formers can strongly enhance its electric conductivity. Doping with AgI or Ag2S produces exceptionally conductive glass, largely via superionic conduction of silver ions (Ag+). In an effort to understand the mechanisms of superionic conduction, the local environment around Ag+ ions in these glasses has been extensively studied using a wide variety of diffraction and spectroscopic techniques. Unfortunately, due to the disordered nature of glass, no one experimental technique can unambiguously reveal the complete atomic structure.
Our own neutron diffraction study on AgPO3, AgI-AgPO3 and Ag2S-AgPO3 glasses (performed on the HIT-II spectrometer at the spallation neutron source at KEK, Japan) provided excellent information on the modifications to the phosphate network in the doped glasses, but was not able to unambiguously separate the Ag-O, Ag-Ag and Ag-I pair correlations.
Here we report an EXAFS investigation on the same glasses using the Australian National Beamline Facility at the Photon Factory, KEK, Japan. The study was performed at the Ag absorption edge. We compare and contrast the EXAFS with the neutron diffraction results, noting how incorporation of the EXAFS result aids in construction of a more detailed and more accurate model of the structure of these glasses.