Structure study of sodium disilicate glass in a Paris-Edinburgh cell using monochromatic x-ray diffraction and a multi-channel collimator

The ratio of non-bridging oxygen to tetrahedrally coordinated cation (NBO/T) represents the degree of polymerization and is one well-known way of structurally categorizing amorphous silicates. A number of studies show that at ambient temperature ultrasonic sound velocities (both longitudinal and transverse) of SiO₂ (Zha et al., 1994; Yokoyama et al., 2010; Kono et al., 2011) and other polymerized silicate glasses, including sodium disilicate which we recently studied (Yu et al., in prep), decrease with increasing pressure and reach minima between 2-3GPa, above which the velocities turn around and display a normal, positive pressure dependence. To systematically study the velocity profile of amorphous silicates and their relationship with the NBO/T value and detailed local structure, synthesized sodium disilicate glass was loaded into a Paris-Edinburgh (PE) cell to investigate pressure induced structure change using X-ray total scattering and pair distribution function (PDF) analysis at the GSECARS 13-ID-C beamline at the APS. X-ray diffraction data of the glass sample has been collected up to 3GPa at ambient temperature by utilizing a 60KeV monochromatic X-ray beam. We used a new multi-channel collimator (MCC; cf., Mezouar et al., 2002) to effectively remove unwanted scattering signal from the surrounding pressure media, and interfaced the Paris-Edinburgh cell (PEC) with the general-purpose diffractometer to decrease data collection time for glass structure measurement by more than one order of magnitude comparing with energy dispersive X-ray diffraction method. Results of our recent silicate glass structure measurements will be presented. We acknowledge the supports of COMPRES on facility development, of GSECARS and HPCAT for the Paris-Edinburgh press system.