Correlation between dielectric constant and chemical structure of sodium silicate glasses

Journal URL: http://jap.aip.org/jap/staff.js

Fast-ion conduction and flexibility of glassy networks

We observe two thresholds in the variations of electrical conductivity of dry solid electrolyte (AgI)x(AgPO3)1-x glasses, when the AgI additive concentration x increases to 9.5% and to 37.8%. Raman scattering complemented by calorimetric measurements confirm that these thresholds are signatures of the rigidity phase transitions; at x = 9.5% from a stressed rigid to an isostatically (stress free) rigid phase, and at x = 37.8% from isostatically rigid to a flexible phase. In the flexible phase, the electrical conductivity seems to increase as a power of x, this is in good agreement with the theoretical prediction based on 3d percolation.Comment: Accepted by PR

Santorini volcano as a potential Martian analogue: The Balos Cove Basalts

The interpretation of geologic processes on Mars from sparse meteorite, remote sensing and rover data is influenced by knowledge gained from well-characterized terrestrial analogues. This calls for detailed study of candidate terrestrial analogues and comparison of their observable features to those encountered on the surface of Mars. We evaluated the mineralogical, geochemical, and physical properties of the Balos cove basalts (BCB) from the island of Santorini and compared them to Martian meteorites, Mars rover surface measurements, and other verified Martian analogues obtained from the International Space Analogue Rockstore (ISAR). Twenty rock samples were collected from the Balos cove area based on their freshness, integrity, and basaltic appearance in the field. Optical microscopy of BCB revealed a pilotaxitic to trachytic texture, with olivine and clinopyroxenephenocrysts in a fine groundmass of olivine, clinopyroxene, plagioclase, magnetite, and devitrified glass. All major minerals show normal zoning, including calcic plagioclase (An_(78–85) at the core and An_(60–76) at the rim), augite (En_(36-48)Wo_(41-44)Fs_(11–21)), and olivine (Fo_(74–88)). The dominant bands in the infrared-attenuated total reflectance (IR-ATR) spectra from BCB can be assigned to olivine (~875 cm−1), calcic plagioclase (~1130 cm^(−1)), and augite (~970 cm^(−1)). The whole-rock chemical compositions and mineralogy of the BCB are similar to published analyses of typical olivine-phyric shergottites and basalts and basaltic materials analyzed in Gusev and Gale craters on Mars. BCB porosity is in the range of 7–15% and is similar to the porosities of the ISAR samples. Although no terrestrial rock is ever a perfect match to Martian compositions, the differences in mineralogy and geochemistry between BCB and some classes of Martian samples are relatively subtle and the basalts of Santorini are as close a match as other accepted Mars basalt analogues. The Santorini site offers excellent field logistics that, together with the petrology of the outcrop, makes it a valuable locality for testing and calibration deployments, field training, and other activities related to current and future Mars exploration

Structural rearrangements and second-order optical response in the space charge layer of thermally poled sodium-niobium borophosphate glasses

Sodium-niobium borophosphate glasses have been thermally poled and studied in the mid- and far-infrared range to probe their possible structural rearrangements and to correlate them with the measured nonlinear optical (NLO) response. The infrared analysis of thermally poled and depoled glasses has revealed systematic structural changes in the NLO-active space charge layer at the anode on the basis of which we suggest that sodium ion migration from this layer is accompanied by an equivalent migration of oxide ions. Ion depletion in the NLO layer induces extensive, but partially reversible by depoling, modifications of the phosphate and niobate parts of the network that depend on the composition of the glass..

Structural Studies of Binary and Pseudo Binary Sodium-Borate Glasses of High Sodium Content

Journal URL: http://www.societyofglasstechnology.org.uk/cgi-bin/open.cgi?page=%20PC/PC-00a&sessionid=85597106; http://www.societyofglasstechnology.org.uk/cgi-bin/open.cgi?page=journal&sessionid=8559710