### Session Z31: Complexed Structured Materials, Glasses and Clathrates

11:15 AM–2:15 PM, Friday, March 17, 2006
Baltimore Convention Center Room: 329

Chair: M. J. Mehl, Naval Research Laboratory

Abstract ID: BAPS.2006.MAR.Z31.9

### Abstract: Z31.00009 : Raman scattering and modulated-DSC experiments on Potassium Germanate glasses*

12:51 PM–1:03 PM

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#### Authors:

N. Wang
D. Novita
P. Boolchand
(University of Cincinnati)

We have synthesized titled glasses in the 0 $<$ x $<$ 0.16 range by traditional melt-quenching, and have examined them in Raman scattering and modulated-DSC (MDSC) experiments. Raman lineshapes observed in the present work are quite similar to those reported by Henderson and Wang $^{1}$. Preliminary MDSC experiments reveal glass transition temperatures, T$_{g}$(x), starting from a value of 570\r{ }C at x = 0, to decrease to 508\r{ }C near x = 0.06, and to increase thereafter almost linearly to 552\r{ }C as x increases to 0.15. On the other hand, the non-reversing enthalpy associated with T$_{g}$ provides evidence of a global minimum in the 0.08 $<$ x $<$ 0.10 range, the reversibility window$^{2}$. These results are consistent with glasses at x $<$ 0.08 as \textit{Stressed-Rigid}, those at x $>$ 0.10 as \textit{Floppy,} while those in the reversibility window as representing the \textit{Intermediate Phase}$^{2}$. The space filling nature of the \textit{Intermediate Phase} is, independently, corroborated by trends in molar volumes which show a broad global minimum in the 9-11{\%} range. Identification of the three elastic phases provides a physical basis to understand the origin of the Germanate anomaly, and the electrical conductivity threshold when glasses become mechanically floppy. *Supported by NSF grant DMR 04-56472. $^{1}$ G.S.Henderson and H.M.Wang, Eur. J. Mineral. \underline {14}, 733 (2002). $^{2}$ P.Boolchand, G.Lucovsky, J.C. Phillips and M.F.Thorpe, Phil. Mag \underline {85},3823 (2005).

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.MAR.Z31.9