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Evidence for the Intermediate Phase in Bulk (K2O)x(GeO2) 1-xglasses and its consequences on Electrical and Thermal Properties

by Wang, Ninghua

Abstract (Summary)
Knowledge on elastic phase transitions is the key to understanding the basic structure and properties of network glass systems. Generally, one can classify the inorganic glasses into three distinct phases, flexible-intermediate-stressed rigid, based on coordinates of the Lagrangian bonding constrains per atom, nc. Optimally constrained networks are characterized as nc =3, and labeled as Intermediate Phase. Those having nc < 3 are structurally flexible and those with nc > 3 are stressed-rigid in nature. In Potassium Germante glasses, an Intermediate Phase is observed in these glasses in the composition range 4% < x < 9%, where glasses transitions become thermally reversing. Trends of glass transition temperature (Tg), specific heat jump (ÄCp) and non-reversing enthalpy at Tg, ÄHnr , are recorded. Raman and IR spectroscopies are applied on present glasses and an optical elasticity power-law is deduced in the intermediate phase. From electrical conductivity measurement two conclusions are derived: first, conductivity jumps concur near x = 4% and x = 9% at the elastic phase boundaries; second, conductivity increase as a power-law in flexible glasses(x > 9%). Molar volume show a minimum when glasses enter the flexible phase. Present thermal, optical, electrical and mechanical experiments suggest that the Germanate Anomaly a result of the Intermediate Phase. However, connections to theory and fine structure in local and medium ranges are open to discussion.
Bibliographical Information:

Advisor:

School:University of Cincinnati

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:germanate anomaly potassium glasses intermediate phase mdsc

ISBN:

Date of Publication:01/01/2007

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