Phase separation of glasses

Partitioning of gadolinium and its induced phase separation in sodium-aluminoborosilicate glasses

“…For the PA50 system, all Na cations should be stabilized by Al cations according to the acid-base reaction ranking previously discussed and local charge neutrality. 9 Based on the EDS analysis of the PA50Gd30 glass, the continuous phase contained about 10 mol% Al 2 O 3 that is assumed to be charge balanced by 10 mol% Na 2 O out of the total 11.58 mol% Na 2 O and the continuous phase was found to be enriched in Si based on EELS analysis of the analog of PA50Gd30 glass, i.e, PA50La30. Hence, the system may be reduced to close to a ÔB 2 O 3 -SiO 2 ' binary system 10 in which Gd cations ÔB 2 O 3 -SiO 2 ' binary system.…”

“…The T c and D increase as the z=r (or z=r 2 ) of the modifying cation increases [7]. Based on Debye-Huckel theory, by taking the degree of dissociation of cations in glass into account [4,9], a single master curve of T c versus z=ae (a ¼ distance between glass forming cation, tetrahedrally coordinated Si or B, and the nearest neighbor network modifying cation, and e ¼ dielectric constant) was demonstrated to exist for both silicate [9] and borate [10] systems exhibiting phase separation. This result supports the conclusion that phase separation originates from ionic interactions.…”

“…Negligible excess Na cations, or [Na 2 O] ex , (driven by thermodynamic equilibrium) are expected to be in the silicate-rich environments 9. A small amount of five-and six-fold Al is expected in the system even Na 2 O concentration is equal to Al 2 O 3 according to a recent highfield17 Al NMR study in silicate glasses[53].…”

Effect of alumina on enthalpy of mixing of mixed alkali silicate glasses

“…The addition of alumina to alkali silicate glasses reduces the number of non-bridging oxygen and is expected to affect the thermodynamic state of the glass. In fact, it is well known that alumina addition reduces the immiscibility tendencies of alkali silicate glasses greatly [9]. It is also known that the elimination of non-bridging oxygen of sodium silicate glass by the addition of alumina affects the sodium ionic mobility, producing a maximum in D.C. conductivity at the composition corresponding to Na/Al = 1, where no non-bridging oxygen is expected in the glass [10].…”

Evaluation of phase separation in glasses with the use of atomic force microscopy

“…Mazurin [2] references Shvetsov (1932) as publishing the first account of metastable immiscibility as a cause for chemical inhomogeneity in glasses. A number of review articles dealing with phase separation in glasses have been published, including frequently referenced publications by Mazurin [2,3], Tomozawa [4,5] Uhlmann [6] and James [7].…”