Phase Separation and Crystallization in Glasses of the Lithium
Silicate System xLi₂O (100 x)SiO₂ (x = 23.4, 26.0, 33.5)

G. A. Sycheva

Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences,
nab. Admirala Makarova 2, St. Petersburg, 199034 Russia

e-mail: Sycheva_galina@mail.ru

Received May 25, 2010

Abstract—The phase separation in ultimately homogenized glasses of the lithium silicate system
xLi₂O(100 – x)SiO₂ (where x = 23.4, 26.0, and 33.5 mol % Li₂O) has been investigated. The glasses of these
compositions have been homogenized using the previously established special temperature–time conditions,
which provide the maximum dehydration and the removal of bubbles from the glass melt. The parameters of
nucleation and growth of phase-separated inhomogeneities and homogeneous crystal nucleation have been
determined. The absolute values of the stationary nucleation rates I_st of lithium disilicate crystals in the
23.4Li₂O 76.6SiO₂ and 26Li₂O 74SiO₂ glasses with the compositions lying in the metastable phase separation
region have been compared with the corresponding rates I_st for the glass of the stoichiometric lithium disilicate
composition. It has been established that the crystal growth rate have a tendency toward a monotonic increase with
an increase in the temperature, whereas the dependences of the crystal growth rate on the time of low-temperature
heat treatment exhibit an oscillatory behavior with a monotonic decrease in the absolute value of oscillations. The
character of crystallization in glasses with the compositions lying in the phase separation region of the Li₂O–SiO₂
system is compared with that in the glass of the stoichiometric lithium disilicate composition. The inference has
been made that the phase separation weakly affects the nucleation parameters of lithium disilicate and has a
strong effect on the crystal growth.

Keywords: phase separation, crystal nucleation, stationary nucleation, crystal growth in phase-separated and
homogeneous glasses

DOI: 10.1134/S1087659611020155

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