Generally, on the repeating of lithia-silica glass, it starts to crystallize at the temperatures near or below the softening point to convert into the polycrystalline material without deformation (M. A. Matveev, V. V. Velya. Steklo i Keramika, 16 [10] 14 (1959)).
In the present study, various oxides were added as the third component to a lithia-silica glass of the composition, Li₂O 25, SiO₂ 75mol%, and their effects on the crystallization of the base glass on repeating were investigated.
It was found that there is a limit in the amount for each oxide, and the addition over the limit inhibits the crystallization of the glass giving rise to the deformation or surface crazing of the sample during repeating (Fig. 2 and Fig. 3). The limit of the amount of addition in mol%, for each of the oxides varied with the own property of the oxides as follows:
(1) For each of the series of alkali- and alkaliearth-oxide, which acts as the glass network modifier in the glass structure, the limit decreases with the increase of the size of cation, i.e.,
The value of limit: NaO_0.5>KO_0.5>RbO_0.5, MgO>CaO>SrO>BaO.
For the oxides with the cation of about the same size but of the different valency, the oxide with the cation of the higher valency has always the higher limit, i.e.,
The value of limit: CaO>NaO_0.5, SrO>KO_0.5, BaO>RbO_0.5
(Fig. 6 and Table 8).
(2) For the glass network formers (BO_1.5, AlO_1.5, PO_2.5 and AsO_2.5) and also for the imtermediates (BeO, PbO, CdO, ZrO₂, CeO₂, LaO_1.5) the limit was generally low compared with that for the glass network modifiers, with the exception for the oxides of transition element (TiO₂, MnO_1.5, VO_2.5, CrO_1.5, FeO_1.5, CoO, NiO) (Fig. 7 and Table 8).
The structural explanations were made of the above results in terms of the polarizing power, and the ability of strengthening the glass network, of the cation in the oxides introduced.