Influence of Replacement of Silica by Various Glass-Forming Oxides on the Tendency to Phase Separation in the System R2O-B2O3-SiO2
The influence of equimolecular replacement of silica by ZnO, PbO, CaO, Al2O3, and GeO2 on the tendency of alkali borosilicate glasses to phase separation was studied. The original glass contained 4 mole% Li2O, 36 mole% B2O3, and 60 mole% SiO2. The influence of replacement of 5 mole% SiO2 by ZnO, CaO, PbO, and Al2O3, and of equimolecular replacement of up to 20% SiO2 by GeO2, on the tendency of the original glass to phase separation was investigated. The glasses were made at 1450–1500° in vitreous silica crucibles fitted with lids and molded into disks 30 mm in diamter and 4 mm thick, which permitted the most rapid cooling of the specimens to the annealing temperature. In addition, glasses in which SiO2 was replaced completely by ZhO, PbO, or GeO2 were investigated; these glasses were made at 900–950°, All the glasses were annealed at 400°. The glasses were investigated by the method of induced crystallization, by differential thermal analysis, and by determination of their electrical characteristics. The potentialities of this last method are discussed in the literature [1, 2]. The resistance was measured correct to 0.1 log ρ with aid of the E6–3 instrument, and dielectric losses were determined at 103Hz frequency with the MLE-1 instrument. The electrodes were attached by brazing with the silver paste.
KeywordsPhase Separation Differential Thermal Analysis Dielectric Loss Electrical Characteristic Consultant Bureau
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