ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 12, Number 2
JKCSEZ 12(2)
April 20, 1968 

The physico-chemical properties of nine selected thallium borosilicate glasses and other 21 supplementary compositions were investigated. Their composition-property curves are found to be in many respects analogous to those of other borosilicate glasses containing lithia, soda, and lead oxide. It is indicated that certain minima found in the composition-property curves of thallium borosilicate glasses might be caused by a change in boron coordination as has been observed to occur in the Na2O-B2O3-SiO2 glasses. Typical effects of thallium ions on the borosilicate glass are summarized as follows: 1) Addition of thallium ions increased density, refractive index, water solubility, linear coefficient of thermal expansion, and dielectric constant. 2) Increased concentration of thallium decreased the softening point of the glasses, caused fluorescence under ultraviolet radiation and smeared out the absorption edges up to 15μ in the infrared region. An extensive liquid immiscibility was found by replication electron microscope technique in the Tl2O-B2O3-SiO2 system. The immiscibility covers a composition range roughly from 55 wt. % Tl2O to the binary system B2O3-SiO2. By acid treatment, it was found that the immiscible glass consists of separate silica-rich and boron-rich phases.