Heavy-metal oxide glasses might arbitrarily be defined as those containing over 50 cation percent of bismuth and lead which participate in the glass structure as network formers. Glass systems based on these heavy-metal oxides in silicates, borates, phosphates, germanates, and ferrites are surveyed. Gallate systems are emphasized since they have a unique ability to form stable glasses while maintaining key properties, such as the best infrared transmission and the highest nonlinear optical susceptibilities and diamagnetic Verdet constants for oxide glasses.

Heavy-Metal Oxide Glasses

Glass microspheres having an index of refraction of 2.7 or higher are prepared by (1) forming the microspheres from compositions based principally on 65-85 weight-percent Bi2 O3 and 5-35 weight-percent TiO2, and (2) rapidly heating the microspheres after they have been initially formed to cause an internal structural rearrangement that raises their index. Such microspheres are useful to form retroreflective products having superior properties and a more simplified construction.

Ultra-high-index glass microspheres and products made therefrom

This invention is directed to the preparation of glasses in the PbO--Ga 2 O 3 field exhibiting good infrared transmitting characteristics out to wavelengths of 8 microns. The binary glasses consist essentially, by weight, of about 15-28% Ga 2 O 3 and 72-85% PbO. However, the preferred glasses contain up to 85% Bi 2 O 3 and consist essentially as included within the area generally encompassed by the curve in FIG. 2.

Lead gallate glasses

This invention is concerned with the production of glasses in the Bi2O3-Ga2O3 system with, preferably, CdO which exhibit high indices of refraction and infrared transmitting capabilities to wavelengths of about 8 microns. The broadest scope of operable glasses involves, in weight percent, about -Bi2O3 40-90 -Ga2O3 5-30 -CdO 0-35 - with the preferred glasses consisting essentially of about -Bi2O3 55-85 -Ga2O3 7-17 -CdO 4-28 -

Bi2O3-Ga2O3 Glasses

This invention is directed to glasses exhibiting annealing points above 625° C., strain points above 600° C., linear coefficients of thermal expansion (25°-300° C.) below 90×10-7 /° C., refractive indices below 1.8, and, in thicknesses of 2 mm, infrared transmissions of at least 50% to wavelengths longer than 6 μm, consisting essentially expressed in terms of cation % on the oxide basis, of 5-40% KO0.5, 4-22% LaO1.5, 50-76% GaO1.5, and up to 15% total of at least one additional component in the indicated properties selected from the group consisting of ______________________________________ BaO 0-5 NaO0.5 0-5CaO 0-5 PbO 0-5CsO0.5 0-10 ZnO 0-5ReO1.5 0-5 Cl 0-5.______________________________________

Alkali metal lanthanum gallate glasses

Iron oxide is used to stabilize infrared transmitting, lead and cadmium bismuthate glasses. The resulting glasses contain, in cation percent, 8 to 80% Bi2O3, 0-57% PbO, 0-32% CdO, at least 5% Pbo + CdO, 5-32.5% Fe2O3, and 0-15% miscellaneous other oxides.

A Berleue

Papers

Stabilized bismuthate glasses