Effect of Phase Separation on HF Etch Rate of Borosilicate Glasses

Etch rates of borosilicate glasses in HF were studied as a function of heat‐treatment time and temperature for liquid‐in‐liquid phase separation. It is shown that, when the phase‐separated glass has an interconnected microstructure, the composition of the chemically less durable phase is the dominant factor in HF durability. When the phase‐separated glass has a dispersed alkali‐borate‐rich (chemically less durable) phase embedded in a silica‐rich matrix, the HF etch rate is constant, independent of the extent of phase separation. Copyright © 1977, Wiley Blackwell. All rights reserved