Structural Defects in Fused and Crystalline Silica

Abstract

SAMPLES of fused silica (optical quality from General Electric Co.) in the form of disks about 4 cm. diameter and 0.64 cm. thick were treated with a modification of an etchant material previously used for various types of soda-lime-silica glasses¹. In the modified solution the sodium ion was replaced by potassium. The composition of the etchant was 2.0 gm. potassium fluoride and 1.2 c.c. hydrochloric acid per 100 c.c. water. The flat surfaces of the disks were polished, and in initial etching treatments, it was observed that scratches and polishing defects were made visible. There was no evidence of flaw patterns on the polished surfaces characteristic of those found in soda-lime-silica glasses. In order to eliminate the effect of the polishing and surface treatments, the disks were split open and the fresh surfaces etched; the optimum time was about 24 hr.