Downloaded By: [Universidade est Campinas] At: 03:11 19 March 2008 Rntlrrriion Effects & DvJec1.s m Solrd.7, Vol 147, pp. 65 -71 Reprints available directly from the publisher Photocopying permitted by license only C 1998 OPA (Overseas Publishers Assoaauon) N.V. Published by license under the Gordon and Breach Science Publisher, Imprint. Piinled in India MICRON ORDER STRUCTURAL INHOMOGENEITIES IN VITREOUS SILICA OBSERVED BY ETCHING TECHNIQUE D.Y. OGATA*, A.H. SHINOHARA, D. TORIKAI and C.K. SUZUKI UNICAMP-University of Campinas, Faculty of’ Mechanical Engineering, Department of Materials Engineering, CP6122, CEP13081-970 Cumpinas-SP, Brazil (Received 12 December 1997) Etching of various vitreous silica samples over a long period (-2000min) with hydro- fluoric acid revealed a high contrast configuration of micron to sub-millimeter order boundaries similar to the grain boundaries of crystalline materials. In order to better understand this new result, various parameters, such as the vitreous silica preparation processes, the type of basic insume, the grain size of silica powder, the surface roughness, and the OH-content, were studied. They showed no correlation with the configuration of “amorphous-grain”. A possibility of an anisotropic micro-strain configuration induced by heterogeneous distribution of defects and impurities in the vitreous silica structure is suggested to explain the appearance of such grain boundary-like contrast. Keywords: Vitreous silica; Amorphous silicon dioxide; Chemical etching; Structural inhomogeneities I. INTRODUCTION Even though vitreous silica or amorphous silicon dioxide can appar- ently be considered a simple glass, the detailed structure of silica glass is still a subject of intense studies [l]. Various models to explain the structure of silica glass have been proposed. According to the con- tinuous random network model (CRN), the glassy structure is a tri- dimensional network, deficient in symmetry and periodicity [2]. In the * Corresponding author. E-mail: yogatap fem.unicanip.br. [421]/65