THE MICROSTRUCTURE OF BOROSILICATE GLASSES CONTAINING ELONGATED AND ORIENTED PHASE-SEPARATED CRYSTALLINE PARTICLES

The microstructure of phase-separated and stretched silver halide part icles, embedded in an aluminoborosilicate glass, is studied by small a ngle X-ray scattering. The data are quantitatively analysed, using a m odel of prolate ellipsoids of revolution generated by the elongation o f a distribution of spheres. The average particle is 22 +/- 3 x 160 +/ - 20 nm(2), but the distribution is very much skewed so that a fractio n of much longer particles is also present. Chemical reduction in hydr ogen causes the formation of metal particles inside the rigid glass ca vities formed during drawing. Two thirds of the volume of these caviti es remains empty, due to the loss of the halide atoms and to the highe r density of the silver crystals. The longer particles are lost, each one giving rise to two or three smaller ones. These data are compared with transmission electron microscopy (TEM) results. (C) 1998 Elsevier Science B.V. All rights reserved.