Growth Rate of Silver Halide Liquid Particles in an Alkali Alumino Borosilicate Glass

The growth rate of silver halide (AgX) liquid particles was measured in the alkali alumino borosilicate glass which could be converted to the photochromic glass with excellent light sensitive properties by appropriate heat treatment. The size of AgX liquid particles was mainly determined using X-ray line broadening technique assuming the size of liquid particles is equal to that of AgX crystallite found in quenched glass. Three compositions of particles, AgCl, AgClxBr1-x(x-0.79) and AgBr, were selected for measurement. The results were summarized as follows. (1) The maximum temperature below which the particles could deposit depended upon the composition of liquid. It was approximately 940°C in AgCl, 980°C in AgClxBr1-x(x-0.79) and 1080°C in AgBr, respectively. (2) Mean diameter of liquid particles of AgCl and AgBr increased in proportion to the cube root of heating time except initial period of time. In consequence the growth was considered to be performed according to the principle that larger particles grew by the dissolution of smaller ones. In case of AgClxBr1-x(x-0.79), the growth rate of liquid particles was smaller at lower temperature and larger at higher temperature than that expected from the cube root relation. (3) The growth rate for mean volume of liquid particles was approximately expressed by following equation, respectively. AgCl (510°-600°C) v/t=4.99×102exp-92500/RT (cm3⋅sec-1) AgClxBr1-x(x-0.79) (530°-700°C) v/t=1.00×102exp-96100/RT (cm3⋅sec-1) AgBr (585°-705°C) v/t=1.74×10-3exp-80000/RT (cm3⋅sec-1)