Density and Microhardness of Cu-As-Se Glasses

Abstract

Densities and Knoop hardnesses of As-Se and Cu-As-Se glasses were measured and correlated with the glass structure. On the As-Se binary system, the density and hardness were measured as functions of As content. In these curves, minimum points were found near 55-60 at% As, in addition to a well known maximum at 40 at% As. When Cu was added to the As-Se binary system, the minimum point in the As-rich region shifted toward the As-poor side. The compositions corresponding to the minimum, i.e. (55-60As, 40-45Se), (5Cu, 50As, 45Se) and (10Cu, 45-50As, 40-45Se), could be approximately connected by a line in Cu-As-Se diagram. This line divided the glass formation region of the Cu-As-Se system into two different glass structure regions. When Cu was added to As2Se3, both density and hardness increased with increasing Cu content, but the rate of increase changed at 15-20 at% Cu. In the As- and Cu-poor region, it is considered that Cu atoms added to the As-Se binary system fill up vacancies in the As-Se glass structure and increase the density. It is also stated that Cu results in Cu-Se bond, increasing the hardness. In the As- and Cu-rich region, metallic bond such as Cu-Cu is supposed to be formed. The structure having the metallic bond may be correlated to the peculiar phenomena, for instance, voltage controlled switching effect of the glass in this structure region.