Application of a new necessary criterion for glass formation of one-component systems

摘要

Necessary conditions for glass formation by cooling melts are the presence of directed bonds and a sufficiently small temperature interval below the melting temperature, T_m, in which the atoms or constituents can rearrange to form crystallites. The corresponding temperature interval relative to T_m is estimated to be triangle open T_(min)/T_m= triangle open S_m/ ( 2C_(pl)-C_(ps) ) from the melting entropy, triangle open S_m and the specific heat capacities in the molten and the solid state, C_(pl) and C_(ps). This criterion has been applied to about 450 different one-component systems using literature data, compris-ing chemical elements, oxides, halides and chalcogenides as well as hard materials and intermetallics. The results are shown in detail and compared with information on the glass forming ability. Basically, new glass systems are not found beyond the vast empirical knowledge from the literature. However, the criteria help to understand the empirical results which systems form glasses and which do not. An important result for seeking new developments is to focus on eutectics of components with low triangle open T_(min)/T_m. Thus, the necessary criterion of low triangle open T_(min)/T_m helps to avoid unsuccessful research. According to the present review of data, glasses apparently cannot be obtained easily from one-component melts among the investigated borides, carbides, nitrides and silicides as well as intermetallics.