Ceramics-Silikáty 24, (4) 289 - 319 (1980)

Alkaline binary and ternary systems exhibit an anomalous dependence of properties on composition, which varies with the individual network formers as well as with modificators. Most attention has so far been given to borate anomalies. The present paper is concerned with the study of chemical dependence of anomalies, using a comparative method on borate glasses (Part I), on silicate, alkali-aluminosilicate and phosphate glasses (Part II), and on germanate and tellurate glasses (Part III). A list of symbols employed in all the parts is enclosed to Part I. The phenomenological model has been studied within the entire range of the vitreous state in terms of the volume characteristics, of invariant points of phase equilibria, of thermochemical characteristics, and in particular in connection with boundaries of cross-linking. With the exception of the effect of combined isovalent ions a change in the „state" of oxygens has been found as the common feature of all the anomalies. The borate anomalies are spread all over the range of the vitreous state. However, they are concentrated above all at the relative standard compositions, in particular at that of pentaborate. The pentaborate ratio, which exhibits a minimum of thermal expansion, a minimum of tan δ, a minimum of activation energy of viscous flow, and a maximum of activation energy of the diffusion processes (chemical resistance) is considered to be related to the change from the ionic bond of oxygen atoms to a covalent one. In the transition between the two structures there appears the contact effect as the change in ionic vibration and that of Mie's indexes m and n, and the subsequent change in properties.