Ceramics-Silikáty 25, (1) 1 - 14 (1981)

In silicate glasses the boundary of anomalous changes is represented by trisilicate where the cross linked structure changes into a chain-linked one. An inversion occurs in the chemical resistance to water and acids, a deflection arises in the course of electrical conductivity. Metasilicate is a boundary of inverted glasses, which show an inverse change in the thermal expansion coefficient and tan δ at the point of this composition. In contrast to glasses Na₂O-B₂O₃, however, the coordination number remains unchanged. In alkali-alumina-silica glasses the geometrical properties are changed in relation to RM at the boundary Na₂O/Al₂O₃ = 1 : 1 when _<4>Al is changed to _<6>Al. The cause of the minimum of dielectric losses and that of the aluminoborate anomaly in relation to thermal expansion are discussed. With phosphate glasses, in the region of the ratio Na₂O : P₂O₅ = 1 : 1, the change in thermal expansion is similar to that of borates. Alkali phosphates in vitreous state differ from borates in the course of the elasticity modulus.