Alumina‐silica Relationship in Glass*

Abstract

Assuming from a consideration of silicate minerals that aluminum should replace silicon in silicates, the authors investigated the system Naz0-Ca0-SiO~-Alz03. Densities and refractive indices have been determined and molecular refractions have been calculated. Partial molecular refractivities of & 0 3 indicate a coordination number of 4 for aluminum and deviate appreciably from values for compounds in which aluminum has a coordination number of 6. Interionic distances have been calculated for Si-0 and A1-0.As a result of these studies, it is concluded that the aluminum atom isomorphously replaces the silicon atom in the random fetrahedral network. With this replacement, Ca++ can increasingly replace Na+ in the interstices of the open structure.

The crystal and melt structure of spinel and alumina at high temperature: An in-situ XANES study at the Al and Mg K-edge

“…This agrees with the molar volume behavior of glasses and melts which is related to oxygen coordination. For several series of silicate glasses to which Al 2 O 3 was added, the partial volume increases linearly as a function of Al 2 O 3 content up to 40 cm 3 /mol (Stafford and Silverman, 1947). This volume is totally different to that observed at room temperature for a-Al 2 O 3 (corundum) equal to 25 cm 3 /mol, where Al occurs as [6] Al.…”

Structure, properties, and fabrication of calcium aluminate‐based glasses

“…In 1947, Safford et al investigated the interaction between Al 3+ and Si 4+ in glasses. Their study indicated that Al 3+ can play the role of the network former by virtue of isomorphic replacement with Si 4+ ion in the random tetrahedral configuration and the interstices of the open structure accommodate cations such as Na + and Ca 2+ .…”

Structural modification associated with Al2O3 addition in oxyfluoride glasses: Thermal and mechanical properties

“…3 In addition to different glass formers, numerous oxides of alkaline earth, heavy metal, and rare-earths along with their fluoride counterparts have been tried to formulate suitable host matrix to develop nano-crystalline alkaline-earth fluorides (CaF 2 , BaF 2 , SrF 2 ), heavy-metal fluorides (CdF 2 , PbF 2 ), alkaline earth/alkali-rare earth fluorides (BaGdF 5 , NaYF 4 ), etc. 10 On the other hand, it has also been reported that the presence of Al 2 O 3 in LiTaO 3 -SiO 2 glass system aids the crystallization process to obtain transparent glass-ceramics due to higher nucleation rate in terms of promoting phase separation in the glass-network. 4 In particular, when we look into the literature on various aluminosilicate-based oxyfluoride glass systems, a wide range of variation in Al 2 which yield transparent glass-ceramics containing fluoride nanocrystals.…”

“…9 Thus, inclusion of alumina in a silicate matrix may provide advantages like increased chemical durability, viscosity, hardness, thermal stability, and comparable thermal expansion properties. 10 On the other hand, it has also been reported that the presence of Al 2 O 3 in LiTaO 3 -SiO 2 glass system aids the crystallization process to obtain transparent glass-ceramics due to higher nucleation rate in terms of promoting phase separation in the glass-network. 11 Similarly, in Li 2 O-SiO 2 system, it has been observed that Al 2 O 3 simultaneously suppress the immiscibility temperature and promotes both crystallization process and liquidliquid phase separation.…”