Why does B₂O₃ suppress nepheline (NaAlSiO₄) crystallization in sodium aluminosilicate glasses?

Abstract

Addition of B2O3 in aluminosilicate glasses leads to structural changes that cause increase in liquidus viscosity and thereby suppresses crystallization.

Structural dependence of crystallization in phosphorus‐containing sodium aluminoborosilicate glasses

“…Although both the above-discussed models have high level of accuracy when predicting the formation of nepheline (>90%), they have been developed using small datasets of glasses (<1000 datapoints) with limited (and systematic) compositional variations. While there is an extensive dataset available in the literature covering the compositional space in sodium-and alumina-rich domain of borosilicate glasses doped with Li 2 O, CaO, Fe 2 O 3 , and B 2 O 3 , 1,2,7,[16][17][18][19][20][21] there is a severe scarcity of data pertaining to other oxides, for example, P 2 O 5 , K 2 O, and MgO.…”

“…The structure, viscosity, and crystallization behavior of the baseline glass have been discussed in our previous article. 20 While there is minimal literature about P 2 O 5 -containing alkali aluminoborosilicate glasses, the literature on P 2 O 5 -containing alkali borosilicate and alkali aluminosilicates, [23][24][25][27][28][29][30]35,37,40 , where z varies between 0 and 10 mol.%. An interesting point to note is that the P 2 O 5 -free baseline glass lies in the metaluminous, that is, Na/Al = 1 region of the alkali aluminosilicate system.…”

Structural drivers controlling sulfur solubility in alkali aluminoborosilicate glasses

“…38,81 Though previous studies 10 have highlighted that the presence of available voids aids in sulfur incorporation, it did not ensure a positive trend in the present investigation. This is interesting and its origins are likely attributed to the formation of 4-coordinated Al at the expense of non-framework Na + which imparts a higher rigidity to the glass structure as a result of the formation of Al−O−(Si, Al) directional bonds, 25,26 which then impedes the movement of sulfate units during its incorporation into borosilicate melts and thereby, suppressing sulfur loading in glassy matrix. This also indicates that the network polymerization is a predominant factor over available free space in terms of sulfur solubility.…”

“…While the first series comprises a total of three glasses in the composition regime ( The rationale behind the glass composition design is that a decrease in Na 2 O/Al 2 O 3 ratio will result in an increase in the polymerization in the glass network by reducing the fraction of non-bridging oxygens (NBOs) along with changes in boron coordination, as has been well reported in the literature. 25,26 On the other hand, substituting Na + by Li + in glasses is expected to alter the short-to-medium range ordering in the glass structure owing to the higher ionic field strength (IFS) of the latter (IFS: Li + = 0.26 Å −2 , Na + = 0.18 Å −2 ) (maintaining the fraction of NBOs constant since both the ions have +1 charge). [27][28][29][30] In both scenarios, based on the literature, the sulfur solubility in glasses is expected to decrease.…”

Nucleating role of P2O5 in nepheline‐based transparent glass‐ceramics

“…In recent years, much attention has been devoted to transparent glass-ceramics with higher strength, greater thermal, chemical stability, and wear resistance. [1][2][3][4] They have been widely used in many fields such as microwave compatible glass-ceramics (due to their low absorption of microwave energy), 5 astronomical telescope, 6 smart window, 7 band-pass filter, 8,9 and solar collectors. 10 Some of these glass-ceramics exhibit a fairly high crystalline content embedded in the residual glass matrix; nevertheless, they are fully transparent in the visible spectral range.…”