Electronic polarizability in silicate glasses by comparison of experimental and theoretical optical basicities

Abstract

The concept of optical basicity proposed by Duffy has been recognized as an extremely important issue in science and technology of glasses. In this article, the refractive index (n o )-based optical basicity Λ(n o ) of some binary and ternary silicate glasses was evaluated using the Lorentz-Lorenz formula, and the discrepancy between the values of Λ(n o ) and the theoretically calculated optical basicity Λ th was analyzed to understand more deeply the electronic polarizability in binary and ternary silicate glasses. A suitable value of the optical basicity for each oxide predicting a good quantitative composition dependence of optical basicity in a given glass system was proposed. The suitable value of SiO 2 for the prediction of the optical basicity of silicate glasses is Λ(SiO 2 glass) = 0.53, which is larger than the value of Λ(SiO 2 oxide) = 0.48 being used in the calculation of Λ th so far. Other suitable values such as Λ(Al 2 O 3 glass) = 0.62 and Λ(TiO 2 glass) = 1.04 were proposed. The relationship between the optical basicity and coordination structure in some oxides in silicate glasses was discussed.

Composition–structure–property relationships of transparent Ca–Al–Si–O–N oxynitride glasses: The roles of nitrogen and aluminum

“…The results of Figure 6A,B reflect the dual effects of O and Si atoms being partially replaced by the more polarizable N and Al atoms, 72,91,92 respectively. Hence, the refractive index of the glass is enhanced when an Al or N atom is introduced, with the equal best-fit coefficients of Equation ( 8) suggesting equal contributions from both species.…”

Nanoscale composition fluctuations and crystallization process: Case study in Li2O–SiO2‐based glasses

“…62 The lithium silicate system has the largest immiscibility dome among the alkali silicate systems, 63,64 resulting in the limited homogeneous glass formation from SiO 2 to near the lithium disilicate Li 2 O⋅2SiO 2 compositions. The values of GFR, 62 ionic radius r + and field strength of R + ions, 65 singlebond strength B M-O in R-O bonds, 38 cation polarizability α i , [66][67][68] and optical basicity Λ of R 2 O [66][67][68] in binary R 2 O-SiO 2 system are summarized in Table 1 together with the data for SiO 2 . The field strength of a cation (F) was calculated using Dietzel's equation of F=Z c /(r c +r O2− ) 2 = Z c /a 2 , in which Z c is the valence of cation, and r c and r O2− are the radii of cation and oxide ion in Å units, respectively.…”

“…It is well known that alkali metal R + ions can move easily in glasses and SCLs and their diffusion coefficients are related to the size of R + ions, that is, smaller ionic radius, larger diffusion coefficient, Li + >Na + >K + 70–72 . The values of optical basicity also indicate that the chemical bond strength of Li + –O bonds is high compared with Na + /K + –O bonds 66–68 . Li 2 O and also Li + ions have, therefore, a smaller ionic radius, a larger diffusion coefficient, a higher field strength, and a stronger bonding strength compared with Na 2 O/Na + and K 2 O/K + , and these features would be closely related to the difference in GFR in the R 2 O–SiO 2 systems.…”

“…Ionic radius r + , field strength of a cation F, single-bond strength B M-O , cation polarizability α i , optical basicity Λ, GFR in binary R 2 O-SiO 2 systems, and the fraction of Q n species in R 2 O-2SiO 2 glasses38,[65][66][67][68]77,79,82 …”

“…On the other hand, R 2 O modifiers have low field strengths of F(Li 2 O) = .27, F(Na 2 O) = .18 Å −2 , and F(K Li + >Na + >K + [70][71][72]. The values of optical basicity also indicate that the chemical bond strength of Li + -O bonds is high compared with Na + /K + -O bonds [66][67][68]. Li 2 O and also Li + ions have, therefore, a smaller ionic radius, a larger diffusion coefficient, a higher field strength, and a stronger bonding strength compared with Na 2 O/Na + and K 2 O/K…”