The influence of Cr2O3 on the temperature coefficient of linear expansion of glass in the oxide Na2O–B2O3–SiO2 system

In this study, the coefficients of linear temperature expansion (CLTE) of glasses were experimentally determined in the Na2O–B2O3–SiO2–Cr2O3 system with the following component contents (mol.%): 19.6–41.8 Na2O; 15.7–34.8 B2O3; 29.4–59.7 SiO2; and 0.5–2.0 Cr2O3. The CLTE (, К–1) of the investigated glasses in the temperature range of 20–4000C mainly depends on the content of Na2O, B2O3 and SiO2 oxides and can be quite accurately calculated by the following additive formula: , where [Na2O], [B2O3], [SiO2], and [Cr2O3] are the contents of respective oxides in the glass (mol.%). The accuracy of the calculations based on this formula is confirmed by a correlation coefficient of 0.995 between the calculated and experimental CLTE values of the studied glasses. Based on the additive coefficients, the degree of influence of the oxide components on the CLTE of the studied glasses was established in the following sequence: Na2O>Cr2O3>B2O3>SiO2. Despite the relatively high additive coefficient of Cr2O3, the partial influence of chromium (III) oxide on the CLTE of the studied glasses is small due to its relatively low content being within the range of 0.5–2.0 mol.%. The suggested calculation method can be uses in the development of new compositions of synthetic chrome aventurine glasses, crystalline ceramic glazes and enamel coatings.