Effect of K2O/SrO on structural, thermal, optical, and mechanical properties of SiO2–B2O3–SnO2 glass for IT/LT-SOFC applications

Abstract

A new series of borosilicate glasses (40SiO₂–15B₂O₃–(40 − x)K₂O–xSrO–5SnO₂, x = 0, 5, 10, 15, 20, 25, 30, 35, 40 mol%) are synthesized via a melt-quenching technique. X-ray diffraction of the as-prepared glasses confirmed the amorphous nature and phase separation in all the glasses. The phase separation tendency increases with the addition of SrO in place of K₂O in the glasses. Structural analysis revealed that with the sequential substitution of the monovalent K⁺ cation by the divalent Sr²⁺ cation, there was a significant effect on the silicate Qⁿ and borate BO₃ structural units. The optical band gap lies in the insulating range from 4.36 to 4.26 eV and decreases with SrO concentration, which makes the glasses good for use as sealants. The hardness was measured using Vicker’s indentation technique, and lies in the range of 5.4 to 7.0 GPa, comparable to other reported glass sealants. The thermal expansion coefficient (TEC) of the x = 20 and 25 glasses could be suitable for solid oxide fuel cell (SOFC) applications.