Thermal expansion behavior of SrSiO3 and Sr2SiO4 determined by high-temperature X-ray diffraction and dilatometry

Abstract

Strontium silicates are widely known as high thermal expansion materials, especially from glass ceramic sealing applications. However, the thermal expansion behavior of the pure crystalline phases is still unknown. Hence, SrSiO 3 and Sr 2 SiO 4 were characterized with dilatometry and high-temperature X-ray diffraction. The measured coefficients of thermal expansion (CTE) of Sr 2 SiO 4 are strongly anisotropic and depending on the crystallographic direction vary between 3.9 and 16.6 9 10 -6 K -1 . SrSiO 3 has a somewhat higher isotropy of thermal expansion than Sr 2 SiO 4 . The CTE in the respective crystallographic directions differs by only 1.9 9 10 -6 K -1 . The mean CTE is between 10.9 and 12.8 9 10 -6 K -1 for SrSiO 3 and Sr 2 SiO 4 , respectively. A comparison of the Srphases with Ba-and Ca-phases with the same stoichiometry is given with respect to the crystal structures and the CTE.

Design and characterization of novel glass‐ceramic sealants for solid oxide electrolysis cell (SOEC) applications

“…On the other hand, thermal aging slightly increased the CTE of the HJ4 glass‐ceramic. This increase was probably due to an increase in the quantity of the SrSiO 3 phase having CTE of 10.9 × 10 −6 K −1 …”

“…SrO concentration was increased in HJ3 and further in HJ4 to have Sr containing crystalline phases in addition to having minimal SrO in the residual glass phase, thus maintaining a viscous glass behavior and to reduce the potential formation of Sr chromate. A proper balance of SiO 2 /SrO (equal to 1) is required to obtain a desired high CTE SrSiO 3 phase (10.9 × 10 −6 K −1 ), however, as the increasing of SrO contents also increases the possibility of formation of undesirable SrCrO 4 phase, improving one property could potentially come at the expenses of other functionalities, and the right balance is often difficult to achieve. Therefore, the SiO 2 /SrO in HJ3 and HJ4 was kept 2.3 and 1.99, respectively, slightly higher than some glasses reported in literature where formation of SrCrO 4 resulted in poor adhesion of glass‐ceramic with interconnects.…”

Shear Performance at Room and High Temperatures of Glass–Ceramic Sealants for Solid Oxide Electrolysis Cell Technology

“…The HJ4 system has SrSiO 3 as main crystalline phase having a CTE of 10.9 ×10 −6 K −1 [29], thus reducing localized stresses generation within the glass–ceramic. Anyway, the as-joined HJ4 glass–ceramic has a CTE of 9.3 ×10 −6 K −1 which is lower than that of Crofer22APU, therefore, it can lead to generate stresses at Crofer22APU/HJ4 glass–ceramic interface and make adhesive fracture more favorable under the externally applied load.…”

Glass‐Ceramics in the System BaO–SrO–ZnO–SiO2 with Adjustable Coefficients of Thermal Expansion

“…Most phases appearing in the above‐mentioned systems such as barium silicates exhibit high CTEs in the range from 10.3 to 16.9 × 10 −6 K −1 , depending mainly on the chemical composition but also on the microstructure . By analogy, also in the system SrO–SiO 2 high thermal expansion phases with CTEs in the range from 10.9 to 12.8 × 10 −6 K −1 have been reported . The only exception is the binary system ZnO–SiO 2 in which only one phase exhibiting a CTE of around 2.8 × 10 −6 K −1 exists .…”

“…1,6 By analogy, also in the system SrO-SiO 2 high thermal expansion phases with CTEs in the range from 10.9 to 12.8 9 10 À6 K À1 have been reported. 7 The only exception is the binary system ZnO-SiO 2 in which only one phase exhibiting a CTE of around 2.8 9 10 À6 K À1 exists. 8 This phase is known as a possible component of low thermal expansion materials.…”