Novel SrO-Containing Glass-Ceramic Sealants for Solid Oxide Electrolysis Cells (SOEC): Their Design and...

Area of Science:

• Materials Science
• Ceramic Engineering
• Solid Oxide Fuel Cell Technology

Background:

• Development of robust glass-ceramic sealants is critical for high-temperature applications like solid oxide fuel cells (SOFCs).
• Joining dissimilar materials such as Crofer22APU steel and yttria-stabilized zirconia (3YSZ) requires sealants with specific thermal and chemical compatibility.
• Strontium oxide (SrO) is explored as a key component to tailor sealant properties.

Purpose of the Study:

• To develop and optimize strontium oxide-containing glass sealants for joining Crofer22APU and 3YSZ.
• To investigate the effect of varying silicon oxide (SiO2), strontium oxide (SrO), calcium oxide (CaO), and aluminum oxide (Al2O3) on sealant properties.
• To evaluate the thermal, mechanical, and electrical performance of the developed sealants under simulated SOFC operating conditions.

Main Methods:

• Systematic variation of glass component oxides (SiO2, SrO, CaO, Al2O3) to create different sealant compositions.
• Characterization of crystallization behavior, coefficient of thermal expansion (CTE), adhesion, and reactivity with Crofer22APU.
• Long-term high-temperature testing (1000 hours at 850 °C) under dual atmosphere to assess stability and insulating properties.
• Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) for post-mortem microstructural and compositional analysis.

Main Results:

• Optimized glass sealant composition achieved a CTE in the 9.8-10.3 × 10^-6 K^-1 range, ensuring good compatibility with Crofer22APU and 3YSZ.
• The optimized sealant effectively hindered the formation of undesirable strontium chromate (SrCrO4) on the Crofer22APU steel after 1000 hours at 850 °C.
• High specific resistivity (approx. 10^6 Ohm.cm) was maintained at 850 °C, demonstrating excellent electrical insulation and stability under applied voltage.
• SEM-EDS analysis confirmed the absence of detrimental reactions between the glass-ceramic sealant and Crofer22APU under dual atmosphere conditions.

Conclusions:

• The developed SrO-containing glass-ceramic sealants are suitable for joining Crofer22APU and 3YSZ in high-temperature applications.
• The optimized sealant composition provides excellent thermal, mechanical, and electrical properties, crucial for SOFC performance and longevity.
• The study confirms the stability and inertness of the sealant in a dual atmosphere, preventing critical degradation pathways.