ABSTRACT Lead‐free bismuthate‐based sealing glasses are of growing interest for environmentally sustainable electronic and packaging applications. In this work, lead‐free Bi 2 O 3 –ZnO–B 2 O 3 glasses were modified through two distinct substitution routes—BaO replacing B 2 O 3 and SrO exchanging for BaO—to evaluate their suitability for glass‐to‐metal sealing. BaO‐for‐B 2 O 3 substitution reduced glass transition temperature (330→325°C) and increased coefficient of thermal expansion (13.0→14.1 ppm/K) due to network depolymerization, yielding a low sealing range of 505–550°C, but decreasing nanohardness (4.9→4.6 GPa) and elastic modulus (69→63 GPa). SrO‐for‐BaO exchange maintained nearly constant density and mechanical properties, with only minor fluctuations in thermomechanical properties, while supporting a sealing window of 520–580°C. Raman spectra confirmed increasing nonbridging oxygen formation in BaO‐substituted glasses, whereas SrO exchange induced only subtle structural shifts. Both systems formed diffusion‐bonded interfacial layers (<2 µm) with 304 stainless steel and showed thermal expansion compatibility (mismatch <10%), validating hermetic sealing. These results establish BaO‐for‐B 2 O 3 substitution as advantageous for low‐temperature sealing and SrO‐for‐BaO exchange as beneficial for stabilizing thermomechanical properties, offering complementary design strategies for sustainable lead‐free sealing glasses.
Qin et al. (2026) studied this question.