Crystallization behavior and properties of a novel rare-earth rich BaO–SiO2–La2O3 glass-ceramic for millimeter-wave technology

• Published in: Ceramics international 2022-10, Vol.48 (19), p.27913-27921
• Main Authors: Yang, Yanguo, Ren, Haishen, Peng, Haiyi, Xie, Tianyi, Zhang, Yi, He, Fei, Lin, Huixing
• Format: Article
• Language: English
• Subjects: Crystallization behavior; Dielectric properties; Millimeter-wave technology; Phase transformation; Rare-earth rich glass-ceramic
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2022.06.095

In this work, a novel low permittivity and high expansion coefficient rare-earth rich BaO–SiO2–La2O3 (BSL) glass-ceramic for millimeter-wave technology was systematically investigated by the network structure, crystallization the phase transformation, microstructure and microwave dielectric properties. With the decrease of the SiO2/BaO mol ratio from 3.75 to 0.9, the crystallization activation energy (Ec) of BSL glass calculated by the Kissiger equation continued to fall from 400.65 to 316.85 kJ/mol, and the crystal growth mode of all samples judging by Avrami parameter (n) was 1-D volume crystallization, implying that the crystallization ability of the BSL glass was enhanced. The main crystal phase of BSL glass-ceramic transformed from BaSi2O5 to BaSiO3 phase, coincided with a second phase Ba4La6O(SiO4)6. And then, the relative permittivity εr of BSL glass-ceramic had increased from 7.8 to 11, while quality factor (Q × f), temperature coefficient of frequency τf, and coefficient of thermal expansion (CTE) had decreased with the decrease of SiO2/BaO ratio. By adjusting the mol ratio of SiO2/BaO, the best comprehensive properties of 20BaO–75SiO2–5La2O3 glass-ceramic could be obtained with εr = 7.8, Q × f = 21000 GHz, CTE = 12.39 × 10−6/°C (30–800 °C), which was favorable properties for microwave dielectric applications.