Influence of Lithium Substitution for Zinc on Crystal Structure and Microwave Dielectric Properties of Willemite Li_2x Zn_2−x GeO₄

Abstract

Willemite ceramics have recently received considerable attention for microwave or millimeter-wave telecommunication because of their extremely high quality factor. Unfortunately, it suffers from difficulty in the formation of pure phase Zn2GeO4. Reducing ZnO content is favorable for its phase purification. In this work, an alternative method, introducing 2 Li to substitute Zn, was proposed to reduce the Zn content. Some Li2xZn2−xGeO4 ceramics were designed and fabricated. Limited solid solutions were revealed and single phase willemite-based ceramics were obtained when x ≤ 0.04, beyond which a Li-rich phase Li2ZnGeO4 appeared. Li substitution was also found not only reducing the densification temperature but also improving the relative permittivity and quality factor of Zn2GeO4 ceramics. The densification temperature of Zn2GeO4 ceramics was further reduced to 950 °C after 5wt.% B2O3 additives, rendering their potential applications in low-temperature devices.