Phase purifying and dielectric improvement in Zn2SiO4 ceramics via simply controlling the particle size of SiO2

The zinc orthosilicate, Zn 2 SiO 4 ceramics, exhibit great potential as microwave dielectric materials due to their low dielectric constant and ultrahigh quality factor. The solid-state synthesis of Zn 2 SiO 4 ceramics often results in the presence of a secondary phase of ZnO, however, leading to significantly lower Q × f values. Cold-isostatic-pressing (CIP) and nonstoichiometry have been proven effective in purifying the Zn 2 SiO 4 but need elaborate process and composition manipulation. In this work, it was found that the particle size of SiO 2 plays a crucial role in purifying the Zn 2 SiO 4 phase. Specially, nano-sized SiO 2 particles (15 and 30 nm) led to the formation of a ZnO secondary phase in synthesized Zn 2 SiO 4 ceramics, while micro-sized (2 and 10 µm) resulted in pure-phase Zn 2 SiO 4 with excellent microwave properties. Notably, when prepared with 10 µm SiO 2 and sintered at 1 340°C, the resulting Zn 2 SiO 4 exhibited outstanding microwave performances with a Q × f value of 122 570 GHz, a temperature coefficient of frequency τ f of −51.9 ppm/°C, and a dielectric constant ( ε r ) of 6.5. These findings highlight the importance of controlling particle size during synthesis to achieve desired material properties such as purity and excellent microwave performances.