Surface modification of Zn2SiO4 starting powders for millimeter wave applications

Zinc silicate (Zn2SiO4) is a promising dielectric material for 5G communication substrates due to its low dielectric constant (εr = 6.1) and high-quality factor (Q.f = 219,000 GHz). However, its high sintering temperature limits its compatibility with the co-firing processes involving metal electrodes. This study aims to reduce the sintering temperature of Zn2SiO4 without the use of sintering aids and without deteriorating its dielectric performance. Spherical Zn2SiO4 powders were successfully synthesized using spray drying, with 1.00 M citric acid and the calcination temperature of 1350 °C. To further reduce the sintering temperature, the surface modification using 1.00 M acetic acid for 24 h was employed to induce the formation of amorphous surface layers. These layers, with the thickness of 42.39 ± 11.8 nm, promoted transient liquid-phase sintering, effectively enhancing mass transport and densification at the lower temperatures. Thermomechanical analysis indicated the maximum densification temperature of 1000 °C. Characterization and dielectric measurements confirmed phase purity and desirable microstructure. These findings demonstrated the method of lowering sintering temperature for the development of Zn2SiO4 ceramics tailored for next-generation wireless communication applications.