Effect of two-step sintering on the microwave dielectric properties of Zn1.8SiO3.8 ceramics

The microwave dielectric properties of Zn1.8SiO3.8 ceramics were investigated as a function of sintering conditions. A single-phase willemite structure was confirmed for Zn1.8SiO3.8 ceramics prepared by single-step or two-step sintering. In the two-step sintering, the first step was for grain growth and the second step was for densification. The densification temperature selected was 1250 °C, which showed the maximum densification rate by dilatometry analysis. Using two-step sintering, the specimens sintered at 1400 °C for 5 min and held at 1250 °C for 4–12 h showed a lower quality factor (Qf) than the specimens sintered at 1350 °C for 5 min and held at 1250 °C for 4–12 h. This result could be attributed to the higher density of the latter group of specimens. For the specimen sintered at 1350 °C for 5 min and held at 1250 °C for 4 h (two-step sintering), the Qf value was higher (187,600 GHz) than that of the specimen sintered at 1350 °C for 4 h (single-step sintering). However, all specimens showed quite similar dielectric constant (K) and temperature coefficients of resonant frequency (TCF).