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Detailed Program
Paper Number : EL-O07
Time Frame : 14:32~14:44
Presentation Date : Friday, 28, November
Session Name : Electronic Ceramics
Session Chair 1# : Eung Soo Kim
Session Chair 2# : Hisao Suzuki
Microstructure and Microwave Dielectric Properties of Zn1.8SiO3.8 Ceramics Prepared by Two-Step Sintering
Hong Jun Ahn
Kyonggi University
Keywords: Zn1.8SiO3.8, Two-step sintering, Dielectric properties, Willemite

The rapid progress in mobile and communication systems have increased the demand for the development of dielectric materials applicable to various devices working at microwave and millimeter wave. A low dielectric constant (K), a high-quality factor (Qf) and a near-zero temperature coefficient of resonant frequency (TCF) is necessary for these materials. Zn1.8SiO3.8 ceramics have been studied as a candidate material for advanced microwave applications because this ceramics prepared by conventional sintering method, exhibited good microwave dielectric properties. However, it is still needed to investigate the relationships between microwave dielectric properties and microstructural characteristics of Zn1.8SiO3.8 for the improvement of dielectric properties. Microstructural characteristics of ceramics could be controlled by sintering process.
In this study, the dependence of microwave dielectric properties of Zn1.8SiO3.8 ceramics on the two-step sintering was investigated. Single phase of willemite structure was confirmed for the Zn1.8SiO3.8 ceramics prepared by single-step and/or two-step sintering. Two-step sintering was composed of first step for grain growth and second step for densification. Densification temperature was selected at 1250oC which showed the maximum densification rate by dilatometry analysis.
The Qf value of the specimens with different holding time of densification temperature showed similar tendencies to the relative density of the specimens. For the specimens sintered at 1400oC for 5min and held at 1250oC for 4h to 12h, the Qf value showed the lower value than the specimens sintered at 1350oC for 5min and held at 1250oC for 4h to 12h. This result could be attributed to the higher density of specimens with 1350oC for 5min and held at 1250oC for 4h to 12h. Comparing to the specimens prepared by single step sintering, the specimens were prepared by two-step sintering showed the improved Qf value. For the specimens sintered at 1350oC for 5min and held at 1250oC for 4h, the Qf value showed the higher value (187,600GHz) than the specimens sintered at 1350oC for 4h. This result could be due to the densification of the specimens was successfully achieved. With increasing holding time, the Qf was decrease due to the increase of abnormal grain growth. However, similar K and TCF were obtained for the specimens prepared by single-step and/or two-step sintering.

References:

[1] Yiping Guo, Hitoshi Ohsato and Ken-ichi Kakimoto, J. Eur. Ceram. Soc. 26 (2006) 1827-1830.
Acknowledgements : This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology.