Microwave Dielectric Properties of β-CaSiO3 Glass–Ceramics Prepared Using Two-Step Heat Treatment

Jin-Seok Baek,Nak-Beom Jo,Eung-Soo Kim

doi:10.3390/pr9122180

Abstract

The microwave dielectric properties of β-CaSiO3 glass–ceramics are compared with those of α-CaSiO3 ceramics. β-CaSiO3 is prepared using glass–ceramics method with two-step heat treatment at 730 °C for 1–7 h and at 900 °C for 3 h, and α-CaSiO3 is prepared using conventional solid-state reaction and sintered at 1460–1500 °C for 3 h. With increasing holding time at 730 °C, the degree of crystallisation and Qf of the β-CaSiO3 glass–ceramics increased. The β-CaSiO3 specimens heat-treated at 730 °C for 3 h and 900 °C for 3 h exhibit the following dielectric properties: K = 6.57, TCF = −36.22 ppm/°C, and Qf = 52,400 GHz (highest) for the entire range of heat treatment conditions. The Qf difference between β-CaSiO3 and α-CaSiO3 could be explained by the bond characteristics using Rietveld refinement. FT-IR analysis shows that the Ca–O bond is the dominant factor for the Qf of CaSiO3 ceramics compared to the Si–O bond. The higher Qf of β-CaSiO3 than that of α-CaSiO3 can be attributed to the higher bond strength of Ca–O for β-CaSiO3 than that for α-CaSiO3.

Highlights

The fourth industrial revolution, which is the advancement of 5G telecommunication, Internet of Things (IoT), and automotive vehicles, typically requires high-frequency communication for integration and high performance of the future technologies
Lowtemperature co-fired ceramics (LTCC) dielectric materials can be incorporated into microwave devices for reducing their manufacturing cost [1,2]
Glass–ceramics prepared using two-step heat treatment are promising as LTCC substrate materials [5], in which the first step involves homogeneous formation of nuclei, and the second step involves the crystal growth of the nuclei [6]

Summary

Introduction

The fourth industrial revolution, which is the advancement of 5G telecommunication, Internet of Things (IoT), and automotive vehicles, typically requires high-frequency communication for integration and high performance of the future technologies. Β-CaSiO3 has SiO4 tetrahedral chain structure and α-CaSiO3 has three-membered SiO4 tetrahedral ring structure [8,9], and the dielectric properties of β-CaSiO3 and α-CaSiO3 prepared using conventional solid-state reaction are obtained at 16,850 and 42,200 GHz, respectively [10,11]. According to Mohammadi et al [12], the nucleation and crystallisation temperatures of β-CaSiO3 glass are 730 and 860 ◦C, respectively.

Results

Conclusion