Dielectric and microwave properties of ZrO2 doped CaO-SiO2-B2O3 ceramic matrix composites

Research highlights: → In this study, we examine the ZrO2 as the sintering aid which can improve the sintering and dielectric properties. → We study the resultant dielectric and microwave properties at different sintering temperatures. → The CaO-SiO2-B2O3 ceramic matrix composites were synthesized by solid-phase method using (Ca(OH)2), silicic acid (H2SiO3) and H3BO3 as source materials with 0.3, 0.5 and 1.0 wt% of ZrO2. - Abstract: The behavior of dielectric and microwave properties against sintering temperature has been carried out on CaO-SiO2-B2O3 ceramic matrix composites with ZrO2 addition. The results indicated that ZrO2 addition was advantageous to improve the dielectric and microwave properties. X-ray diffraction (XRD) patterns show that the major crystalline β-CaSiO3 and a little SiO2 phase existed at the temperature ranging from 950 oC to 1050 oC. At 0.5 wt% ZrO2, CaO-SiO2-B2O3 ceramic matrix composites sintered at 1000 oC possess good dielectric properties: εr = 5.85, tan δ = 1.59 x 10-4 (1 MHz) and excellent microwave properties: εr = 5.52, Q . f = 28,487 GHz (11.11 GHz). The permittivity of Zr-doped CaO-SiO2-B2O3 ceramic matrix composites exhibited very little temperature dependence, which was less than ±2% over the temperature range of -50 to 150 oC. Moreover, the ZrO2-doped CaO-SiO2-B2O3 ceramic matrix composites have low permittivity below 5.5 over a wide frequency range from 20 Hz to 1 MHz.