Microwave dielectric properties and microstructure of (Li₂Zn_3−xTi_4−xO_12−3x)–xCaTiO₃ ceramics (x = 0 to 0.32)

Abstract

In this paper, we investigated the effects of calcium contents on the sintering behaviors, phase composition, microstructure and microwave dielectric properties of Li₂Zn₃Ti₄O₁₂ (LZT) ceramics to find temperature stable and high quality factor (Q×f) microwave ceramics. The X-ray diffraction (XRD) results indicated the LZT and CaTiO₃ co-existed with each other and formed a stable composite system when the calcium was added. Scanning electron microscopy photographs also demonstrated the existence of CaTiO₃ phase, which were consistent with the XRD results. With the increasing calcium content, the apparent density decreased from 4.38 to 4.28 g/cm³, the dielectric constant (ε_r) increased from 19.3 to 23.9, Q×f decreased from 74344 to 42264 GHz, and the temperature coefficient of resonant frequency (τ_f) was significantly improved from −48 to +9.12 ppm/°C due to the increasing amount of CaTiO₃ phase. At last, the (Li₂Zn_2.72Ti_3.72O_11.16)–0.28CaTiO₃ ceramics sintered at 1200°C for 4 h displayed the excellent comprehensive properties of ε_r = 23.5, Q×f = 55604 GHz and τ_f = 0 ppm/°C.