Dielectric properties of MgO–ZnO–TiO₂-based ceramics at 1 MHz and THz frequencies

The dielectric properties (ε and tan δ) of MZT-based ceramics can be tailored at both 1 MHz and the terahertz (THz) frequencies (0.2–2 THz) by CaTiO₃ (CT) doping. CT was formed liquid phase during the sintering process and accelerated the densification of the ceramics. Doped with CT, the increase of the ε at 1 MHz could be explained by Lichtenecker expressions equation, and the tan δ is decreased at 1 MHz due to the high density. By doping with CT, the THz dielectric properties of ceramics can be modified, due to the variation of the lattice parameter and microstructure (porosity). At THz frequencies, ion displacement polarization is difficult to achieve, so that ε at THz is smaller than ε at 1 MHz according to Clausius–Mosotti equation. According to the four-parameter factorized oscillator model, the tan δ is increased with frequency up to THz frequencies. The power absorption of the MZT-based ceramics is lower than 10 cm⁻¹ below 1 THz, and it is a good choice as a transparent material at terahertz domain, which may promote the development of terahertz devices.