Low-temperature microwave and THz dielectric response in novel microwave ceramics

Low-temperature dielectric properties of BaZn1/3Nb2/3O3-based ceramics, CeO2-based ceramics and Ruddlesden–Popper Srn+1TinO3n+1 (n = 1–4) ceramics has been studied in microwave, THz and infrared frequency range down to 10 K. Extrinsic dielectric losses originating probably from diffusion of charged defects are observed in two families of compounds by a minimum in the temperature dependence of microwave quality Q. The rise of microwave permittivity and dielectric losses at low temperatures in Srn+1TinO3n+1 (n = 2–4) ceramics was explained by softening of an optical polar mode in SrTiO3, which is in the Srn+1TinO3n+1 (n = 3, 4) ceramics contained as a second phase.