Dielectric response of ANb2O6 (A = Zn, Co, Mn, Ni) columbite niobates: From microwave to terahertz

In the upcoming 6-generation (6G) revolution, the achievement of low power consumption has become a key objective in research concerning terahertz devices. As an important component of passive devices, there are very few low-loss dielectric ceramics in the terahertz range. To elucidate the mechanism of loss and promote the application of microwave dielectric ceramics for future 6G technology (covering microwave and terahertz frequencies), the terahertz responses of ANb2O6 (A = Zn, Co, Mn, and Ni) columbite niobates were studied. The influences of magnetic loss on the Q×f values in the microwave range with different transition metal ions in the A-site were reasonably analyzed. Moreover, due to the weakened magnetic relaxation properties in the terahertz range, the samples all exhibited low loss and approximate transparency, especially for MnNb2O6 and NiNb2O6 (tanδ < 0.01 and absorption coefficient < 10 cm−1 below 1.2 THz), which subverted the definition of traditional low-loss microwave dielectric ceramics. Ultimately, based on Mie theory, we designed a prototypical broadband metamaterial reflector to validate the applicability of the ANb2O6 system in the terahertz band, which is highly important for the development of terahertz ceramic-based passive devices.