Infrared and terahertz dielectric spectra of novel Bi2O3–Nb2O5 microwave ceramics

Microwave dielectric properties of fluorite-like (1 − x)Bi2O3–xNb2O5 solid solutions with various x between 0.1 and 0.26 are compared with complex dielectric response in THz and infrared frequency range between 0.1 and 100 THz, which allows the estimation of intrinsic and extrinsic dielectric losses. The best quality sample with the most attractive properties was found for x = 0.26 composition with the permittivity of 86, Qf = 1000 GHz and τf = 120 ppm/K. Our ceramic system exhibits two different crystal structures depending on Nb2O5 concentration and it is shown how the infrared reflectivity spectra can help to distinguish the structures. τf can be reduced to zero by mixing of Type II and Type III structures.