Complex permittivity measurements of single-crystal and ceramic strontium titanate at microwave frequencies and cryogenic temperatures

The permittivity and dielectric loss tangent of bulk strontium titanate were measured from 4 to 300 K, at frequencies from 400 MHz to 3.8 GHz, using a dielectric rod-resonator technique. Single-crystal and ceramic SrTiO₃ samples were both investigated. Significant differences in permittivity and losses were observed between single-crystal and ceramic materials at cryogenic temperatures. When measured at liquid nitrogen temperatures, the single-crystal sample dielectric loss tangent was approximately 10^-4