Microwave dielectrics with enhanced permittivity

Depending on the operating frequency range of modern communication systems various microwave elements are required for effective microminiaturization of radio equipment. In this work potential ways of developing microwave dielectrics with high permittivity are discussed. In particular, it has been shown that temperature stable microwave dielectrics with a permittivity of about 100 can be developed by either influencing the phonon spectrum by means of aliovalent substitution in the cation sublattices or by the formation of a mobile cation sublattice. However, microwave dielectrics with permittivity above 100 require the employment of polarization mechanisms related with the spontaneously polarized state. In this case an increase in permittivity is generally accompanied by an increase in dielectric loss. Chemical systems demonstrating temperature stable properties are discussed, and include those in which an increase in permittivity is accompanied by relatively low dielectric loss. (c) 2005 Elsevier Ltd. All rights reserved.