Science of tungstenbronze-type like Ba6–3xR8+2xTi18O54 (R=rare earth) microwave dielectric solid solutions

The crystallography of tungstenbronze-type like Ba6−3xR8+2xTi18O54 solid solutions for microwave dielectric materials applied for mobile phone and base station were studied. The crystal data and crystal structure of the fundamental lattice and supperlattice, and derivation of chemical formula and structural formula are summarized. Fourier map of the fundamental structure showed that oxygen ion positions of TiO6 octahedra were splitted. This fact proved the tilting of octahedra which is cause of superlattice. The mechanisms of microwave dielectric properties are summarized. Finally, guidelines for the design of the microwave dielectric materials are presented.