Abstract

The author and his coleage have been studying electroceramics based on the applied mineralogy. The mineralogy has long history and has been the origin of all science. The material science is also based on the mineralogy. The author studied crystal structure analysis at the Mineralogical School of the University of Tokyo, and material science at the Department of Ceramics of Nagoya Institute of Technology, so he applied mineralogy to material science. He has been studying in following area: microwave dielectrics, millimeter-wave dielectrics, multilayer ceramic condenser, piezoelectric materials and so on. In this paper, pseudo-tungstenbronze dielectrics and homologous compound series on the microwave dielectrics and indialite/cordierite glass ceramics on the millimeter-wave dielectrics has been reviewed. The pseudo-tungstenbronze solid solutions have special point of x = 2/3 on the Ba₆₋₃xR₈+₂ₓTi₁₈O₅₄ (R = rare earth) that is the compositional ordering performed high quality factor based on the relationship between crystal structure and properties. Based on the knowledge of high Qf due to compositional ordering, new dielectrics with high Qf had been designed. On the homologous compounds, the relationship between the Qf properties and crystal structure due to substitute large cataion has been clarified for the design of base station resonator. On the millimeter-wave dielectrics, indialite glass ceramics are presented, which has low dielectric constant of 4.7 and extremely high Qf of more than 200 × 10³ GHz. It will be applied for resonators, patch antennas and LTCC substrates. The other materials such as multilayer capacitors and piezoelectric materials will be reviewed near future.