エレクトロセラミックスに於ける応用鉱物学の実践―マイクロ波/ミリ波誘電体を例に = Practicing applied mineralogy on the electroceramics:examples: microwave and millimeter-wave dielectrics

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.抄録 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

Novel low-temperature sintering ceramic substrate based on indialite/cordierite glass ceramics

Abstract In this paper, a novel low-temperature sintering substrate for low temperature co-fired ceramic applications based on indialite/cordierite glass ceramics with Bi2O3 as a sintering aid showing low permittivity (εr) and ultralow dielectric loss (tan δ) is described. The fine powder of indialite was prepared by the crystallization of cordierite glass at 1000 °C/1 h. The optimized sintering temperature was 900 °C with 10 wt % Bi2O3 addition. The relative density achieved was 97%, and εr and tan δ were 6.10 and 0.0001 at 1 MHz, respectively. The composition also showed a moderately low temperature coefficient of relative permittivity of 118 ppm/°C at 1 MHz. The obtained linear coefficient of thermal expansion was 3.5 ppm/°C in the measured temperature range of 100 to 600 °C. The decreasing trend in dielectric loss, the low relative permittivity at 1 MHz, and the low thermal expansion of the newly developed composition make it an ideal choice for radio frequency applications

Micro/millimeter-wave dielectric indialite/cordierite glass-ceramics applied as LTCC and direct casting substrates:current status and prospects

Abstract Indialite/cordierite glass-ceramics demonstrate excellent microwave dielectric properties such as a low dielectric constant of 4.7 and an extremely high quality factor Qf of more than 200 × 103 GHz when crystallized at 1300°C/20 h, which are essential criteria for application to 5G/6G mobile communication systems. The glass-ceramics applied to dielectric resonators, low-temperature co-fired ceramic (LTCC) substrates, and direct casting glass substrates are reviewed in this paper. The glass-ceramics are fabricated by the crystallization of glass with cordierite composition melted at 1550°C. The dielectric resonators are composed of crystallized glass pellets made from glass rods cast in a graphite mold. The LTCC substrates are made from indialite glass-ceramic powder crystallized at a low temperature of 1000°C/1 h, and the direct casting glass-ceramic substrates are composed of crystallized glass plates cast on a graphite plate. All these materials exhibit excellent microwave dielectric properties

Volume crystallization and microwave dielectric properties of indialite/cordierite glass by TiO2 addition

Abstract Indialite/cordierite (Mg₂2Al₄Si₅O₁₈) glass-ceramics with a low dielectric constant of 4.7 and a high Qf of >200 × 10³ GHz are predicted for use as micro/millimeter-wave materials in the fifth generation (5G) mobile communication systems. The glass-ceramics have a serious cracking problem caused by the anisotropic crystal growth during the surface crystallization. In this paper, the cracking was prevented by adding TiO₂ which acts as a seed. The glass-ceramics produced without cracking were composed of spherical crystals of approximately 10 μm diameter, formed by volume crystallization. Precipitated phases of the glass-ceramics crystallized at 1200–1350 °C/10 h and 20 h were indialite, cordierite, Al₂TiO₅ and rutile. The glass-ceramics crystallized for 10 h were analyzed by the Rietveld method. Indialite precipitated as an intermediate metastable compound at the lower temperature of 1200 °C and transformed to cordierite at the crystallization temperature. The reaction between cordierite and TiO₂ produced the new Al₂TiO₅ phase. The amounts of Al₂TiO₅ and rutile affected the microwave dielectric properties. In particular, the amount of rutile affected the TCf. In the cases of 10 wt % added TiO₂, and the crystallized at 1250 °C for 10/20 h the TCf values were improved to -2/-8 ppm/°C