Akinori Kan

Bio: Akinori Kan is an academic researcher from Meijo University. The author has contributed to research in topics: Dielectric & Solid solution. The author has an hindex of 22, co-authored 104 publications receiving 1604 citations.

Crystal structure of corundum type Mg4(Nb2–xTax)O9 microwave dielectric ceramics with low dielectric loss

Abstract: New microwave dielectric ceramics, i.e. Mg 4 (Nb 2− x Ta x )O 9 (MNT) solid solutions, were synthesized and their microwave dielectric properties and crystal structure were investigated in this study. From the discrete variational Xα (DV-Xα) method, it was found that the Ta–O bonds in the TaO 6 octahedron become more covalent than Nb–O bonds in the NbO 6 octahedron; this result leads to the decrease of the ionicity in the Ta 5+ ion. The dielectric constants of MNT were slightly decreased from 12.4 to 11.5; this result might be due to the covalent interaction of Ta–O bonding. The quality factors of the samples were found to exhibit high value ( Q · f ≒350 000 GHz for x =2) which is comparable to those of Al 2 O 3 .

Microwave dielectric properties of low-temperature sintered Mg3(VO4)2 ceramic

Abstract: In order to develop a new low-temperature co-fired ceramics (LTCC), the microwave dielectric properties and microstructure of (Mg 3− x Co x )(VO 4 ) 2 ceramics were investigated. The grain growth of Mg 3 (VO 4 ) 2 ceramic was observed as the sintering temperature was increased from 750 to 1050 °C; the maximum Q · f value of 65,440 GHz was obtained at the sintering temperature of 1050 °C. At a sintering temperature of 1075 °C, the Mg 3 (VO 4 ) 2 ceramic decomposed to form the MgO and liquid phases; the Q · f value of the sample decreased. As for the Co substitution for Mg, the XRPD patterns of (Mg 3− x Co x )(VO 4 ) 2 ceramics showed a single phase over the whole composition range; the individual curves indicated the maximum values for density which gradually converge as the sintering temperature is increased but the values shift toward the lower sintering temperatures with Co substitution for Mg. As a result, a Q · f value of 78,906 GHz with a dielectric constant of 9.5 was obtained at x = 2 when the sample was sintered at 900 °C for 5 h in air, whereas the temperature coefficient was −94.5 ppm/°C.

Microwave dielectric properties and crystal structures of spinel-structured MgAl2O4 ceramics synthesized by a molten-salt method

Abstract: The microwave dielectric properties and crystal structures of MgAl2O4 ceramics synthesized using either molten-salt (MA-M) or solid-state reaction (MA-S) methods were characterized in this study. Raman and 27Al solid-state nuclear magnetic resonance spectra indicated that Al3+ cations primarily occupied in tetrahedral sites of the MA-M ceramic. The degree of inversion x, i.e., degree of cation disorder in tetrahedral and octahedral sites, of the MA-M was higher than that of MA-S; such the preferential site occupation of Al3+ cations enhanced the covalency of the M O bonds in the MO4 tetrahedra (M = Mg and Al), leading to a decrease in the lattice parameters. The Q·f of the MA-M fired at 1600 °C was 201,690 GHz, while the MA-S synthesized at 1600 °C exhibited a Q·f of just 85,100 GHz. Based on these results, an intermediate spinel structure with a greater x evidently has a higher Q·f, and therefore the cation distribution is closely related to the Q·f of the ceramic.

Low loss dielectric materials for LTCC applications: a review

Abstract: Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The comme...

Improved thermal conductivity and dielectric properties of hBN/PTFE composites via surface treatment by silane coupling agent

Abstract: To achieve polymer-based composites for electronic packaging with low dielectric constant, low dielectric loss tangent and high thermal conductivity, silane coupling agent KH550 modified hexagonal boron nitride (hBN) platelets were introduced into PTFE matrix via a cold pressing and sintering method. The effect of surface treatment on the morphology, thermal conductivity and dielectric properties of the composites was investigated. The results revealed that after surface treatment, the interfacial adhension between hBN platelets and PTFE matrix was improved and the in-plane orientation degree of hBN platelets in PTFE matrix decreased, which effectively improvd the thermal conductivity of the composites. The thermal conductivity of hBN-KH550/PTFE composite with 30 vol% filler content is 0.722 W/mK, which is 2.7 folds of pure PTFE. Moreover, the enhanced interfacial adhension and reduced surface hydrophilicity of hBN platelets significantly decreased the interfacial polarization, resulting in not only lower dielectric constant and dielectric loss tangent but also weaker frequency-dependence.