Phase evolution, thermal and microwave dielectric properties of cordierite-Al2O3 composite were investigated. As the content of Al2O3 increased, mullite, sapphirine, and spinel were formed as secondary phases, implying that cordierite may be decomposed by the reaction with Al2O3. All sintered specimens exhibited dense microstructures. The densification occurred through liquid phase sintering. As the content of Al2O3 increased, the thermal expansion coefficient and the dielectric constant increased, whereas the quality factor decreased. The thermal expansion coefficient, the dielectric constant, and the quality factor of the 90 wt% cordierite 10 wt% Al2O3 composite sintered at 1,425℃ were 2.9×10-6 K-1, 5.1, and 34,844 GHz, respectively.
We investigated the phase evolution, microstructure, and microwave dielectric properties of Na- and Zr-doped Ba(Mg0.5W0.5)O3 [i.e., (Ba1-2xNa2x)(Mg0.5-xZrxW0.5)O3] ceramics. BaWO4 as a secondary phase was observed in all compositions, and it increased as the dopant concentration increased. All specimens revealed a dense microstructure. For the composition of x=0.01, polyhedral grains were observed. As the dopant concentration increased, the densification and the grain growth were promoted by a liquid phase. The quality factor(Q×f0) decreased remarkably, whereas the dielectric constant (εr) tended to decrease as the dopant concentration increased. The dielectric constant, quality factor, and temperature coefficient of the resonant frequency of the composition of x=0.01 sintered at 1,700℃ for 1 h were 18.6, 216,275 GHz, and -22.0 ppm/℃, respectively.
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Structural, microstructural, opto-electronic and dielectric studies of Ba(Mg1-xZnx)1/2W1/2O3 (0.00 ≤ x ≤ 0.40) ceramics for dielectric resonators application Farhan Ullah, Asad Ali, Tanveer Ahmad, Salhah Hamed Alrefaee, Hala Siddiq, Farkhod Rakhmonov, Naseem Akhter, Vineet Tirth, Ali Algahtani, Abid Zaman Ceramics International.2026; 52(16): 31004. CrossRef
With trend of the miniaturization and the high-functionalizing of mobile communication system, low-loss microwave dielectric materials are widely used for high frequency communication components. These dielectric materials should be co-sintered with highly electric-conducting metal such as silver or copper for high-frequency and thick film process application. Sintering temperature of Ca[(Li1/3Nb2/3)1-xTix]O3-δ, which has excellent dielectric properties such as εr above 40, quality factor (Q·f0) above 16,000 GHz, and TCF (temperature coefficient of resonant frequency) of -20~-10 ppm/℃, is reported as high as 1,175℃, so it could not be co-sintered with silver or copper. Therefore in this study, low-temperature melting glasses of Zn-B-O and Zn-B-Si-O systems were added to Ca[(Li1/3Nb2/3)1-xTix]O3-δ to lower its sintering temperature under 900℃ without losing excellency of dielectric properties. With 15 weight % of Zn-B-Si-O glass and sintered at 875℃, specimen showed density of 4.11 g/cm3,ε r of 40.1, Q·f0 of 4,869 GHz, and TCF of -5.9 ppm/℃. With 15 weight % of Zn-B-O glass and sintered at 87 5℃, specimen showed density of 4.14 g/cm3, εr of 40.4, Q·f0 of 7,059 GHz, and TCF of -0.92 ppm/℃.
We investigated the physical properties of stoichiometric and non-stoichiometric oxide doped complex perovskite, Ba(Zn1/3Ta2/3)O3 ceramics and their impacts on the microwave dielectric performances using various characterization techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and network analyzer. According to the measurement of lattice constant changes, anomalous lattice volume contraction of ZrO2 doped Ba(Zn1/3Ta2/3)O3 sample only showed the dielectric quality factor enhancements, which was due to the lattice volume contraction as well as the 1:2 B-site cation ordering. In addition, NiO doping was useful to the stabilization of temperature coefficient of resonance frequency.
Microwave Dielectric Properties of the LiNb3O8-TiO2 Ceramic System with the Addition of Low Firing Agents Myung Ho Choi, Nam Chul Kim Journal of Korean Institute of Electrical and Electronic Materials Engineers.2008; 21(6): 517. CrossRef
A Study on the Enhancement of Cooling Efficiency for the Cabinet of Automatic Controller in the Interior of Industrial Building Soon-Ho Kim, Hyun-Jung Park Journal of the Korea Society For Power System Engineering.2013; 17(6): 79. CrossRef
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