Microwave Dielectric Properties of a Low‐Firing Ba 2 BiV 3 O 11 Ceramic

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Novel LiAl5−xZnxO8−0.5x microwave dielectric ceramics were synthesized through a solid‐state reaction route. Phase evolution of LiAl5−xZnxO8−0.5x was determined by XRD analysis. The XRD results indicated that the phase compositions had a P4332 space group when 0 ≤ x ≤ 0.2 and a spinel structure when 0.3 ≤ x ≤ 0.5. The dielectric constant (εr) of this series’ solid solutions decreased with the increase in Zn doping content, which was in good agreement with the Clausius‐Mossotti relation. Oxygen vacancy and the decreased degree of order degraded the quality factor (Q × f) of the two structures. The deterioration in quality factor was further verified by impedance spectroscopy. The temperature coefficient of the resonant frequency (τf) decreased with the increase in x and was correlated with the unit cell volume. Finally, CaTiO3 was used as a compensation material to obtain a near‐zero τf of the LiAl5O8 ceramic.

Section: Resultsmentioning

confidence: 99%

Phase evolution and microwave dielectric properties of novel LiAl₅₋_xZn_xO_8−0.5_x‐based (0 ≤ x ≤ 0.5) ceramics

Lan

et al. 2019

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“…Among them, Ba 2 LaV 3 O 11 has attracted extensive attention in recent years due to its excellent microwave dielectric properties (ε r = 12.8, Q × f = 31 800 GHz, and τ f = −14.0 ppm/°C), and low sintering temperature (840°C) . We also found that Ba 2 BiV 3 O 11 ceramic could be densified at 870°C and possessed good microwave dielectric properties with ε r = 14.2, Q × f = 68 700 GHz, and τ f = −81.0 ppm/°C . This stimulates us to investigate whether other compounds in Ba 2 LnV 3 O 11 system exhibit good microwave dielectric properties.…”

Section: Introductionmentioning

confidence: 75%

Low‐firing and temperature stable microwave dielectric ceramics: Ba₂LnV₃O₁₁ (Ln = Nd, Sm)

Xiang

et al. 2017

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Low‐firing and temperature stable microwave dielectric ceramics of Ba2LnV3O11 (Ln = Nd, Sm) were prepared by solid‐state reaction. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the phase purity, crystal structure, sintering behavior, and microstructure. The XRD patterns indicated that Ba2LnV3O11 (Ln = Nd, Sm) ceramics belong to monoclinic crystal system with P21/c space group in the whole sintering temperature range (800°C ‐900°C). Both ceramics could be well densified at 880°C for 4 hours with relative densities higher than 96%. The Ba2LnV3O11 (Ln = Nd, Sm) samples sintered at 880°C for 4 hours exhibited excellent microwave dielectric properties: εr = 12.05, Q × f = 23 010 GHz, τf = −7.7 ppm/°C, and εr = 12.19, Q × f = 27 120 GHz, τf = −16.2 ppm/°C, respectively. Besides, Ba2LnV3O11 (Ln = Nd, Sm) ceramics could be well co‐fired with the silver electrode at 880°C.

“…An important factor which influences the dielectric constant in microwave dielectric ceramics is the average ionic polarizability (α theo / V m ) . And it can be determined by the modified Clausius‐Mossotti equation as follows:…”

Section: Resultsmentioning

confidence: 99%

High‐Q microwave ceramics of Li₂TiO₃ co‐doped with magnesium and niobium

et al. 2018

In order to solve the problems of acceptor/donor individual doping in Li2TiO3 system and clarify the superiority mechanism of co‐doping for improving the Q value, Mg + Nb co‐doped Li2TiO3 have been designed and sintered at a medium temperature of 1260°C. The effects of each Mg/Nb ion on structure, morphology, grain‐boundary resistance and microwave dielectric properties are investigated. The substitution of (Mg1/3Nb2/3)4+ inhibits not only the diffusion of Li+ and reduction in Ti4+, but also the formation of microcracks in ceramics, which promotes the enhancement of Q value. The experiments reveal that Q × f value of Li2TiO3 ceramics co‐doped with magnesium and niobium is 113 774 GHz (at 8.573 GHz), which is increased by 113% compared with the pure Li2TiO3 ceramics. And the co‐doped ceramics have an appropriate dielectric constant of 19.01 and a near‐zero resonance frequency temperature coefficient of 13.38 ppm/°C. These results offer a scientific basis for co‐doping in Li2TiO3 system, and the outstanding performance of (Mg + Nb) co‐doped ceramics provides a solid foundation for widespread applications of microwave substrates, resonators, filters and patch antennas in modern wireless communication equipments.