High Q Microwave Dielectric Ceramics in (Ni_1−x Zn_x)Nb₂O₆ System

Abstract

(Ni1−xZnx)Nb2O6, 0≤x≤1.0, ceramics with >97% density were prepared by a conventional solid‐state reaction, followed by sintering at 1200°–1300°C (depending on the value of x). The XRD patterns of the sintered samples (0≤x≤1.0) revealed single‐phase formation with a columbite (Pbcn) structure. The unit cell volume slightly increased with increasing Zn content (x). All the compositions showed high electrical resistivity (ρdc=1.6±0.3 × 1011Ω·cm). The microwave (4–5 GHz) dielectric properties of (Ni1−xZnx)Nb2O6 ceramics exhibited a significant dependence on the Zn content and to some extent on the morphology of the grains. As x was increased from 0 to 1, the average grain size monotonically increased from 7.6 to 21.2 μm and the microwave dielectric constant (ɛ′r) increased from 23.6 to 26.1, while the quality factors (Qu×f) increased from 18 900 to 103 730 GHz and the temperature coefficient of resonant frequency (τf) increased from −62 to −73 ppm/°C. In the present work, we report the highest observed values of Qu×f=103 730 GHz, and ɛ′r=26.1 for the ZnNb2O6‐sintered ceramics.

Effects of CuO additives and sol–gel technique on NiNb2O6 dielectric ceramics for LTCC application

“…The sintering temperature and density were 1275 ˚C and 5.603g/cm 3 (>99.5% theoretic density) respectively which are more or less the same with those reported by Liou et al [7] and Butee et al [21] and higher density than Lee et al [6].…”

“…However, Lee et al [6] got the highest quality factor Q׃ value 40100 GHz and the lowest sintering temperature 1150 ˚C with only 95% theoretic density which was lack of explanation. In this research, the quality factor Q׃ value for NiNb 2 O 6 reached 37500GHz which was nearly double more than those reported by Pullar et al [20], Liou et al [7] and Butee et al [21], and get closed to the result of Lee et al [6]. The dielectric constant was 22.1 and the temperature coefficient of resonant frequency was small negative as -30.4 ppm/˚C.…”

Correlation between microstructure and electrical conductivity in composite electrolytes containing Gd-doped ceria and Gd-doped barium cerate

“…The SEM images of all the composites were analyzed to find out the grain size distribution using Olysia m3 software (Olympus Corporation, Tokyo, Japan). 24 The backscattered images, from SEM, were processed using the software to improve the contrast for grain size analysis. For selecting the phases, manual as well automatic selection method was adopted.…”

Structure, dielectric properties, and applications of (Na0.5Sm0.5)TiO3-modified (Mg0.95Ni0.05)TiO3 ceramics at microwave frequency

“…It indicates that (Na 0. 5 matches the composition (x = 0.19) estimated using the mixing rule. With x = 0.19, the ceramic system shows a good temperature stability (t f = 1.1 ppm/ C).…”

“…The demand for developing new low-cost of microwave ceramics for such microwave communication applications must have a moderate relative permittivity (e r ), high dielectric Q Â f value (Q Â f > 5000 GHz), and temperature coefficient of resonant frequency close to zero (t f $ 0 ppm/_C) [1,2]. Moreover, a rapid growth of the cell phone and wireless communication markets in recent years has further led to extensive research and development in the area of microwave dielectrics with a high Q Â f [1][2][3][4][5][6][7][8][9][10].…”