The relationship between the bond ionicity, lattice energy, bond energy and microwave dielectric properties of LaNbO 4 c
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The relationship between the bond ionicity, lattice energy, bond energy and microwave dielectric properties of LaNbO4 ceramics Mi Xiao1 · Yanshuang Wei1 · Qingqing Gu1 · Ping Zhang1 Received: 26 January 2018 / Accepted: 3 April 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018
Abstract LaNbO4 ceramics with single monoclinic fergusonite structure were prepared by the conventional solid-state reaction method at the sintering temperature range of 1275–1375 °C. The correlations of bond ionicity, lattice energy, bond energy and the microwave dielectric properties were investigated. The bond ionicity, lattice energy, and bond energy were calculated based on the complex bond theory to analyze the variation trend of dielectric constant (εr), the Q × f0 value and the temperature coefficient of resonant frequency (τf), respectively. LaNbO4 ceramics sintered at 1350 °C for 4 h possessed excellent microwave dielectric properties: εr = 21, Q × f0 = 55600 GHz and τf = 8 ppm/°C.
1 Introduction With the rapid development of electronic technologies, microwave materials are attracting more and more attentions [1, 2]. Microwave dielectric materials are very effective for miniaturizing devices and improving the packaging density of integrated circuits used in microwave band. Various microwave dielectric ceramics have been investigated which are widely used for devices such as resonators, filters, oscillators and antennas in the wireless communication system. To meet the requirements of these practical applications, three key factors of the ceramics need to be taken into account: relative high dielectric constant (εr) to reduce the size of devices, high quality factor (Q × f0) to meet the requirement of high working frequency of devices, and small temperature coefficient of resonant frequency (τf) to guarantee temperature stability [3, 4]. Numerous researches have been done to find materials with excellent microwave dielectric properties, and further studies are still in progress. Recently, Kim et al. reported that the LaNbO4 ceramics with a fergusonite-type structure (monoclinic, C2/c) * Mi Xiao [email protected] * Ping Zhang [email protected] 1
School of Electrical and Information Engineering & Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072, People’s Republic of China
presented good dielectric properties, and the sintering temperature could be reduced by adding sintering aids, for example, it could be reduced to 950 °C when L aNbO4 ceramics were doped with 3.0 wt% CuO, and enhanced microwave dielectric properties were obtained: quality factor (Q × f0) of 49,000 GHz, relative dielectric constant (εr) of 19.5, and temperature coefficient of resonant frequency (τf) of 1 ppm/°C [5, 6]. Some studies [7, 8] reported by Zhang and Zhao have shown that the microwave dielectric properties of rare earth ortho-niobates are greatly affected by the structural characteristics of the ceramics. However, the study on the relationships between th
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