A low-firing melilite ceramic Ba 2 CuGe 2 O 7 and compositional modulation on microwave dielectric properties through Mg
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ISSN 2226-4108 CN 10-1154/TQ
Research Article
A low-firing melilite ceramic Ba2CuGe2O7 and compositional modulation on microwave dielectric properties through Mg substitution Changzhi YINa, c,†, Zezong YUb,†, Longlong SHUb, Laijun LIUc, Yan CHENa, Chunchun LIa,b,c,* a
College of Information Science and Engineering, Guilin University of Technology, Guilin 541004, China b School of Materials Science and Engineering, Nanchang University, Nanchang 330031, China c Guangxi Universities Key Laboratory of Non-Ferrous Metal Oxide Electronic Functional Materials and Devices, College of Material Science and Engineering, Guilin University of Technology, Guilin 541004, China Received: June 22, 2020; Revised: September 6, 2020; Accepted: September 15, 2020 © The Author(s) 2020.
Abstract: A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties. Sintered at 960 ℃, the Ba2CuGe2O7 ceramic had a high relative density 97%, a low relative permittivity (εr) 9.43, a quality factor (Q×f) of 20,000 GHz, and a temperature coefficient of resonance frequency (τf) –76 ppm/℃. To get a deep understanding of the relationship between composition, structure, and dielectric performances, magnesium substitution for copper in Ba2CuGe2O7 was conducted. Influences of magnesium doping on the sintering behavior, crystal structure, and microwave dielectric properties were studied. Mg doping in Ba2CuGe2O7 caused negligible changes in the macroscopic crystal structure, grain morphology, and size distribution, while induced visible variation in the local structure as revealed by Raman analysis. Microwave dielectric properties exhibit a remarkable dependence on composition. On increasing the magnesium content, the relative permittivity featured a continuous decrease, while both the quality factor and the temperature coefficient of resonance frequency increased monotonously. Such variations in dielectric performances were clarified in terms of the polarizability, packing fraction, and band valence theory. Keywords: ceramics; dielectric properties; melilite structure; compositional modulation
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Introduction
The development of wireless communication and broadband network technology has dramatically increased the demand for microwave dielectric materials,
† Changzhi Yin and Zezong Yu contributed equally to this work. * Corresponding author. E-mail: [email protected]
especially those being of small volume, low weight, high stability, and fast propagation speed [1,2]. The primary performance parameters that should be concerned are: (1) suitable relative permittivity εr depending on specific application scenarios, (2) high quality factors Q×f (or low dielectric loss), and (3) low-temperature drift of the resonance frequency (τf) [1–3]. Particularly, the official commercialization of the fifth-generation (5G) networks is expanding the operational frequency to microwave and millimeter
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J Adv Ceram 2020, 9(6): 0–0
waves, and even terahertz bands [4,5]. To
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