Phase evolution, far-infrared spectra, and ultralow loss microwave dielectric ceramic of Zn2Ge1+xO4+2x (− 0.1 ≤ x ≤ 0.2)
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A series of willemite based ceramics Zn2Ge1+xO4+2x with − 0.1 ≤ x ≤ 0.2 were prepared by the solid-state reaction method. Influences of Ge nonstoichiometry on the crystal structure, densification, and microwave dielectric properties were evaluated in terms of X-ray diffraction, SEM, dielectric measurements and far-infrared spectra. Ge excess favored the formation of single-phase willemite but a high level of excess induced appearance of GeO2. In contrast, nominal composition and those with Ge deficiency comprised of ZnO and the willemite phase. Ge excess was found to be beneficial to the densification and dielectric properties optimization of Zn2Ge1+xO4+2x. A composition with x = 0.1 (Zn2Ge1.1O4.2) exhibited the optimum microwave dielectric properties with a relative permittivity εr ~ 7.09, a quality factor Q × f ~ 112,700 GHz (at 14.48 GHz), and a temperature coefficient of resonance frequency τf ~ − 51 ppm/°C.
This work was supported by Natural Science Foundation of China (Grant Nos. 21965009, 51502047, and 21761008), the Natural Science Foundation of Guangxi Zhuang Autonomous Region (Grant Nos. 2015GXNSFFA139003, 2016GXNSFBA380134, 2016GXNSFAA380018, and 2018GXNSFAA138175), and Project of Scientific Research and Technical Exploitation Program of Guilin (Grant No. 20170225). The authors would also like to thank the administrators in the IR beamline workstation of National Synchrotron Radiation Laboratory (NSRL) for their help in the IR measurement.
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