AB2O4-type spinels with low relative permittivity (εr) and high quality factor (Q × f) are crucial to high-speed signal propagation systems. In this work, Zn2+/Ge4+ co-doping to substitute Ga3+ in ZnGa2O4 was designed to lower the sintering temperature and adjust the thermal stability of resonance frequency simultaneously. Zn1+xGa2−2xGexO4 (0.1 ⩽ x ⩽ 0.5) ceramics were synthesised by the conventional solid-state method. Zn2+/Ge4+ co-substitution induced minimal variation in the macroscopical spinel structure, which effectively lowered the sintering temperature from 1385 to 1250 °C. All compositions crystallized in a normal spinel structure and exhibited dense microstructures and excellent microwave dielectric properties. The compositional dependent quality factor was related to the microstructural variation, being confirmed by Raman features. A composition with x = 0.3 shows the best dielectric properties with εr ≈ 10.09, Q × f ≈ 112,700 THz, and τf ≈ −75.6 ppm/°C. The negative τf value was further adjusted to be near-zero through the formation of composite ceramics with TiO2.
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Chunchun Li gratefully acknowledges the financial support from the National Natural Science Foundation of China (No. 62061011), the Guangxi Zhuang Autonomous Region (Nos. 2018GXNSFAA281253 and 2019GXNSFGA245006), and the High-Level Innovation Team and Outstanding Scholar Program of Guangxi Institutes. The authors would also like to thank the administrators in the IR beamline workstation of the National Synchrotron Radiation Laboratory (NSRL) for their help in the IR measurement.
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Xiong, Y., Xie, H., Rao, Z. et al. Compositional modulation in ZnGa2O4 via Zn2+/Ge4+ co-doping to simultaneously lower sintering temperature and improve microwave dielectric properties. J Adv Ceram 10, 1360–1370 (2021). https://doi.org/10.1007/s40145-021-0511-0
- composition modulation
- dielectric properties