Issue 18, 2024

Influence of sintering characteristics and structural properties on the microwave dielectric properties of non-stoichiometric Ca3Mn2+xGe3O12+δ (x = 0–0.2) ceramics

Abstract

Low-K microwave dielectric ceramics are pivotal in 5G and millimetre-wave communications. Among them, garnet-structured ceramics hold significant strategic importance because of their rich elemental composition and high Q × f values. In this study, we investigated garnet-structured Ca3Mn2Ge3O12, aiming to optimize the ceramic phase composition through the synthesis of Ca3Mn2+xGe3O12+δ (x = 0–0.2) ceramics. XRD analysis revealed a pure phase of Ca3Mn2Ge3O12 (PDF#00-034-0285) only when x = 0.1, whereas impurity phases were observed for all other components. Rietveld refinement confirmed the garnet structure of the samples with the Ia[3 with combining macron]d space group. The highest bulk (4.383 g cm−3) and relative (96.34%) densities were achieved after sintering at 1190 °C, when the radial shrinkage reached 11.5%. At a sintering temperature of 1180 °C, the ceramics displayed excellent microwave dielectric properties: εr = 8.88, Q × f = 50 793 GHz, τf = −39.35 ppm °C−1. Raman, XPS, and Rietveld refinement data respectively revealed that the relative density of the ceramics was closely related to the dielectric constant; the relative Mn3+/Mn4+ content, packing fraction, and FWHM of the A1g Raman spectra were highly correlated with the Q × f value; and the Mn–O bond valence affected the Q × f and τf values of the samples. Furthermore, far-infrared reflectance spectroscopy indicated a theoretical Q × f value of ∼130 000 GHz, suggesting that the existing samples have potential for further development. In conclusion, Ca3Mn2+xGe3O12+δ (x = 0.1) ceramics with optimised phase compositions have great potential for development and application in 5G and millimetre-wave communications.

Graphical abstract: Influence of sintering characteristics and structural properties on the microwave dielectric properties of non-stoichiometric Ca3Mn2+xGe3O12+δ (x = 0–0.2) ceramics

Article information

Article type
Paper
Submitted
22 Feb 2024
Accepted
18 Apr 2024
First published
19 Apr 2024

J. Mater. Chem. C, 2024,12, 6615-6627

Influence of sintering characteristics and structural properties on the microwave dielectric properties of non-stoichiometric Ca3Mn2+xGe3O12+δ (x = 0–0.2) ceramics

Y. Liu, G. He, Y. Nie, W. Zhang, Z. Zhao and H. Zhou, J. Mater. Chem. C, 2024, 12, 6615 DOI: 10.1039/D4TC00698D

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