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<p>SrAl<sub>2−<i>x</i></sub>(Mn<sub>0.5</sub>Mg<sub>0.5</sub>)<sub><i>x</i></sub>Si<sub>2</sub>O<sub>8</sub> (<i>x</i> = 0–0.06) microwave dielectric ceramics were synthesized via a solid-state reaction route. The sintering behavior, phase composition, microstructure, and microwave dielectric properties were systematically investigated by X-ray diffraction (XRD) with Rietveld refinement and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), together with microwave dielectric measurements. XRD–Rietveld refinement confirms that a single-phase monoclinic SrAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub> solid solution is maintained for <i>x</i> ≤ 0.02, whereas a Sr<sub>2</sub>MgSi<sub>2</sub>O<sub>7</sub> secondary phase appears for <i>x</i> ≥ 0.03 and increases with substitution, indicating the solubility limit of Mn/Mg co-substitution. The introduction of Mn/Mg effectively lowers the optimum densification temperature from 1500&#xa0;°C (<i>x</i> = 0) to 1350&#xa0;°C (<i>x</i> = 0.06). The composition <i>x</i> = 0.02 sintered at 1400&#xa0;°C for 5&#xa0;h exhibits the highest relative density (98.7%) and achieves a relative permittivity (<i>ε</i><sub>r</sub>) = 7.112, a quality factor multiplied by resonant frequency (<i>Q</i> × <i>f</i>) = 43,569&#xa0;GHz, and a temperature coefficient of resonant frequency (<i>τ</i><sub>f</sub>) =  − 37.8&#xa0;ppm/°C. When <i>x</i> &gt; 0.02, secondary-phase precipitation and microstructural inhomogeneity (as evidenced by SEM/EDS) reduce densification and lead to degraded dielectric performance, with <i>Q</i> × <i>f</i> decreasing to 28,800&#xa0;GHz at <i>x</i> = 0.06. These results clarify the solid-solution window and provide a feasible compositional strategy for lowering firing temperature while maintaining low-permittivity and low-loss performance in SrAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub>-based microwave dielectrics.</p>

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Effect of Mn/Mg co-substitution on the phase composition, microstructure, and microwave dielectric properties of SrAl2−x(Mn0.5Mg0.5)xSi2O8 ceramics

  • 期刊论文

  • 发表日期：

    2026年4月13日

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  • Jie Xu,
  • Yang Lu,
  • Heng Miao,
  • Huangping Yang,
  • Hongqing Zhou,
  • Huifen Lu,
  • Bo Zhang

摘要

SrAl2−x(Mn0.5Mg0.5)xSi2O8 (x = 0–0.06) microwave dielectric ceramics were synthesized via a solid-state reaction route. The sintering behavior, phase composition, microstructure, and microwave dielectric properties were systematically investigated by X-ray diffraction (XRD) with Rietveld refinement and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), together with microwave dielectric measurements. XRD–Rietveld refinement confirms that a single-phase monoclinic SrAl2Si2O8 solid solution is maintained for x ≤ 0.02, whereas a Sr2MgSi2O7 secondary phase appears for x ≥ 0.03 and increases with substitution, indicating the solubility limit of Mn/Mg co-substitution. The introduction of Mn/Mg effectively lowers the optimum densification temperature from 1500 °C (x = 0) to 1350 °C (x = 0.06). The composition x = 0.02 sintered at 1400 °C for 5 h exhibits the highest relative density (98.7%) and achieves a relative permittivity (εr) = 7.112, a quality factor multiplied by resonant frequency (Q × f) = 43,569 GHz, and a temperature coefficient of resonant frequency (τf) =  − 37.8 ppm/°C. When x > 0.02, secondary-phase precipitation and microstructural inhomogeneity (as evidenced by SEM/EDS) reduce densification and lead to degraded dielectric performance, with Q × f decreasing to 28,800 GHz at x = 0.06. These results clarify the solid-solution window and provide a feasible compositional strategy for lowering firing temperature while maintaining low-permittivity and low-loss performance in SrAl2Si2O8-based microwave dielectrics.