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<p>Low-permittivity microwave dielectric ceramics with nominal compositions Zn<sub>1.8-<i>x</i></sub>Co<sub><i>x</i></sub>SiO<sub>3.8</sub> (<i>x</i> = 0–0.12) were synthesized by a solid-state reaction route. The influence of Co<sup>2+</sup> substitution on phase evolution, lattice structure, densification behavior, and microwave dielectric performance was systematically evaluated. X-ray diffraction coupled with Rietveld refinement verifies that all specimens in the investigated range preserve a single-phase Zn<sub>2</sub>SiO<sub>4</sub> (willemite) solid-solution structure, with no detectable secondary phases. Microstructural observations indicate that a small Co<sup>2+</sup> addition facilitates mass transport along grain boundaries and assists pore removal, thereby enhancing densification at relatively low sintering temperatures. The composition with <i>x</i> = 0.04 exhibited the best overall performance, with a bulk density of 4.0893&#xa0;g/cm<sup>3</sup> and a relative density of 96.17%. At a resonant frequency of 13.121&#xa0;GHz, the dielectric properties were <i>ε</i><sub><i>r</i></sub> = 6.55, <i>Q</i> × <i>f</i> = 62,559.8&#xa0;GHz, and <i>τ</i><sub><i>f</i></sub> =  − 45.2&#xa0;ppm/℃. Meanwhile, the optimum sintering temperature was reduced to 1275 ℃. In contrast, further increasing Co content (<i>x</i> ≥ 0.06) introduces more grain-boundary imperfections and residual porosity, which compromises densification, decreases <i>Q</i> × <i>f</i>, and weakens the improvement in <i>τ</i><sub><i>f</i></sub>. Benefiting from the combination of low permittivity and high-quality factor, the developed Zn<sub>2</sub>SiO<sub>4</sub>-based ceramics show potential for high-frequency communication components. These results demonstrate that Co<sup>2+</sup> doping offers an effective pathway to achieve low-temperature densification while coordinating dielectric performance in willemite-type low-loss microwave ceramics.</p>

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Effect of Co2+ substitution on the phase evolution, densification behavior, and microwave dielectric properties of Zn1.8-xCoxSiO3.8 ceramics

  • 期刊论文

  • 发表日期：

    2026年5月24日

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

摘要

Low-permittivity microwave dielectric ceramics with nominal compositions Zn1.8-xCoxSiO3.8 (x = 0–0.12) were synthesized by a solid-state reaction route. The influence of Co2+ substitution on phase evolution, lattice structure, densification behavior, and microwave dielectric performance was systematically evaluated. X-ray diffraction coupled with Rietveld refinement verifies that all specimens in the investigated range preserve a single-phase Zn2SiO4 (willemite) solid-solution structure, with no detectable secondary phases. Microstructural observations indicate that a small Co2+ addition facilitates mass transport along grain boundaries and assists pore removal, thereby enhancing densification at relatively low sintering temperatures. The composition with x = 0.04 exhibited the best overall performance, with a bulk density of 4.0893 g/cm3 and a relative density of 96.17%. At a resonant frequency of 13.121 GHz, the dielectric properties were εr = 6.55, Q × f = 62,559.8 GHz, and τf =  − 45.2 ppm/℃. Meanwhile, the optimum sintering temperature was reduced to 1275 ℃. In contrast, further increasing Co content (x ≥ 0.06) introduces more grain-boundary imperfections and residual porosity, which compromises densification, decreases Q × f, and weakens the improvement in τf. Benefiting from the combination of low permittivity and high-quality factor, the developed Zn2SiO4-based ceramics show potential for high-frequency communication components. These results demonstrate that Co2+ doping offers an effective pathway to achieve low-temperature densification while coordinating dielectric performance in willemite-type low-loss microwave ceramics.