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<p>Ca<sup>2+</sup>-doped Co<sub>1.1</sub>ZnTiO<sub>4</sub> ceramics (0 ≤ <i>x</i> ≤ 0.08) were successfully synthesized via the conventional solid-state reaction route to investigate the doping effects of Ca<sup>2+</sup> on their microwave dielectric properties. X-ray diffraction (XRD) results revealed a distinct crystal structure evolution: a single-phase spinel structure with the Fd-3m space group was maintained at <i>x</i> ≤ 0.04, while the CaTiO<sub>3</sub> secondary phase precipitated at <i>x</i> ≥ 0.06 due to the finite solid solubility of Ca<sup>2+</sup> in the matrix lattice. The optimal comprehensive dielectric performance was achieved at <i>x</i> = 0.04 sintered at 1175°C, achieving <i>Q</i> × <i>f</i> = 73,300&#xa0;GHz, <i>ε</i><sub><i>r</i></sub> = 21.46, and <i>τ</i><sub><i>f</i></sub> =  −17&#xa0;ppm/°C. Notably, H<sub>3</sub>BO<sub>3</sub> addition enabled a 275°C reduction in sintering temperature (down to 900°C) while retaining phase purity, which was fully confirmed by XRD analysis. Scanning electron microscopy (SEM) results verified improved bulk densification (relative density &gt; 93%) and uniform microstructures with a homogeneous grain size of approximately 2.5&#xa0;μm. Raman spectroscopy further indicated obvious [TiO<sub>6</sub>] octahedral distortion, and a redshift of the A<sub>1g</sub> mode from 720 to 715&#xa0;cm<sup>−1</sup> directly demonstrated lattice expansion after cation doping. The low-temperature-sintered samples at 900°C still exhibited competitive microwave dielectric properties (<i>Q</i> × <i>f</i> = 30,900&#xa0;GHz, <i>ε</i><sub><i>r</i></sub> = 20.21, <i>τ</i><sub><i>f</i></sub> =  −18&#xa0;ppm/°C), which strongly confirms that H<sub>3</sub>BO<sub>3</sub> serves as an efficient low-temperature sintering aid for the as-prepared titanate ceramics.</p>

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Synergistically Engineered Co1.1Zn0.9−xCaxTiO4 LTCC Ceramics via H3BO3-Assisted Sintering: Toward Enhanced Microwave Dielectric Performance

  • 期刊论文

  • 发表日期：

    2026年8月1日

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  • Xiaofei Shi,
  • Xi Wang,
  • Xinzhu Zheng,
  • Lei Wang,
  • Xiaoli Tang,
  • Hua Su,
  • Song Lizhong

摘要

Ca2+-doped Co1.1ZnTiO4 ceramics (0 ≤ x ≤ 0.08) were successfully synthesized via the conventional solid-state reaction route to investigate the doping effects of Ca2+ on their microwave dielectric properties. X-ray diffraction (XRD) results revealed a distinct crystal structure evolution: a single-phase spinel structure with the Fd-3m space group was maintained at x ≤ 0.04, while the CaTiO3 secondary phase precipitated at x ≥ 0.06 due to the finite solid solubility of Ca2+ in the matrix lattice. The optimal comprehensive dielectric performance was achieved at x = 0.04 sintered at 1175°C, achieving Q × f = 73,300 GHz, εr = 21.46, and τf =  −17 ppm/°C. Notably, H3BO3 addition enabled a 275°C reduction in sintering temperature (down to 900°C) while retaining phase purity, which was fully confirmed by XRD analysis. Scanning electron microscopy (SEM) results verified improved bulk densification (relative density > 93%) and uniform microstructures with a homogeneous grain size of approximately 2.5 μm. Raman spectroscopy further indicated obvious [TiO6] octahedral distortion, and a redshift of the A1g mode from 720 to 715 cm−1 directly demonstrated lattice expansion after cation doping. The low-temperature-sintered samples at 900°C still exhibited competitive microwave dielectric properties (Q × f = 30,900 GHz, εr = 20.21, τf =  −18 ppm/°C), which strongly confirms that H3BO3 serves as an efficient low-temperature sintering aid for the as-prepared titanate ceramics.