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<p>With the robust advancement of fifth-generation (5G) wireless communication and the steady progression of sixth-generation (6G) wireless communication toward practical implementation, the communication sector has imposed unprecedented requirements on microwave dielectric ceramics, particularly concerning their crucial performance parameters, including a suitable dielectric constant, ultra-low dielectric loss, and a near-zero temperature coefficient of resonant frequency. CoMo<sub>1-<i>x</i></sub>Te<sub><i>x</i></sub>O<sub>4</sub> (<i>x</i> = 0.01, 0.03, 0.05, 0.07) ceramics were successfully synthesized via the conventional solid-state reaction method. The mixed powders underwent pre-calcination at 500&#xa0;°C, and the samples were subsequently sintered for 4&#xa0;h within the temperature range of 550&#xa0;°C to 650&#xa0;°C. The results of X-ray diffraction (XRD) analysis and Rietveld refinement reveal that when <i>x</i> ≤ 0.03, the obtained samples are monoclinic ceramic crystals belonging to the <i>C</i>2/<i>m</i> space group. When the Te<sup>6+</sup> content <i>x</i> ≥ 0.05, a monoclinic crystal structure with the <i>P</i>2/<i>c</i> space group emerges. Moreover, at <i>x</i> = 0.07, the quality factor of the sintered ceramic samples reaches its maximum value at 600&#xa0;°C. According to scanning electron microscopy (SEM) analysis, the relative density has a significant impact on the dielectric constant and quality factor of the ceramics. Raman spectroscopy was utilized to probe the internal lattice vibration modes. The results demonstrate that the dielectric constant (<i>εᵣ</i>) of the ceramics exhibits a close correlation with the Raman spectral shifts, while the quality factor (<i>Q</i> × <i>f</i>) is strongly associated with the full—width at half-maximum (FWHM) of the Raman peaks. At 600&#xa0;°C, the CoMo<sub>1-<i>x</i></sub>Te<sub><i>x</i></sub>O<sub>4</sub> ceramics exhibit excellent dielectric properties: a dielectric constant <i>ε</i><sub><i>r</i></sub> = 9.13 (± 0.06), a quality factor <i>Q</i> × <i>f</i> = 84,224 (± 2301) GHz, and a temperature coefficient of resonant frequency <i>τ</i><sub><i>f</i></sub> = -72.8 (± 1.3) ppm/°C. The ionic polarizability and relative density are the primary determinants of <i>ε</i><sub><i>r</i></sub>. The <i>Q</i> × <i>f</i> is influenced by the packing density and relative density. Based on the P–V–L theory, the Mo–O bonds make a significant contribution to the quality factor (<i>Q</i> × <i>f</i>) and the temperature coefficient of resonant frequency (<i>τ</i><sub><i>f</i></sub>). Notably, at 600&#xa0;°C, the ceramics still maintain an appropriate dielectric constant (<i>ε</i><sub><i>r</i></sub>) and high-performance <i>Q</i> × <i>f</i> values. This research holds an indispensable role in the development of ultra-low temperature co—fired ceramics (ULTCC).</p>

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Effects of Te6+ substitution on the sintering behavior, phase composition, Raman characteristics, and microwave dielectric properties of CoMoO4 ceramics

  • 期刊论文

  • 发表日期：

    2025年10月19日

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  • Yuan-Bin Chen,
  • Ruxuan Tang

摘要

With the robust advancement of fifth-generation (5G) wireless communication and the steady progression of sixth-generation (6G) wireless communication toward practical implementation, the communication sector has imposed unprecedented requirements on microwave dielectric ceramics, particularly concerning their crucial performance parameters, including a suitable dielectric constant, ultra-low dielectric loss, and a near-zero temperature coefficient of resonant frequency. CoMo1-xTexO4 (x = 0.01, 0.03, 0.05, 0.07) ceramics were successfully synthesized via the conventional solid-state reaction method. The mixed powders underwent pre-calcination at 500 °C, and the samples were subsequently sintered for 4 h within the temperature range of 550 °C to 650 °C. The results of X-ray diffraction (XRD) analysis and Rietveld refinement reveal that when x ≤ 0.03, the obtained samples are monoclinic ceramic crystals belonging to the C2/m space group. When the Te6+ content x ≥ 0.05, a monoclinic crystal structure with the P2/c space group emerges. Moreover, at x = 0.07, the quality factor of the sintered ceramic samples reaches its maximum value at 600 °C. According to scanning electron microscopy (SEM) analysis, the relative density has a significant impact on the dielectric constant and quality factor of the ceramics. Raman spectroscopy was utilized to probe the internal lattice vibration modes. The results demonstrate that the dielectric constant (εᵣ) of the ceramics exhibits a close correlation with the Raman spectral shifts, while the quality factor (Q × f) is strongly associated with the full—width at half-maximum (FWHM) of the Raman peaks. At 600 °C, the CoMo1-xTexO4 ceramics exhibit excellent dielectric properties: a dielectric constant εr = 9.13 (± 0.06), a quality factor Q × f = 84,224 (± 2301) GHz, and a temperature coefficient of resonant frequency τf = -72.8 (± 1.3) ppm/°C. The ionic polarizability and relative density are the primary determinants of εr. The Q × f is influenced by the packing density and relative density. Based on the P–V–L theory, the Mo–O bonds make a significant contribution to the quality factor (Q × f) and the temperature coefficient of resonant frequency (τf). Notably, at 600 °C, the ceramics still maintain an appropriate dielectric constant (εr) and high-performance Q × f values. This research holds an indispensable role in the development of ultra-low temperature co—fired ceramics (ULTCC).