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<p>Ultra-low-temperature-sintered ceramics (ULTCCs) have attracted increasing attention owing to their excellent dielectric properties, low processing temperatures, and unique microstructures, which enable low dielectric loss in high-frequency applications. In this work, the dielectric behavior of Cu<sub>1−<i>x</i></sub>Ni<sub><i>x</i></sub>MoO<sub>4</sub> (CNMO, <i>x</i> = 0.02–0.11) ceramics was systematically investigated, with particular emphasis on the role of secondary phases. X-ray diffraction analysis revealed that samples with <i>x</i> = 0.02 and 0.08 were dominated by the CuMoO<sub>4</sub> phase, whereas Cu<sub>3</sub>(Mo<sub>2</sub>O<sub>9</sub>) and MoO<sub>3</sub> secondary phases emerged at <i>x</i> = 0.05 and 0.11, respectively. The formation of these secondary phases, together with changes in densification behavior, significantly modified both the dielectric permittivity (<i>ε</i><sub>r</sub>) and the quality factor (<i>Q</i> × <i>f</i>). SEM and EDS analyses confirmed distinct morphological and compositional features between the primary and secondary phases. The dielectric permittivity was mainly governed by shrinkage behavior and relative density, whereas <i>Q</i> × <i>f</i> was strongly influenced by the intrinsic loss characteristics of the secondary phases. The temperature coefficient of resonant frequency (<i>τ</i><sub>f</sub>) was primarily correlated with bond energy, bond valence, and thermal expansion behavior. Raman spectroscopy further revealed that shifts in Raman peak position and variations in the full width at half maximum (FWHM) of Mo–O vibrational modes were correlated with <i>ε</i><sub>r</sub> and dielectric loss. Among all compositions, Cu<sub>0.89</sub>Ni<sub>0.11</sub>MoO<sub>4</sub> ceramics sintered at 650&#xa0;°C exhibited optimal microwave dielectric performance, with <i>ε</i><sub>r</sub> = 4.61, <i>Q</i> × <i>f</i>  = 42,067&#xa0;GHz, and <i>τ</i><sub>f</sub> =  − 58.96&#xa0;ppm/°C. These results demonstrate that CNMO ceramics can achieve ultra-low-temperature sintering while maintaining excellent frequency stability and low dielectric loss, highlighting their strong potential for ULTCC and microwave communication applications.</p>

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Influence of secondary phases and Ni doping on the dielectric properties of Cu1−xNixMoO4 ceramics sintered at ultra-low temperature

  • 期刊论文

  • 发表日期：

    2026年1月3日

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  • Ling Tang,
  • Yuan-Bin Chen,
  • Ruihong Huang,
  • Yuedong Cai,
  • Jia-ao Yu

摘要

Ultra-low-temperature-sintered ceramics (ULTCCs) have attracted increasing attention owing to their excellent dielectric properties, low processing temperatures, and unique microstructures, which enable low dielectric loss in high-frequency applications. In this work, the dielectric behavior of Cu1−xNixMoO4 (CNMO, x = 0.02–0.11) ceramics was systematically investigated, with particular emphasis on the role of secondary phases. X-ray diffraction analysis revealed that samples with x = 0.02 and 0.08 were dominated by the CuMoO4 phase, whereas Cu3(Mo2O9) and MoO3 secondary phases emerged at x = 0.05 and 0.11, respectively. The formation of these secondary phases, together with changes in densification behavior, significantly modified both the dielectric permittivity (εr) and the quality factor (Q × f). SEM and EDS analyses confirmed distinct morphological and compositional features between the primary and secondary phases. The dielectric permittivity was mainly governed by shrinkage behavior and relative density, whereas Q × f was strongly influenced by the intrinsic loss characteristics of the secondary phases. The temperature coefficient of resonant frequency (τf) was primarily correlated with bond energy, bond valence, and thermal expansion behavior. Raman spectroscopy further revealed that shifts in Raman peak position and variations in the full width at half maximum (FWHM) of Mo–O vibrational modes were correlated with εr and dielectric loss. Among all compositions, Cu0.89Ni0.11MoO4 ceramics sintered at 650 °C exhibited optimal microwave dielectric performance, with εr = 4.61, Q × f  = 42,067 GHz, and τf =  − 58.96 ppm/°C. These results demonstrate that CNMO ceramics can achieve ultra-low-temperature sintering while maintaining excellent frequency stability and low dielectric loss, highlighting their strong potential for ULTCC and microwave communication applications.