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<p>In this study, a strategy involving the incorporation of non-adjacent valence state cations into tetrahedral sites was employed. Microwave dielectric ceramics with the composition Ca<sub>3</sub>M<sub>2</sub>Ga<sub>2.5</sub>V<sub>0.5</sub>O<sub>12</sub> (M=Sn and Zr) were designed and synthesized using a solid-state reaction method. The crystal structure of these ceramics has been verified as cubic garnet with the <i>Ia</i>-3<i>d</i> space group. Ca<sub>3</sub>Sn<sub>2</sub>Ga<sub>2.5</sub>V<sub>0.5</sub>O<sub>12</sub> and Ca<sub>3</sub>Zr<sub>2</sub>Ga<sub>2.5</sub>V<sub>0.5</sub>O<sub>12</sub> ceramics sintered at optimal temperatures exhibited favorable microwave dielectric properties, with <i>Q</i> × <i>f</i> values of 18, 571 GHz and 13,370 GHz, <i>ε</i><sub><i>r</i></sub> of 9.65 and 9.34, and <i>τ</i><sub><i>f</i></sub> values of − 43.1 ppm/°C and − 36.4 ppm/°C, respectively. The difference in <i>ε</i><sub><i>r</i></sub> is primarily attributed to the ionic polarizability per unit volume and bond ionicity. The higher <i>Q</i> × <i>f</i> value of the Ca<sub>3</sub>Sn<sub>2</sub>Ga<sub>2.5</sub>V<sub>0.5</sub>O<sub>12</sub> ceramic correlates with its larger packing fraction, narrower Raman full width at half maximum, stronger average bond covalency, and higher total lattice energy. In contrast, the smaller |<i>τ</i><sub><i>f</i></sub>| of Ca<sub>3</sub>Zr<sub>2</sub>Ga<sub>2.5</sub>V<sub>0.5</sub>O<sub>12</sub> is associated with its larger bond valence at the B-site, lower oxygen bond valence, and higher bond energy. Analysis using the Phillips−Van Vechten−Levine (P−V−L) theory and bond valence calculations demonstrates that the M<sup>4+</sup> cations occupying the octahedral sites have a significant impact on the microwave dielectric properties. Furthermore, a dielectric resonator antenna based on Ca<sub>3</sub>Sn<sub>2</sub>Ga<sub>2.5</sub>V<sub>0.5</sub>O<sub>12</sub> was designed for C-band communication (4−8&#xa0;GHz).</p>

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Crystal structure and microwave dielectric properties of two novel garnet-type ceramics with Ga3+/V5+ cations on tetrahedral site

  • 期刊论文

  • 发表日期：

    2026年6月23日

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  • Zehan Zheng,
  • Congxue Su,
  • Xiuzhen Wei,
  • Wenlong Tao,
  • Bochu Liu,
  • Sisi Pan,
  • Jun Fan,
  • Ruijuan Wang,
  • Liang Fang,
  • Huidan Lu

摘要

In this study, a strategy involving the incorporation of non-adjacent valence state cations into tetrahedral sites was employed. Microwave dielectric ceramics with the composition Ca3M2Ga2.5V0.5O12 (M=Sn and Zr) were designed and synthesized using a solid-state reaction method. The crystal structure of these ceramics has been verified as cubic garnet with the Ia-3d space group. Ca3Sn2Ga2.5V0.5O12 and Ca3Zr2Ga2.5V0.5O12 ceramics sintered at optimal temperatures exhibited favorable microwave dielectric properties, with Q × f values of 18, 571 GHz and 13,370 GHz, εr of 9.65 and 9.34, and τf values of − 43.1 ppm/°C and − 36.4 ppm/°C, respectively. The difference in εr is primarily attributed to the ionic polarizability per unit volume and bond ionicity. The higher Q × f value of the Ca3Sn2Ga2.5V0.5O12 ceramic correlates with its larger packing fraction, narrower Raman full width at half maximum, stronger average bond covalency, and higher total lattice energy. In contrast, the smaller |τf| of Ca3Zr2Ga2.5V0.5O12 is associated with its larger bond valence at the B-site, lower oxygen bond valence, and higher bond energy. Analysis using the Phillips−Van Vechten−Levine (P−V−L) theory and bond valence calculations demonstrates that the M4+ cations occupying the octahedral sites have a significant impact on the microwave dielectric properties. Furthermore, a dielectric resonator antenna based on Ca3Sn2Ga2.5V0.5O12 was designed for C-band communication (4−8 GHz).