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Author: search.filters.author.Fang, LiangSubject: search.filters.subject.First principles

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    Structural and microwave dielectric properties of temperature-stable Ca1-xEuxMo1-xNbxO4 ceramics for dielectric resonator antenna applications
    (2025-10-15)
    Gu, Xiaolong
    ;
    Tang, Ying
    ;
    Wu, Jiangtao
    ;
    Zhang, Ning
    ;
    Zhang, Siying
    Ca<inf>1-x</inf>Eu<inf>x</inf>Mo<inf>1-x</inf>Nb<inf>x</inf>O<inf>4</inf> (0.1 ≤ x ≤ 0.7) ceramics were synthesized through the co-substitution of Ca<sup>2+</sup> and Mo<sup>6+</sup> in CaMoO<inf>4</inf> using Eu<sup>3+</sup> and Nb<sup>5+</sup>. All samples exhibited tetragonal scheelite structures within the range of 0.1 ≤ x ≤ 0.6. However, at x = 0.7, a monoclinic fergusonite structure was observed, as the [Nb/MoO<inf>4</inf>] tetrahedron at the B-site transforms into a [Nb/MoO<inf>6</inf>] octahedron. As the substitution amount increases, ε<inf>r</inf> (11.39–16.40), Q×f (21,950–82,930 GHz), and τ<inf>f</inf> (−47.72 to +8.01 ppm/℃) all show a gradual increase. Notably, the τ<inf>f</inf> value of this system can shift from negative to positive. The structural influence mechanism on the microwave dielectric properties in Ca<inf>1-x</inf>Eu<inf>x</inf>Mo<inf>1-x</inf>Nb<inf>x</inf>O<inf>4</inf> ceramics was clarified through various analytical methods, including ion polarizability, P-V-L chemical bond theory, bond valence theory, density of states (DOS), and electron localization function (ELF). Additionally, a resonant antenna designed and simulated using Ca<inf>0.4</inf>Eu<inf>0.6</inf>Mo<inf>0.4</inf>Nb<inf>0.6</inf>O<inf>4</inf> meets the requirements for satellite communication.