In　this　paper,　a　strategy　for　preparing　MgAl2-x(Mg0.5Ge0.5)xO4　(0　≤　x　≤　0.12)　solid　solution　ceramics　through　the　substitution　of　(Mg0.5Ge0.5)3+　for　Al3+　in　the　octahedral　lattice　of　spinel　crystal　structure　A(tetra)B2(octa)O4　via　traditional　high-temperature　solid-state　reaction　method　is　presented.　The　intrinsic　and　extrinsic　factors　influencing　their　microwave　dielectric　properties,　including　the　inversion　degree　of　A/B　lattice　sites　(lattice　occupancy),　bond　length　and　bond　valence,　as　well　as　grain　sizes,　were　investigated　using　Rietveld　refinement　of　X-ray　powder　diffraction　data　and　scanning　electron　microscopy.　To　verify　the　applicability　for　the　next-generation　5　G-n257/n258　millimeter　wave　frequency　band,　the　Q×f　values　were　tested　within　the　frequency　range　of　12–25　GHz.　Notably,　MgAl1.91(Mg0.5Ge0.5)0.09O4　ceramics　exhibited　a　high　Q×f　value　of　105,　384　GHz　@11.83　GHz,　low　Εr　of　8.7,　and　τf　of　−66.4　ppm/℃.　SrTiO3　was　added　to　tune　the　τf　to　a　near-zero　value　of　+2.6　ppm/℃　with　high　Q×f　value　of　51,　152　GHz　@11.53　GHz　and　Εr　of　9.91.　Finally,　a　microstrip　filter　with　a　center　frequency　of　3.6　GHz　was　designed　using　this　composite　ceramic,　successfully　demonstrating　its　practical　application　in　the　low-frequency　band　of　5　G　networks.　©　2024　Elsevier　Ltd