Principal element design of garnets to access structure stability and excellent microwave dielectric properties

Guided by the tolerance factor and average electronegativity difference, two stable garnets with compositions Ca 3 BTiGe 3 O 12 (B = Mg, Zn) were designed, synthesized followed by structural, and dielectric characterization. The phase purity and structural characteristics were analyzed using X-ray, Rietveld refinement, and microstructural analysis through scanning electron microscopy. A cubic structure with an Ia- 3 d space group was confirmed for synthesized compositions. A combination of microwave dielectric properties for both garnets suggested that Ca 3 MgTiGe 3 O 12 ceramic possessed a much higher quality factor ( Q × f ) ∼ 84 000 ± 3000 GHz coupled by a higher dielectric constant ( ε r ) ∼ 12.97 ± 0.03, and a smaller temperature coefficient of resonance frequency ( τ f ) ∼ −29.4 ± 1.5 ppm/°C compared to its Zn counterpart ( Q × f ∼ 45 000 ± 2000 GHz, ε r ∼ 12.84 ± 0.03, and τ f ∼ −33.19 ± 1.6 ppm/°C). Such differences in dielectric performances were further explored utilizing packing fraction, ion polarizability, bond valence, Raman, and infrared spectrum to understand structure–property relationship.