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

摘要

Guided by the tolerance factor and average electronegativity difference, two stable garnets with compositions Ca3BTiGe3O12 (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-3d space group was confirmed for synthesized compositions. A combination of microwave dielectric properties for both garnets suggested that Ca3MgTiGe3O12 ceramic possessed a much higher quality factor (Q x f) similar to 84 000 +/- 3000 GHz coupled by a higher dielectric constant (epsilon(r)) similar to 12.97 +/- 0.03, and a smaller temperature coefficient of resonance frequency (tau(f)) similar to -29.4 +/- 1.5 ppm/degrees C compared to its Zn counterpart (Q x f similar to 45 000 +/- 2000 GHz, epsilon(r) similar to 12.84 +/- 0.03, and tau(f) similar to -33.19 +/- 1.6 ppm/degrees 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.

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