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

Abstract

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 × f) ∼ 84 000 ± 3000 GHz coupled by a higher dielectric constant (εr) ∼ 12.97 ± 0.03, and a smaller temperature coefficient of resonance frequency (τf) ∼ −29.4 ± 1.5 ppm/°C compared to its Zn counterpart (Q × f ∼ 45 000 ± 2000 GHz, εr ∼ 12.84 ± 0.03, and τf ∼ −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.

Lithium‐based batteries, history, current status, challenges, and future perspectives

“…347 The garnet-type materials have a general formula of A 3 B 2 C 3 O 12 , where A, B, and C can adapt to different combinations of cations. 348 The NASICON-type materials are phosphate-based ion-conducting glass-ceramics with the general formula of AM 2 (PO 4 ) 3 , where A = Li, Na or K and M = Ge, Zr, or Ti. These materials have both good chemical stability and mechanical stability.…”

“…The perovskite‐type materials have a general formula of ABO 3 , where A is a cation element in the groups I, II, and III of periodic table and B is a cation of the d‐block element in the periodic table 347 . The garnet‐type materials have a general formula of A 3 B 2 C 3 O 12 , where A, B, and C can adapt to different combinations of cations 348 …”