Relationship between Rattling Mg2+ ions and anomalous microwave dielectric behavior in Ca3-xMg1+xLiV3O12 ceramics with garnet structure

Ca 3- x Mg 1+ x LiV 3 O 12 (0 ≤ x ≤ 1) ceramics with cubic-garnet-structure were synthesized by the solid-phase reaction. The replacement of Ca 2+ with the smaller Mg 2+ exerted an increasingly strong “rattling” effect at the A-site of Ca 3- x Mg 1+ x LiV 3 O 12 . With increased Mg 2+ , ε r increased from 10.5 ± 0.1 to 15.4 ± 0.1 and ε corr increased from 11.0 ± 0.1 to 16.0 ± 0.1, whereas the theoretical ε th decreased from 12.0 ± 0.1 to 10.5 ± 0.1. ε corr was higher than ε th due to the “rattling” effect. The enhanced “rattling” effect caused τ f to increase rapidly from –64.1 ± 1.0 ppm/°C to +267.2 ± 1.0 ppm/°C. With increased x , Q × f decreased from 74,700 ± 500 GHz to 15,370 ± 500 GHz, due to the decreased packing fraction, increased FWHM of the A 1g modes, and enhanced “rattling” effect. Additionally, the chemical compatibility between Ca 2.75 Mg 1.25 LiV 3 O 12 and Ag electrodes was confirmed, indicating this material’s potential for LTCC .