Tuning of microwave dielectric properties of garnets Ca3Mg2CV2O12 (C = Si, Ti) through compression and expansion effects

作者：Qiu, Huizi; Tang, Ying; Li, Jie; Xiang, Huaicheng^*; Fang, Liang^*

来源：Ceramics International, 2023, 49(1): 565-570.

DOI：10.1016/j.ceramint.2022.09.024

• Garnet-structure
• Dielectric properties
• Bond valence
• Rattling and compressed cations

Two novel low-er Ca3Mg2CV2O12 (C = Si, Ti) ceramics with the garnet structure were synthesized by a traditional solid-state reaction method. Rietveld refinements based on XRD patterns show both the compounds crystallized into a cubic structure with the Ia-3d space group. Outstanding microwave dielectric properties (er = 9.70, Q x f = 35,680 GHz, and tf = 60.1 ppm/degrees C for Ca3Mg2SiV2O12 ceramic; epsilon(r) = 11.70, Q x f = 48,530 GHz, and tf = 43.7 ppm/degrees C for Ca3Mg(2)TiV(2)O(12) ceramic) were obtained at 1240 degrees C and 1260 degrees C, respectively. The bond valence calculations reveal that Ca2+ at the A-site and Mg2+ at the B-site are slightly compressed, in combination with "rattling" Si4+ and "compressed" V5+ in the C-site of Ca3Mg2SiV2O12 compared to "rattling" V(5+)and "compressed" Ti4+ in Ca3Mg2TiV2O12, resulting in a negative deviation of 7.16% for Ca3Mg2SiV2O12 and a positive value of 5.66% for Ca3Mg2TiV2O12 between the porosity corrected er(Corr) (10.11 and 11.95) and theoretical eth (10.89 and 11.31) calculated by the C-M equation. The overall "rattling" effect in Ca3Mg2TiV2O12 results in a higher er and a nearer to zero tf compared to Ca3Mg2SiV2O12. Besides, the Q x f values of Ca3Mg2CV2O12 (C = Si, Ti) ceramics were correlated with relative density and Raman mode (A1g).

• 单位
  桂林理工大学; 广西大学