Chemical bond characteristics, Raman spectra, and microwave dielectric properties of garnet ceramics Ca3B2ZnGa2O12 (B = Nb, Sb)

作者：Zhang, Ning; Tang, Ying^*; Xiang, Huaicheng^*; Fang, Liang

来源：Ceramics International, 2023, 49(13): 22273-22280.

DOI：10.1016/j.ceramint.2023.04.057

• Microwave dielectric properties
• Garnet
• Bond valence
• Ionic polarizability
• P-V-L theory

Two cubic garnet ceramics, Ca3B2ZnGa2O12 (B = Nb, Sb), were synthesized via the solid-state approach, where Zn2+ and Ga3+ jointly occupied the tetrahedra (C-site), and Nb5+ (or Sb5+) fully occupied the octahedra (B-site). Ca3Nb2ZnGa2O12 ceramic sintered at 1390 degrees C possessed a relatively larger & epsilon;r, & tau;f, and Q x f value of 16.57,-44.0 ppm/degrees C, and 39,200 GHz compared to & epsilon;r = 9.04, Q x f = 25,300 GHz, and & tau;f =-61.2 ppm/degrees C for Ca3Sb2Zn-Ga2O12 fired at 1270 degrees C. Bond valence, ionic polarizability, packing fraction, Raman spectroscopy, and the P-V-L chemical bond theory were used to investigate the intrinsic factors affecting microwave dielectric properties. Compared with the measured permittivity & epsilon;r, the theoretical permittivity & epsilon;r(C-M) of Ca3Nb2ZnGa2O12 is under-estimated, and Ca3Sb2ZnGa2O12 shows the opposite trend, which is mainly related to the under-and over -bonding in the structure. The packing fraction of Ca3Nb2ZnGa2O12 is slightly lower than that of Ca3Sb2Zn-Ga2O12, but it does not lead to the low Q x f value of Ca3Nb2ZnGa2O12. The variation in Q x f was related to relative density, weak short-range order (SRO), and lattice energy. The minus sign and magnitude of & tau;f for both ceramics were determined by their large positive & tau;& alpha;m values.

• 单位
  广西大学; y; 桂林理工大学