Effects of Ionic Coordination Bonding on Microwave Dielectric Properties of Y2CaBGa4O12 (B = Zr, Sn) Garnets

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

来源：ACS Applied Electronic Materials, 2022.

DOI：10.1021/acsaelm.2c00486

• Garnet structure
• Microwave dielectric properties
• Bond valence
• Ion coordination and bonding
• P-V-L theory

Two garnet-type electronic functional ceramics, Y2CaBGa4O12 (B = Zr, Sn), are reported, including their preparation process, microwave dielectric properties, and bonding properties. Acceptable microwave dielectric properties of epsilon(r) = 12.1 +/- 0.1, Q x f = 85,900 +/- 2000 GHz, and tau(f) = -45.5 +/- 1.5 ppm/degrees C for Y2CaZrGa4O12 and er = 10.6 +/- 0.1, Q x f = 95,750 +/- 2000 GHz, and tau(f) = -53.1 +/- 1.8 ppm/degrees C for Y2CaSnGa4O12 were achieved at 1450 degrees C. Compared with the ideal bond lengths, Ca-O, Zr-O, and Sn-O bonds are compressed, whereas the Y-O, Ga(1)-O, and Ga(2)-O bonds are in an expanded state. The positive weighted average difference factors (< d >) indicate that the ions of Y2CaZrGa4O12 (0.023 v.u.) and Y2CaSnGa4O12 (0.015 v.u.) are in an underbonded state on average, and the overall structures are in a slightly expanded state. The ionicity and energy of the bonds in Y2CaBGa4O12 ceramics were analyzed by the dielectric theory of chemical bonds. Compared to Y2CaSnGa4O12, the larger epsilon(r) in Y2CaZrGa4O12 comes down to the combined effect of the larger ionic polarizability of Zr4+ and a more substantial rattling effect, which also causes its tf to move toward the near-zero direction.

• 单位
  桂林理工大学; 广西大学