Influence of B-site rare-earth Yb cation on the crystal structure and microwave dielectric properties of Ca3Yb2Ge3O12 garnet ceramics

Abstract

In this work, garnet structured Ca3Yb2Ge3O12 ceramics with a space group of Ia-3d were synthesized by a solid-state reaction method. Rietveld refinement analysis demonstrated that Yb3+with small ionic radius and large electronegativity entered the B-sites and shortened the bond length of B–O and Ge–O. The bond valence and P-V-L theory analysis results showed that Ca cations with a weakened rattling effect exerted a critical effect on the dielectric constant, and the Ge–O bond was the main factor that influenced dielectric loss. Ca3Yb2Ge3O12 with a high relative density (98.2%) and excellent microwave dielectric properties (εr= 10.2, Q × f = 98,400 GHz, τf = -48 ppm/°C) was obtained at 1360 °C for 4 h. Furthermore, the intrinsic dielectric constant and dielectric loss (εr =10.12, Q × f = 101,900 GHz) of Ca3Yb2Ge3O12 were obtained by infrared reflectivity spectroscopy.