Structure, Raman spectra and microwave dielectric properties of novel garnet-type Ca3MZrGe3O12 (M = Co, Zn) ceramics

Abstract

Two novel garnet-type ceramics Ca3MZrGe3O12 (M = Co and Zn) with pure phase were prepared through a solid-state reaction method. Structure–property relationships were studied by the Rietveld refinement and Raman spectra. The appearance of two weak symmetric stretching vibrational peaks in Ca3ZnZrGe3O12 might be due to the lower ordering. Higher Q × f value in Co-analogue was related to the larger packing fraction and the lower FWHM of A1g mode. The smaller oxygen bond valence in Ca3CoZrGe3O12 indicates a smaller τf value. At the optimized sintering temperature of 1280 °C, Ca3CoZrGe3O12 shows desirable microwave dielectric properties with εr of 10.37, Q × f value of 60,100 GHz, and τf value of −28.5 ppm/oC. The Ca3ZnZrGe3O12 ceramic sintered at 1200 °C has the best microwave dielectric properties with εr of 10.48, Q × f value of 49,700 GHz, and τf value of −35.8 ppm/oC.

Keywords

• garnets
• low permittivity
• microwave dielectric properties
• raman spectroscopy