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A Novel Approach to the Sintering Schedule of Ba (Co0.7Zn0.3)1/3Nb2/3O3 Dielectric Ceramics for Microwave Applications

The present research is devoted to the optimization of the sintering schedule of Ba (Co0.7Zn0.3)1/3Nb2/3O3 (BCZN) dielectric ceramics for microwaves applications. A novel approach to the heat treatment of these ceramics based on the rapid-rate sintering (RRS) technique followed by a lower temperature annealing cycle has been developed. The relationships among the heat treatment process optimization, the structural, microstructural characteristics, and the microwave dielectric properties of the BCZN ceramics were investigated using X-ray diffraction, scanning electron microscopy, energy dispersion analysis, and vector network analysis. The RRS-technique shortens substantially the time required for the elaboration of these components in comparison with conventional sintering techniques and prevents simultaneously the formation of secondary phases as Ba5Nb4O15 and Ba8(Co, Zn) 1Nb6O24 on the surface of the ceramics. All of the sintered and annealed ceramics exhibit a high quality factor QF close to 110 000 GHz at 6 GHz. The high dielectric constant εr of ∼34.5 and a temperature coefficient of the resonant frequency τf of ∼0 ppm.C-1 were obtained in all annealed ceramics.