Microwave dielectric property–microstructure relationships in Y2Ba(Cu1−xMg x)O5 solid solutions

Y2Ba(Cu1−xMgx)O5 solid solutions were synthesized by the solid state reaction method and the microstructure was studied by using SEM in order to clarify the microwave dielectric property–structure relationship. From the variations in the lattice parameters obtained by Rietveld analysis and the least-squares method, it was clarified that the limit of Y2Ba(Cu1−xMgx)O5 solid solutions is approximately at x=0.2. Grain growth and the reduction of porosity in the samples increased with the composition x. The dielectric constants were constant and the quality factors were extremely increased from 3800 to 42 300 GHz, as the composition x increased from 0 to 0.2. Thus, it was found that the quality factors of the samples were closely related to the morphological changes and a formation of the porosity; the temperature coefficient of resonant frequency of the samples ranged from −35.0 to −56.5 ppm/°C. Moreover, compared to Y2Ba(Cu1−xMgx)O5 compound without cold isotropic pressure (CIP), that with CIP especially exhibited approximately 16% higher Q·f value.