Preparation, characterization and microwave dielectric properties of A2BWO6 (A = Sr, Ba; B=Co, Ni, Zn) double perovskite ceramics

The A(2)BWO(6) (A = Sr, Ba; B = Co, Ni, Zn) microwave dielectric ceramics were prepared by conventional solid-state ceramic route. According to the X-ray diffraction (XRD) results, the ceramics have cubic perovskite structure for all compounds. In addition, the Ni-containing compounds showed apparent supperlattice reflections at low angles, whereas the others didn't. The results of Raman spectroscopy show that the degree of B-site ordering is different with different B2+ ions. The dielectric properties of the ceramics were measured in the frequency range 6.5 to 8.5 GHz using resonance methods. The ceramics have dielectric constant in the range 18 to 30, high quality factor (Q x f value up to 56000GHz) and negative temperature coefficient of resonant frequencies in the range -72.9 to -31.1ppm/degrees C. The dielectric constant increased with increasing B2+ ionic polarizability, and the quality factor was enhanced due to the increase in B-site ordering. The relationship between temperature coefficient of dielectric constant and tolerance factor was accordant in comparison with the other perovskites.