Low-loss Ca_(5-x)Sr_xA_2TiO_(12) [A=Nb,Ta] ceramics: Microwave dielectric properties and vibrational spectroscopic analysis

摘要

Complex perovskite-type Ca_(5-x)Sr_xA_2TiO_(12) [A=Nb,Ta] (0 ≤ x ≤ 5) ceramics were prepared by conventional solid-state ceramic route. The crystal structure, microwave dielectric properties, and vibrational spectroscopic characteristics of these materials are reported. The structure and microstructure were investigated by x-ray diffraction and scanning electron microscopy techniques. The microwave dielectric properties were measured in the 3-5-GHz frequency range by the resonance method. Structural evolutions from orthorhombic to an averaged pseudocubic phase, with associated changes in dielectric properties, were observed as a function of composition. The structure-property relationships in these ceramics were established using Raman and Fourier transform infrared spectroscopic techniques. Raman analysis showed characteristic bands of ordered perovskite materials, with variation in both intensity and frequency as a function of composition.