High-temperature relaxation and microwave dielectric response of (1-x)BaNd1.76Bi0.24Ti5O14-xBa0.6Sr0.4La4Ti4O15 compounds with adjustable medium-high dielectric constant

Dielectric ceramics in the microwave band are one of the crucial materials for mobile communication technology, and the studying of their phase evolution and defect behavior can help to understand and reduce dielectric loss. In this work, (1-x)BaNd1.76Bi0.24Ti5O14-xBa0.6Sr0.4La4Ti4O15 (x = 0.2, 0.4, 0.6 and 0.8, (1-x)BNT-xBSLT) ceramics were synthesized by solid-state reaction method. X-ray diffraction (XRD) and Raman spectra analysis reveal that tungsten bronze and hexagonal perovskite phases coexist in the ceramics, and BaNd2Ti3O10 is indexed as the main crystalline phase at x = 0.4, 0.6, leading to a deterioration of the microwave dielectric properties. The defect-related relaxation behavior and its effect on microwave dielectric properties were analyzed by dielectric temperature spectrum and thermally stimulated depolarization current (TSDC). The relationship between the dielectric constant and the electric field distribution was solved using the eigenmode of the high frequency structure simulator. In short, the (1-x)BNT-xBSLT ceramics at x = 0.8 exhibit excellent microwave dielectric properties: epsilon r = 47.2, Qxf = 16,800 GHz, and tau f = -4.6 ppm/degrees C. The microwave dielectric response of BNT-BSLT composite ceramics is closely related to the phase composition and defects, which is informative for the development of low dielectric loss ceramics.