Raman and dielectric study of Ba0.4Sr0.6TiO3–MgAl2O4 tunable microwave composite

( 1 − x ) Ba 0.4 Sr 0.6 TiO 3 – x MgAl 2 O 4 (x=0.00, 0.05, 0.10, 0.20, and 0.30) composite ceramics have been synthesized by the solid-state reaction, and its structural and dielectric properties have been systematically characterized. Two crystalline phases, a cubic perovskite structure Ba0.4Sr0.6TiO3 (BST) and a face-centered-cubic spinel structure MgAl2O4 (MA), are clearly visible for x≥0.05. As the MA content increases, the composite ceramics show an increased degree of deviation from the Curie–Weiss law and an increased diffuseness of the dielectric peak. Meanwhile, the tunability of composite ceramics increases. Raman analysis clearly indicates that the incorporation of MA lowers the permittivity and degrades the quality factor of BST composites, which is ascribed to the deterioration on B-site ordering of ABO3 perovskite structure.