Microstructure and dielectric properties of compositionally graded Ba1-xSrxTiO3 multilayer tunable capacitors

Abstract

Li2O/B2O3-added Ba1-xSrxTiO3 (B1-xSxT) ceramics, where 0.2 <= x <= 0.35, were well densified at 920 degrees C with pure perovskite structure. The dielectric constant, tunability, and figure of merit (FOM) of B1-xSxT ceramics increased with x because of the decreasing Curie temperature (T-C). The specimen with x = 0.35, whose T-C was close to room temperature, exhibited a large tunability of 27.4 % and FOM of 110 at 10 kV/cm. A compositionally graded multilayer (CGML), which was sintered at 920 degrees C, was fabricated using B1-xSxT thick films to produce a temperature-stable tunable capacitor, and it evinced a dense microstructure and a continuous interface between the B1-xSxT thick film and the Ag electrode. This CGML capacitor showed a large tunability (51 %) and FOM (150) at 20 kV/cm. It also exhibited stable tunability (17-28 % at 10 kV/cm) at temperatures between 30-90 degrees C. Therefore, the B1-xSxT CGML capacitor is a suitable candidate for temperature-stable tunable capacitors.