Ba0.1Sr0.9TiO3-BaTi4O9 composite thin films with improved microwave dielectric properties

Ba0.1Sr0.9TiO3-BaTi4O9 composite thin films with different BaTi4O9 concentrations were deposited on (100) LaAlO3 (LAO) single crystal substrates via a pulsed laser deposition (PLD) using a combined target configuration of Ba0.1Sr0.9TiO3 and BaTi4O9 ceramics. The Ba0.1Sr0.9TiO3-BaTi4O9 thin films showed good crystal growth with c-orientation on (100) LAO substrates, which were characterized by X-ray diffraction (XRD). From scanning electron microscopy (SEM) measurements, we could see that the crystal grains of the Ba0.1Sr0.9TiO3-BaTi4O9 thin films changed from small ordered clusters to big triangle clusters with the increase of BaTi4O9 concentration. The microwave dielectric properties of the Ba0.1Sr0.9TiO3-BaTi4O9 thin films under low temperature range from 65 to 120 K were measured at 7.7 Ghz and the results showed that all the thin films were in the paraelectric state. The dielectric constant and loss tangent of the Ba0.1Sr0.9TiO3-BaTi4O9 thin films were modified by the addition of BaTi4O9. Specifically, the loss tangent of the composite thin films was greatly decreased from 0.025 for pure Ba0.1Sr0.9TiO3 to 0.020 for the 4.7% BaTi4O9 doped Ba0.1Sr0.9TiO3, and finally to 0.010 for the 15.9% BaTi4O9 doped Ba0.1Sr0.9TiO3 sample.