Ba $\mathsf{_{0.1}}$ Sr $\mathsf{_{0.9}}$ TiO $\mathsf{_{3}}$ -BaTi $\mathsf{_{4}}$ O $\mathsf{_{9}}$ composite thin films with improved microwave dielectric properties

Ba 0.1 Sr 0.9 TiO 3 -BaTi 4 O 9 composite thin films with different BaTi 4 O 9 concentrations were deposited on (100) LaAlO 3 (LAO) single crystal substrates via a pulsed laser deposition (PLD) using a combined target configuration of Ba 0.1 Sr 0.9 TiO 3 and BaTi 4 O 9 ceramics. The Ba 0.1 Sr 0.9 TiO 3 -BaTi 4 O 9 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 Ba 0.1 Sr 0.9 TiO 3 -BaTi 4 O 9 thin films changed from small ordered clusters to big triangle clusters with the increase of BaTi 4 O 9 concentration. The microwave dielectric properties of the Ba 0.1 Sr 0.9 TiO 3 -BaTi 4 O 9 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 Ba 0.1 Sr 0.9 TiO 3 -BaTi 4 O 9 thin films were modified by the addition of BaTi 4 O 9 . Specifically, the loss tangent of the composite thin films was greatly decreased from 0.025 for pure Ba 0.1 Sr 0.9 TiO 3 to 0.020 for the 4.7% BaTi 4 O 9 doped Ba 0.1 Sr 0.9 TiO 3 , and finally to 0.010 for the 15.9% BaTi 4 O 9 doped Ba 0.1 Sr 0.9 TiO 3 sample. Copyright Springer-Verlag Berlin/Heidelberg 2004