Microwave dielectric relaxation of the polycrystalline (Ba,Sr)TiO3 thin films

The microwave dielectric properties of the (Ba,Sr)TiO3 thin films annealed at various oxygen pressures ranging from 5to500mTorr were investigated over the frequency range 0.5–5GHz using a circular-patch capacitor geometry. The dielectric constant (ε) followed Curie–von Schweidler relaxation in the microwave-frequency range, and the degree of relaxation corresponded qualitatively with the measured dielectric loss (tanδ). As the oxygen pressure varied, the dielectric loss had a maximum value of ∼0.03 at 100mTorr, and its behavior was correlated with the Raman strength of the polar modes.