High dielectric tunability of Ba_(0.7)Sr_(0.3)TiO_3 thin films by compositional fluctuation of Ba/Sr ratio in micro-region

摘要

The perovskite Ba_(0.7)Sr_(0.3)TiO_3 thin films were fabricated by a sol-gel method with two kinds of microstructures, which are characterized were by fluctuant and homogeneous distribution of Ba/Sr ratio in micro-region respectively. It is found that the films with compositional inhomogeneity have higher dielectric tunability than that of the films with compositional homogeneity, 32% and 13% respectively at the bias field of 100kv/cm. From the TEM observation, we found the microdomain clusters with domain-width of 2-5nm. We proposed that the compositional heterogeneity of Ba and Sr in "A" sites of (Ba_(1-x)Sr_x)TiO_3 induces the lattice-metastability and promotes the sensitivity of phase transition to electric field, which gives rise to higher dielectric tunability.