High tunability and low loss via establishing an internal electric field in LiFe5O8/Ba0.6Sr0.4TiO3 composite films using chemical solution deposition method

It is hard to simultaneously realize the high dielectric tunability and low loss for the single Ba0.6Sr0.4TiO3 (BST) ferroelectric film or its composites with the linear dielectrics. In this work, LiFe5O8/Ba0.6Sr0.4TiO3 (LFO/BST) composite films were fabricated via chemical solution deposition method, where the internal electric field could be established inside the film owing to the lithium ions’ de-intercalating effect of LiFe5O8 (LFO) layer under the bias field. Thus, we successfully achieved a high dielectric tunability and low loss in the composite films. Owing to the coupling effect in composite films, the dielectric constant remained unchanged at high frequency, while the dielectric loss was reduced to 0.008. An excellent tunability of 71.30% under the bias electric field of −340 kV/cm was obtained in LFO/BST film, which was 41.58% higher than that of BST film. Additionally, the response characteristic of the dielectric constant to the bias field exhibited an asymmetric butterfly curve for LFO/BST composite films. The dielectric tunability in LFO/BST composite films was 19.30% and 71.30% at 1 MHz, under the DC bias field of +340 kV/cm and −340 kV/cm, respectively. These phenomena can be explained in terms of the internal electric field inside the film under the action of the bias field.