Giant low frequency dielectric tunability in high-k Ba (Fe1/2 Nb1/2)O3 ceramics at room temperature

The effect of electric field on the dielectric properties of high-k Ba (Fe1/2Nb1/2) O3ceramics with different grain sizes is reported. A low frequency giant dielectric tunability (>85%) can be obtained under a bias field as low as 50 V/mm. The results suggest that the giant dielectric tunability originates from extrinsic contributions such as domain boundary and oxygen defect relaxations. These findings provide a clear understanding to the complicated dielectric response in a family of high- k ceramics and a key to the high tunability of nonferroelectrics under low electric fields, which is attractive for potential applications in tunable devices.