Relaxor-ferroelectric superlattices: High energy density capacitors

We report the breakdown electric field and energy density of laser ablated BaTiO 3/Ba (1x)Sr xTiO 3 (x=0.7) (BT/BST) relaxor-ferroelectric superlattices (SLs) grown on (100) MgO single crystal substrates. The dielectric constant shows a frequency dispersion below the dielectric maximum temperature (T m) with a merger above T m behaving similarly to relaxors. It also follows the basic criteria of relaxor ferroelectrics such as low dielectric loss over wide temperature and frequency, and 50K shift in T m with change in probe frequency; the loss peaks follow a similar trend to the dielectric constant except that they increase with increase in frequency (40kHz), and satisfy the nonlinear Vogel-Fulcher relation. Well-saturated ferroelectric hysteresis and 50-80% dielectric saturation are observed under high electric field (1.65MVcm 1). The superlattices demonstrate an in-built field in as grown samples at low probe frequency (<1kHz), whereas it becomes more symmetric and centered with increase in the probe frequency system (>1kHz) which rules out the effect of any space charge and interfacial polarization. The P-E loops show around 12.24Jcm 3 energy density within the experimental limit, but extrapolation of this data suggests that the potential energy density could reach 46Jcm 3. The current density versus applied electric field indicates an exceptionally high breakdown field (5.8-6.0MVcm 1) and low current density (10-25mAcm 2) near the breakdown voltage. The current-voltage characteristics reveal that the space charge limited conduction mechanism prevails at very high voltage. © 2012 IOP Publishing Ltd.