Dynamics of domain interfaces in a broad range of functional thin-film materials is an area of great current interest. In ferroelectric thin films, a significantly enhanced piezoelectric response should be observed if non-180 degrees domain walls were to switch under electric field excitation. However, in continuous thin films they are clamped by the substrate, and therefore their contribution to the piezoelectric response is limited. In this paper we show that when the ferroelectric layer is patterned into discrete islands using a focused ion beam, the clamping effect is significantly reduced, thereby facilitating the movement of ferroelastic walls. Piezo-response scanning force microscopy images of such islands in PbZr0.2Ti0.8O3 thin films clearly point out that the 90 degrees domain walls can move. Capacitors 1 microm2 show a doubling of the remanent polarization at voltages higher than approximately 15 V, associated with 90 degrees domain switching, coupled with a d33 piezoelectric coefficient of approximately 250 pm V-1 at remanence, which is approximately three times the predicted value of 87 pm V-1 for a single domain single crystal.

The magnesium-metal battery, which consists of a cathode, a Mg-metal anode, and a nonaqueous electrolyte, is a safer and less expensive alternative to the popular Li-ion battery. However, the performance of Mg batteries is greatly limited by the low electrochemical oxidative stability of nonaqueous electrolytes, the slow Mg 2+ diffusion into the cathode, and the irreversibility of Mg striping and plating on the Mg metal anode. Here, we report the first Mg-ion battery using a Mg 2+ aqueous electrolyte, nickel hexacyanoferrate cathode, and polyimide anode. The operation depends on Mg 2+ intercalation−deintercalation at the cathode and reversible enolization at the anode, accompanied by Mg 2+ transport between cathode and anode. The cell exhibits a maximum cell voltage of 1.5 V and a supercapacitor-like high power, and it can be cycled 5000 times. This system points the way to improved Mg-based rechargeable batteries.

We report on the out-of-plane piezoelectric response (d33), measured via piezoresponse scanning force microscopy, of submicron capacitors fabricated from epitaxial PbZrxTi1−xO3 thin films. Investigations on 1 μm2 and smaller capacitors show that the substrate-induced constraint is dramatically reduced by nanostructuring. At zero field, the experimentally measured values of d33 for clamped as well as submicron capacitors are in good agreement with the predictions from thermodynamic theory. The theory also describes very well the field dependence of the piezoresponse of clamped capacitors of key compositions on the tetragonal side of the PbZrxTi1−xO3 phase diagram as well as the behavior of submicron PbZr0.2Ti0.8O3 (hard ferroelectric) capacitors. However, the field-dependent piezoresponse of submicron capacitors in compositions closer to the morphotropic phase boundary (soft ferroelectrics) is different from the behavior predicted by the theoretical calculations.