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The effect of an electric field on local domain structure near a 24° tilt grain boundary in a 200 nm-thick Pb(Zr_0.2Ti_0.8)O₃bi-crystal ferroelectric film was probed using synchrotron nanodiffraction. The bi-crystal film was grown epitaxially on SrRuO₃-coated (001) SrTiO₃24° tilt bi-crystal substrates. From the nanodiffraction data, real-space maps of the ferroelectric domain structure around the grain boundary prior to and during application of a 200 kV cm⁻¹electric field were reconstructed. In the vicinity of the tilt grain boundary, the distributions of densities ofc-type tetragonal domains with thecaxis aligned with the film normal were calculated on the basis of diffracted intensity ratios ofc- anda-type domains and reference powder diffraction data. Diffracted intensity was averaged along the grain boundary, and it was shown that the density ofc-type tetragonal domains dropped to ∼50% of that of the bulk of the film over a range ±150 nm from the grain boundary. This work complements previous results acquired by band excitation piezoresponse force microscopy, suggesting that reduced nonlinear piezoelectric response around grain boundaries may be related to the change in domain structure, as well as to the possibility of increased pinning of domain wall motion. The implications of the results and analysis in terms of understanding the role of grain boundaries in affecting the nonlinear piezoelectric and dielectric responses of ferroelectric materials are discussed. 

Antiferroelectric (Pb0.87Sr0.05Ba0.05La0.02)(Zr0.52Sn0.40Ti0.08)O3 thin film capacitors were fabricated for dielectric energy storage. Thin films with excellent crystal quality (FWHM 0.021°) were prepared on (100) SrRuO3/SrTiO3 substrates by pulsed laser deposition. The out-of-plane lattice constant of the thin film was 4.110 ± 0.001 Å. An average maximum recoverable energy storage density, 88 ± 17 J cm−3 with an efficiency of 85% ± 6% at 1 kHz and 80 ± 15 J cm−3 with an efficiency of 91% ± 4% at 10 kHz, was achieved at room temperature. The capacitor was fatigue resistant up to 106 cycles at an applied electric field of 2 MV cm−1. These properties are linked to a low level of hysteresis and slow polarization saturation. PbZrO3-derived oxide thin film capacitors are promising for high efficiency and low loss dielectric energy storage applications. 

The rapid development of computation power and machine learning algorithms has paved the way for automating scientific discovery with a scanning probe microscope (SPM). The key elements toward operationalization of the automated SPM are the interface to enable SPM control from Python codes, availability of high computing power, and development of workflows for scientific discovery. Here, we build a Python interface library that enables controlling an SPM from either a local computer or a remote high-performance computer, which satisfies the high computation power need of machine learning algorithms in autonomous workflows. We further introduce a general platform to abstract the operations of SPM in scientific discovery into fixed-policy or reward-driven workflows. Our work provides a full infrastructure to build automated SPM workflows for both routine operations and autonomous scientific discovery with machine learning. 

In many commercially utilized ferroelectric materials, the motion of domain walls is an important contributor to the functional dielectric and piezoelectric responses. This paper compares the temperature dependence of domain wall motion for BaTiO3 ceramics with different grain sizes, point defect concentrations, and formulations. The grain boundaries act as significant pinning points for domain wall motion such that fine-grained materials show smaller extrinsic contributions to the properties below the Curie temperature and lower residual ferroelectric contributions immediately above the Curie temperature. Oxygen vacancy point defects make a modest change in the extrinsic contributions of undoped BaTiO3 ceramics. In formulated BaTiO3, extrinsic contributions to the dielectric response were suppressed over a wide temperature range. It is believed this is due to a combination of reduced grain size, the existence of a core-shell microstructure, and a reduction in domain wall continuity over the grain boundaries. 

In undoped lead zirconate titanate films of 1–2  μm thick, domain walls move in clusters with a correlation length of approximately 0.5–2  μm. Band excitation piezoresponse force microscopy mapping of the piezoelectric nonlinearity revealed that niobium (Nb) doping increases the average concentration or mobility of domain walls without changing the cluster area of correlated domain wall motion. In contrast, manganese (Mn) doping reduces the contribution of mobile domain walls to the dielectric and piezoelectric responses without changing the cluster area for correlated motion. In both Nb and Mn doped films, the cluster area increases and the cluster density drops as the film thickness increases from 250 to 1250 nm. This is evident in spatial maps generated from the analysis of irreversible to reversible ratios of the Rayleigh coefficients. 

Piezoelectric microelectromechanical systems (piezoMEMS) enable dense arrays of actuators which are often driven to higher electrical fields than their bulk piezoelectric counterparts. In bulk ceramics, high field driving causes internal heating of the piezoelectric, largely due to field-induced domain wall motion. Self-heating is then tracked as a function of vibration velocity to determine the upper bound for the drive levels. However, the literature is limited concerning self-heating in thin film piezoMEMS. In this work, it is shown that self-heating in piezoMEMS transducer arrays occurs due to domain wall motion and Ohmic losses. This was demonstrated via a systematic study of drive waveform dependence of self-heating in piezoMEMS arrays. In particular, the magnitude of self-heating was quantified as a function of different waveform parameters (e.g., amplitude, DC offset, and frequency). Thermal modeling of the self-heating of piezoMEMS using the measured hysteresis loss from electrical characterization as the heat source was found to be in excellent agreement with the experimental data. The self-heating model allows improved thermal design of piezoMEMS and can, furthermore, be utilized for functional heating, especially for device level poling. 

When utilizing double-beam laser interferometry to assess the piezoelectric coefficient of a film on a substrate, probing both top and bottom sample surfaces is expected to correct the erroneous bending contribution by canceling the additional path length from the sample height change. However, when the bending deformation becomes extensive and uncontrolled, as in the case of membranes or fully released piezoelectric films, the double-beam setup can no longer account for the artifacts, thus resulting in inflated film displacement data and implausibly large piezoelectric coefficient values. This work serves to identify these challenges by demonstrating d33,f measurements of fully released PZT films using a commercial double-beam laser interferometer. For a 1 μm thick randomly oriented PZT film on a 10 μm thick polyimide substrate, a large apparent d33,f of 9500 pm/V was measured. The source of error was presumably a distorted interference pattern due to the erroneous phase shift of the measurement laser beam caused by extensive deformation of the released sample structure. This effect has unfortunately been mistaken as enhanced piezoelectric responses by some reports in the literature. Finite element models demonstrate that bending, laser beam alignment, and the offset between the support structure and the electrode under test have a strong influence on the apparent film d33,f.