Jonathan E Spanier

This data package contains the data used in the derivation of the strain-temperature phase diagrams of epitaxial barium strontium titanate solid solutions. The data contains the description of the phase boundaries across multiple chemical compositions of the solid solution. The package also includes the ferroelectric equilibrium states (polarization, domain wall orientation, domain volume fractions) as a function of the biaxial epitaxial misfit strain, temperature, chemical composition of the solid solution. The equilibrium states are provided for the single-domain and polydomain/heterophase configurations of the material. The equilibrium states are used in the definition of the phase diagrams and the corresponding phase boundaries included in the dataset.

Realization of tunable materials that are multifunctional and maintain high performance in dynamically changing environments is a fundamental goal of science and engineering. Tunable dielectrics form the basis of a wide variety of communication and sensing devices and require breakthrough performance improvement to enable next-generation technologies. Using phenomenological modeling, film growth, and characterization, we show that devices consisting of domain-wall-rich BaSrTiOfilms close to a polar-domain-variant phase boundary exhibit colossal dielectric tunability of 100:1 (99%) at a voltage (electric field) of ~15 V (750 kV/cm), resulting in a tunability-quality factor product figure of merit that rises to nearly 10, two orders of magnitude higher than the best previous reported values. Remarkably, varying the amplitude of alternating-current bias enables modulation of this tunability by 50%, owing to domain-wall motion. These results suggest that domain engineering is a powerful approach for achieving excellent modulation of functional properties in ferroelectric films.

Nanodielectrics based upon nanoscale Ba(Ti, M V )O 3 , where M = Nb or Ta, were prepared and electrically characterized for their potential use as a high permittivity dielectric layer. Nanocrystals of Ba(Ti, Nb)O 3 (BTNO) and Ba(Ti, Ta)O 3 (BTTO) of average size 20 nm (range 10-50 nm) with a non-centrosymmetric (polarizable) crystal structure were synthesized, dispersed in alcohol solvents and blended with three polymers of known but differing dielectric and electromechanical behavior: Polyvinylpyrrolidone (PVP), Polyfurfuryl alcohol (PFA) and Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE). 0-3 nanoparticle-polymer pressed pellets, films and metal-insulator-metal devices were prepared for electrical characterization. Analysis of the Ba(Ti, M V )O 3 -PVP and Ba(Ti, M V )O 3 -PFA composites showed a high effective permittivity, low loss, low leakage and voltage tolerance, demonstrating the capability for high energy density capacitance. Effective permittivity, of 52 (BTNO-PFA) and 42 (BTTO-PFA) for pellet nanocomposites and 32 (BTNO-PVP) and 20 (BTNO-PVP) film nanocomposites were observed at 1 MHz respectively. Voltage breakdown strengths of 2133 V/mm (BTNO) and 833 V/mm (BTTO) were demonstrated respectively (threshold 0.1 μA). Linear and non-linear dielectric behavior was studied by polarization-electric field (P-E) hysteresis measurements. Nanocomposites of BTNO-PVDF-TrFE were prepared to assess the viability of making ferroelectric nanocomposites over a range of polymer-nanoparticle volume fractions.

Enhanced susceptibilities in ferroelectrics often arise near phase boundaries between competing ground states. While chemically-induced phase boundaries have enabled ultrahigh electrical and electromechanical responses in lead-based ferroelectrics, precise chemical tuning in lead-free alternatives, such as (K,Na)NbO
3
thin films, remains challenging due to the high volatility of alkali metals. Here, we demonstrate strain-induced morphotropic phase boundary-like polymorphic nanodomain structures in chemically simple, lead-free, epitaxial NaNbO
3
thin films. Combining ab initio simulations, thin-film epitaxy, scanning probe microscopy, synchrotron X-ray diffraction, and electron ptychography, we reveal a labyrinthine structure comprising coexisting monoclinic and bridging triclinic phases near a strain-induced phase boundary. The coexistence of energetically competing phases facilitates field-driven polarization rotation and phase transitions, giving rise to a multi-state polarization switching pathway and large enhancements in dielectric susceptibility and tunability across a broad frequency range. Our results open new possibilities for engineering lead-free thin films with enhanced functionalities for next-generation applications.
The authors demonstrate strain-induced morphotropic phase boundary-like nanodomains in lead-free NaNbO
3
thin films, enabling multi-state switching and large enhancements in dielectric susceptibility and tunability over a broad frequency range.

MXenes represent one‐of‐a‐kind materials to devise radically novel technologies and achieve breakthroughs in optoelectronics. To exploit their full potential, precise control over the influence of stoichiometry on optical and thermal properties, as well as device performance, must be achieved. Here, the characteristics of optoelectronic devices based on Ti 3 C 2 T x and Ti 2 CT x thin films are uncovered, highlighting the striking difference in their photothermal responses to laser irradiation under different experimental conditions. Even though their absorption coefficients at 450 nm are comparable, the thermal excitation and relaxation phenomena display markedly different kinetics: Ti 2 CT x devices show a strong asymmetry during the heating‐cooling cycle, with the heat dissipation kinetics being three orders of magnitude slower than Ti 3 C 2 T x and strongly influenced by environmental conditions. The findings are expected to stimulate fundamental investigations into the photothermal response of MXenes and open exciting prospects for their use in printed and wearable optoelectronics, including memory devices and neuromorphic computing.

Highly responsive, voltage-tunable dielectrics are essential for microwave-telecommunication electronics. Ferroelectric/relaxor materials have been leading candidates for such functionality and have exhibited agile dielectric responses. Here, it is demonstrated that relaxor materials developed from antiferroelectrics can achieve both ultrahigh dielectric response and tunability. The system, based on alloying the archetypal antiferroelectric PbZrO3 with the dielectric BaZrO3, exhibits a more complex phase evolution than that in traditional relaxors and is characterized by an unconventional multi-phase competition between antiferroelectric, ferroelectric, and paraelectric order. This interplay of phases can greatly enhance the local heterogeneities and results in relaxor characteristics while preserving considerable polarizability. Upon studying Pb1-xBaxZrO3 for x = 0-0.45, Pb0.65Ba0.35ZrO3 is found to provide for exceptional dielectric tunability under low bias fields (approximate to 81% at 200 kV cm(-1) and approximate to 91% at 500 kV cm(-1)) at 10 kHz, outcompeting most traditional relaxor ferroelectric films. This high tunability is sustained in the radio-frequency range, resulting in a high commutation quality factor (>2000 at 1 GHz). This work highlights the phase evolution from antiferroelectrics (with lower, "positive" dielectric tunability) to relaxors (with higher, "negative" tunability), underscoring a promising approach to develop relaxors with enhanced functional capabilities and new possibilities.

This dataset contains raw and processed experimental data supporting the
study “Strain-induced lead-free morphotropic phase boundary.” Data were
collected from NaNbO₃ thin films of varying thicknesses using techniques
such as reciprocal space mapping (RSM), high-resolution X-ray diffraction
(HRXRD), atomic force microscopy (AFM), piezoresponse force microscopy
(PFM), scanning transmission electron microscopy (STEM), X-ray
photoelectron spectroscopy (XPS), dielectric spectroscopy, and
ferroelectric measurements. Files are organized by sample ID, with
filenames indicating technique, sample thickness, date, and format. Data
formats include .csv for tabular values, .ibw for Igor Pro binary
waveforms, .pvsm and .vti for ParaView visualization states, .xrdml for
XRD raw data, and image formats (.png, .PNG). These files can be reused to
replicate the analyses presented in the associated article, enable
independent phase and domain structure studies, and support the
development of phase boundary engineering strategies in lead-free
ferroelectric thin films. The dataset is released under the Creative
Commons Zero (CC0) license and contains no personal or sensitive
information.

Ferroelectric nitrides attract immense attention due to their excellent electrical, mechanical, and thermal properties as well as for their compatibility with scalable semiconductor technology. The availability of high‐quality nitride films possessing tailorable coercive voltage and field, however, remains challenging, and is a key for deeper exploration of switching dynamics and practical applications in low‐power devices. 2D growth of epitaxial thin (≲20 nm) c ‐axis‐oriented Sc 0.3 Al 0.7 N films is reported on Al 2 O 3 (0001) and on electrically conductive 4 H ‐SiC (0001), obtained by reflection high‐energy electron diffraction‐monitored layer‐by‐layer physical vapor deposition growth. Films exhibit high quality, as evidenced by rocking curve full‐width at half‐maximum (FWHM) as narrow as ≈0.02°, and an atomically abrupt film‐substrate interface with low dislocation density. The coercive field of Sc 0.3 Al 0.7 N/4 H ‐SiC (0001) heterostructures is as low as 2.75 MV cm −1 . Moreover, a high endurance of >10 9 cycles at saturation polarization is achieved. Density functional theory calculations of a model system reveal that an improved crystal quality, including atomically abrupt ferroelectric nitride‐metal interface, facilitates the reduction in the switching barriers, and leads to reduced coercivity. These findings demonstrate the feasibility of obtaining high‐quality epitaxial ferroelectric nitride films on highly scalable and radiation‐resistant substrates, and their potential for energy‐efficient electronic devices.

Switchable order parameters in ferroic materials are essential for
functional electronic devices, yet disruptions of the ordering can take
the form of planar boundaries or defects that exhibit distinct
properties from the bulk, such as electrical (polar) or magnetic
(spin) response. Characterizing the structure of these boundaries is
challenging due to their confined size and three-dimensional nature. Here,
a chemical anti-phase boundary in the highly ordered double perovskite
Pb2MgWO6 is investigated using multislice electron ptychography.
The boundary is revealed to be inclined along the electron beam direction
with a finite width of chemical intermixing. Additionally, regions at and
near the boundary exhibit antiferroelectric-like displacements,
contrasting with the predominantly paraelectric matrix. Spatial statistics
and density functional theory calculations further indicate that despite
their higher energy, chemical anti-phase boundaries form due to kinetic
constraints during growth, with extended antiferroelectric-like
distortions induced by the chemically frustrated environment in the
proximity of the boundary. The three-dimensional imaging provides critical
insights into the interplay between local chemistry and the polar
environment, elucidating the role of anti-phase boundaries and their
associated confined structural distortions and offering new opportunities
for engineering ferroic thin films.