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Abstract Improvements in the polarization of environmentally-friendly perovskite ferroelectrics have proved to be a challenging task in order to replace the toxic Pb-based counterparts. In contrast to common methods by complex chemical composition designs, we have formed Mn-inlaid antiphase boundaries in Mn-doped (K,Na)NbO3 thin films using pulsed laser deposition method. Here, we observed that mono- or bi-atomic layer of Mn has been identified to inlay along the antiphase boundaries to balance the charges originated from the deficiency of alkali ions and to induce the strain in the KNN films. Thus, rectangular saturated polarization-electric field hysteresis loops have been achieved, with a significantly improved twice remanent polarization of 114 μC/cm2 with an applied electric field of 606 kV/cm, which can be comparable to that of the typical Pb-based thin films. Moreover, we directly see the Mn occupation at the A-site of KNN perovskite structure using atomic-scale microstructure and composition analysis. The Mn-inlaid antiphase boundary can further enrich the understanding of perovskite crystal structure and give more possibilities for the design and optimization of perovskite materials.

Abstract In situ high-pressure/high-temperature Raman-scattering analyses on PbTiO $$_3$$ 3 , 0.92PbTiO $$_3-$$ 3 - 0.08Bi(Zn $$_{0.5}$$ 0.5 Ti $$_{0.5}$$ 0.5 )O $$_3$$ 3 and 0.83PbTiO $$_3-$$ 3 - 0.17Bi(Mg $$_{0.5}$$ 0.5 Ti $$_{0.5}$$ 0.5 )O $$_3$$ 3 single crystals reveal an intensity transfer between the fine-structure components of the A $$_1$$ 1 (TO) soft mode. The enhancement of the lowest-energy subpeak, which stems from intrinsic local non-tetragonal polar distortions, along with the suppression of the tetragonal A $$_1$$ 1 (1TO) fundamental mode with increasing pressure and temperature indicates the key role of the local polarization fluctuations in transformation processes and emphasizes the significance of the order-disorder phenomena in both the pressure- and temperature-induced phase transitions of pure PbTiO $$_3$$ 3 and its solid solutions with complex perovskites. Moreover, the temperature and pressure evolution of the fraction of the local non-tetragonal polar distortions is highly sensitive to the type of B-site substituent.

X-ray photon correlation spectroscopy (XPCS) holds strong promise for observing atomic-scale dynamics in materials, both at equilibrium and during non-equilibrium transitions. Here an in situ XPCS study of the relaxor ferroelectric PbMg1/3Nb2/3O3 (PMN) is reported. A weak applied AC electric field generates strong response in the speckle of the diffuse scattering from the polar nanodomains, which is captured using the two-time correlation function. Correlated motions of the Bragg peak are also observed, which indicate dynamic tilting of the illuminated volume. This tilting quantitatively accounts for the observed two-time speckle correlations. The magnitude of the tilting would not be expected solely from the modest applied field, since PMN is an electrostrictive material with no linear strain response to the field. A model is developed based on non-uniform static charging of the illuminated surface spot by the incident micrometre-scale X-ray beam and the electrostrictive material response to the combination of static and dynamic fields. The model qualitatively explains the direction and magnitude of the observed tilting, and predicts that X-ray-induced piezoresponse could be an important factor in correctly interpreting results from XPCS and nanodiffraction studies of other insulating materials under applied AC field or varying X-ray illumination.

Lead-free bismuth sodium titanate (Bi0.5Na0.5)TiO3 (BNT) and related solid solutions are potential piezoelectric materials for such applications as actuators and transducers if their excellent strain responses and piezoelectric properties can be optimized. In this work, a large strain response of 0.61% is achieved in lead-free (0.94-x%)(Bi0.5Na0.5)TiO3-0.06BaTiO3-x%NaNbO3 (x = 0 –6, BNT-6BT-xNN) ceramics with the composition of x = 3.5 in a pseudo-cubic structure. Coexistence of ferroelectric (FE) and relaxor (RE) domain structures is observed in all the unpoled ceramics and the enhanced strain response is believed to be related to the evolution of the ergodic relaxor (ER) and non-ergodic (NR) states thanks to the substitution of antiferroelectric NN. BNT-6BT-3.5NN is a critical composition near the FE/NR/ER phase boundary close to room temperature (RT) and its high strain response arises from a synergistic combination of a reversible electric-field-induced phase transition and an active domain switching in the mixed NR/ER state. This work provides new insights into the dynamic interplay between mesoscopic domains and macroscopic electrical properties in the BNT-based piezoceramics.

The integration of epitaxial complex oxides on semiconductor and flexible substrates is required but challenging. Here, the authors report the highly heterogeneous epitaxy of transferrable BaTiO3-δ membrane with enhanced flexoelectricity on Ge (011).

Hardware electronic synapse and neuro-inspired computing system based on phase change random access memory (PCRAM) have attracted an extensive investigation. However, due to the intrinsic asymmetric reversible phase transition, the defective weight update of PCRAM synapses in aspects of tuning range, linearity and continuity has long required a system-level complexity of circuits and algorithms. The cell-level improvements to a great extent may slim the system thus achieving efficient computing. We report in this work the great enhancement of Ge2Sb2Te5 (GST) based PCRAM synapses by combining materials engineering and pulse programming. It is found that carbon doping in GST retards the rate of phase changing thus increasing the controllability of the conductance, while non-linear programmable pulse excitations can eventually lead to a reliable synaptic potentiation and depression. A set of improved programmable pulse schemes for spike-timing dependent plasticity was then demonstrated, suggesting its potential superiority in flexible programming and reliable data collection. Our methods and results are of great significance for implementing PCRAM electronic synapses and high-performance neuro-inspired computing.

Relaxor ferroelectrics are a type of material exhibiting electrostriction whereby a change in the material shape occurs under an applied electric field; however, although known by the community for many years the underlying mechanisms of the phenomenon and the characteristic relaxations still remain under debate. To help address this issue, the authors report an equivalent circuit analysis revealing the key role of a constant phase element in the behaviour of relaxor ferroelectric single crystals.

Phase transition brings a plethora of exotic phenomena and intriguing effects such as spin and charge frustration. However, the phase transition order is not always explicit. Here, the authors discover phase transition frustration near a tricritical composition point in ferroelectric Pb(Zr,Ti)O3.

Lead hafnate (PbHfO3) has attracted a lot of renewed interest due to its potential as antiferroelectric (AFE) material for energy storage. However, its room temperature (RT) energy-storage performance has not been well established and no reports on the energy-storage feature of its high-temperature intermediate phase (IM) are available. In this work, high-quality PbHfO3 ceramics were prepared via the solid-state synthesis route. Based on high-temperature X-ray diffraction data, the IM of PbHfO3 was found to be orthorhombic, Imma space group, with antiparallel alignment of Pb2+ ions along the [001]cubic directions. The polarization–electric field (P–E) relation of PbHfO3 is displayed at RT as well as in the temperature range of the IM. A typical AFE loop revealed an optimal recoverable energy-storage density (Wrec) of 2.7 J/cm3, which is 286% higher than the reported data with an efficiency (η) of 65% at 235 kV/cm at RT. A relatively high Wrec value of 0.7 J/cm3 was found at 190 °C with an η of 89% at 65 kV/cm. These results demonstrate that PbHfO3 is a prototypical AFE from RT up to 200 °C, making it a suitable material for energy-storage applications in a wide temperature range.

The HfO2-based resistive random access memory (RRAM) is one of the most promising candidates for non-volatile memory applications. The detection and examination of the dynamic behavior of oxygen ions/vacancies are crucial to deeply understand the microscopic physical nature of the resistive switching (RS) behavior. By using synchrotron radiation based, non-destructive and bulk-sensitive hard X-ray photoelectron spectroscopy (HAXPES), we demonstrate an operando diagnostic detection of the oxygen ‘breathing’ behavior at the oxide/metal interface, namely, oxygen migration between HfO2 and TiN during different RS periods. The results highlight the significance of oxide/metal interfaces in RRAM, even in filament-type devices.

Pure-phase Pb(Cd1/3Nb2/3)O3 (PCN) single crystals and ceramics with a complex perovskite structure are synthesized for the first time. The local chemical ordering in PCN has been investigated by X-ray diffraction (including diffuse scattering) and Cs-corrected transmission electron microscopy experiments. It is concluded that the PCN samples have large coherent chemical ordering regions that even extend to the long range, and the ordering model is consistent with β-type chemical ordered regions. The antiphase domain boundaries were also observed. Two dielectric anomaly peaks were found in these two types of samples, one of which indicates possible relaxor behaviour. The novel structure of the completely ordered regions and its relationship with the electrical properties make PCN a unique material for the fundamental understanding of chemically substituted perovskites.

PbZrO3-based antiferroelectric crystals are of great interest in both fundamental and applied research, not only because of the antiferroelectric feature at room temperature but also because of the existence of a peculiar intermediate state at elevated temperatures. Here, we report a detailed description of domain structure change at the temperature-induced antiferroelectric-to-ferroelectric phase transition. A complex process of different types of domains is revealed to appear at different stages of the phase transition. A hierarchical ferroelastic domain structure forms in the stabilized intermediate state, where the dense domain walls show potential impact on the physical properties of the crystal.

This editorial celebrates the 10th anniversary of Journal of Advanced Dielectrics (JAD) which was launched in January 2011.

Lead zirconate titanate (PZT) is one of the most widely studied piezoelectric materials, mainly because of its `mysterious' relationship between the so-called morphotropic phase boundary (MPB) and its strong piezoelectric coupling factor. Using results from a pair distribution function analysis, this paper examines how the complex local structure in PZT affects the long-range average structure across the MPB. A monoclinic MC type structure is discovered in PZT. A first-order transformation between the monoclinic MA and MC components in both the average and local structures explains the sudden change in piezoelectric effect around these compositions. The role of polarization rotation in the enhancement of the piezoelectric properties is discussed with respect to the composition of PZT. The structure–property relationship that is revealed by this study explains the unique properties of PZT, and may be applicable in the design of new MPB-type functional materials.

Combining a perovskite ferroelectric with moderate piezoelectric properties and a nonpiezoelectric pervoskite relaxor can create a highly piezoelectric material. Here, the authors help explain this unusual result by quantifying how polar nanoregions in the material contribute to its piezoelectric response.

How materials evolve at thermal equilibrium and under external excitations at small length and time scales is crucial to the understanding and control of material properties. X-ray photon correlation spectroscopy (XPCS) at X-ray free electron laser (XFEL) facilities can in principle capture dynamics of materials that are substantially faster than a millisecond. However, the analysis and interpretation of XPCS data is hindered by the strongly fluctuating X-ray intensity from XFELs. Here we examine the impact of pulse-to-pulse intensity fluctuations on sequential XPCS analysis. We show that the conventional XPCS analysis can still faithfully capture the characteristic time scales, but with substantial decrease in the signal-to-noise ratio of the g2 function and increase in the uncertainties of the extracted time constants. We also demonstrate protocols for improving the signal-to-noise ratio and reducing the uncertainties.

Flexible rotation of spontaneous polarization at ferroelectric domain walls is predicted in theory but lacks evidence from experiment. Here, Wei et al. image a Néel-like domain wall in Ti-rich ferroelectric Pb(Zr1−xTix)O3crystals, providing insight in exploring chiral domain walls in ferroelectrics.

An In2O3/ITO thin film thermocouple was prepared via screen printing. Glass additives were added to improve the sintering process and to increase the density of the In2O3/ITO films. The surface and cross-sectional images indicate that both the grain size and densification of the ITO and In2O3 films increased with the increase in annealing time. The thermoelectric voltage of the In2O3/ITO thermocouple was 53.5 mV at 1270 °C at the hot junction. The average Seebeck coefficient of the thermocouple was calculated as 44.5 μV/°C. The drift rate of the In2O3/ITO thermocouple was 5.44 °C/h at a measuring time of 10 h at 1270 °C.

In this paper, we present a new approach to the fabrication of integrated silicon-based piezoelectric diaphragm-type biosensors by using sodium potassium niobate-silver niobate (0.82KNN-0.18AN) composite lead-free thin film as the piezoelectric layer. The piezoelectric diaphragms were designed and fabricated by micro-machining technology and chemical solution deposition. The fabricated device was very sensitive to the mass changes caused by various targets attached on the surface of diaphragm. The measured mass sensitivity value was about 931 Hz/μg. Its good performance shows that the piezoelectric diaphragm biosensor can be used as a cost-effective platform for nucleic acid testing.

X-ray photon correlation spectroscopy (XPCS) holds strong promise for observing atomic-scale dynamics in materials, both at equilibrium and during non-equilibrium transitions. Here an in situ XPCS study of the relaxor ferroelectric PbMg1/3Nb2/3O3 (PMN) is reported. A weak applied AC electric field generates strong response in the speckle of the diffuse scattering from the polar nanodomains, which is captured using the two-time correlation function. Correlated motions of the Bragg peak are also observed, which indicate dynamic tilting of the illuminated volume. This tilting quantitatively accounts for the observed two-time speckle correlations. The magnitude of the tilting would not be expected solely from the modest applied field, since PMN is an electrostrictive material with no linear strain response to the field. A model is developed based on non-uniform static charging of the illuminated surface spot by the incident micrometre-scale X-ray beam and the electrostrictive material response to the combination of static and dynamic fields. The model qualitatively explains the direction and magnitude of the observed tilting, and predicts that X-ray-induced piezoresponse could be an important factor in correctly interpreting results from XPCS and nanodiffraction studies of other insulating materials under applied AC field or varying X-ray illumination. [ABSTRACT FROM AUTHOR]