Motion of phase boundary during antiferroelectric–ferroelectric transition in a PbZrO3-based ceramic

The in situ biasing transmission electron microscopy technique is employed to investigate the nucleation and growth of the ferroelectric phase during the electric field-induced phase transition in Pb0.99{Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98}O3, a PbZrO3-based antiferroelectric ceramic. The first-order displacive phase transition is found to be highly reversible with the initial antiferroelectric domain configuration almost completely recovered upon removal of the applied field. In the forward transition from the antiferroelectric to ferroelectric phase, {100}c facets are dominant on the phase boundary; while in the reverse transition from the ferroelectric to antiferroelectric phase during bias unloading, the phase boundary is segmented into {101}c and {121}c facets. The motion of the phase boundary is nonuniform, taking the form of sequential sweeping of facet segments. The elastic distortion energy and the depolarization energy at the antiferroelectric/ferroelectric phase boundary is suggested to dictate the facet motion

Nanostructured complex oxides as a route towards thermal behavior in artificial spin ice systems

We have used soft x-ray photoemission electron microscopy to image the magnetization of single domain La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ nano-islands arranged in geometrically frustrated configurations such as square ice and kagome ice geometries. Upon thermal randomization, ensembles of nano-islands with strong inter-island magnetic coupling relax towards low-energy configurations. Statistical analysis shows that the likelihood of ensembles falling into low-energy configurations depends strongly on the annealing temperature. Annealing to just below the Curie temperature of the ferromagnetic film (T$_{C}$ = 338 K) allows for a much greater probability of achieving low energy configurations as compared to annealing above the Curie temperature. At this thermally active temperature of 325 K, the ensemble of ferromagnetic nano-islands explore their energy landscape over time and eventually transition to lower energy states as compared to the frozen-in configurations obtained upon cooling from above the Curie temperature. Thus, this materials system allows for a facile method to systematically study thermal evolution of artificial spin ice arrays of nano-islands at temperatures modestly above room temperature.Comment: 4 figures and 9 supplemental figure

Phase transition and materials design of PbZrO3-based antiferroelectric ceramics

The recent two decades witnessed a surging enthusiasm in searching for advanced functional materials, of which antiferroelectrics have gained much attention for many potential applications, especially for high-energy-density capacitors. The antiferroelectric-to-ferroelectric phase transformation process is at the heart of such applications. PbZrO3-based ceramics are still the main choice of materials due to their superb properties. In-situ transmission electron microscopy (TEM) is an advanced characterization tool for studying various nanoscale dynamic processes in real-time. External stress can influence the antiferroelectric-to-ferroelectric phase transformation. An in-situ heating TEM work in this dissertation elucidates the micromechanisms of the excellent pyroelectricity in a PbZrO3-based antiferroelectric with ZnO ceramic composite. The interaction between the antiferroelectric matrix and the second phase is observed to produce residual stresses and their impact on the ferroelectric → antiferroelectric phase transformation is directly revealed. The response of antiferroelectric with regard to electric field is a primary research interest in the antiferroelectric study. In this dissertation, an in-situ biasing TEM work on a PbZrO3-based ceramic reveals the ferroelectric phase nucleation and growth out of the antiferroelectric phase. The faceting behavior at the moving phase boundary during phase transition is observed in real space for the first time. For applications in the energy-storage capacitors, the electric hysteresis of the antiferroelectric-ferroelectric phase transition needs to be minimized for extended charge-discharge lifetime and enhanced energy efficiency. Guided by the concept of relaxor antiferroelectrics, a novel doping scheme, equal molar fraction co-doping of Li+ and Bi3+, is demonstrated in an antiferroelectric PbZrO3-based ceramic. Strong relaxor characteristics are imparted, and electric hysteresis is significantly suppressed and ultrahigh energy efficiency (94%) is realized

Structure, ferroelectric, and dielectric properties of (Na1−2xCax)NbO3 ceramics

Mimicking the scheme of incorporating La3+ to Pb(Zr1−xTix)O3, Ca2+ is used to substitute Na+ in the lead-free NaNbO3 compound, with A-site vacancy introduced to maintain charge neutrality. The anticipated relaxor behavior is expected to suppress the remanent polarization and improve the energy storage properties of NaNbO3-based ceramics. Specifically, (Na1−2xCax)NbO3 (x = 0.01, 0.02, 0.04, 0.08) ceramics were prepared with the solid-state method, and their structures and electric properties were investigated. X-ray diffraction and transmission electron microscopy reveal the existence of minor amount of CaNb2O6 second phase. Polarization vs. electric field hysteresis loop measurements verify the suppression of remanent polarization in compositions of x ≤ 0.04. The temperature-dependent dielectric tests indicate that both the relaxation and diffuseness parameters monotonically increase with Ca2+ content. The results demonstrate that the introduction of a smaller donor dopant and charge-compensating vacancies on the A-site in NaNbO3 is an effective strategy to disrupt the long-range dipole order.This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1557/s43578-020-00020-5. Copyright 2021 The Author(s), under exclusive licence to The Materials Research Society 2021. Posted with permission

Phase transition and materials design of PbZrO3-based antiferroelectric ceramics

The recent two decades witnessed a surging enthusiasm in searching for advanced functional materials, of which antiferroelectrics have gained much attention for many potential applications, especially for high-energy-density capacitors. The antiferroelectric-to-ferroelectric phase transformation process is at the heart of such applications. PbZrO3-based ceramics are still the main choice of materials due to their superb properties. In-situ transmission electron microscopy (TEM) is an advanced characterization tool for studying various nanoscale dynamic processes in real-time. External stress can influence the antiferroelectric-to-ferroelectric phase transformation. An in-situ heating TEM work in this dissertation elucidates the micromechanisms of the excellent pyroelectricity in a PbZrO3-based antiferroelectric with ZnO ceramic composite. The interaction between the antiferroelectric matrix and the second phase is observed to produce residual stresses and their impact on the ferroelectric → antiferroelectric phase transformation is directly revealed. The response of antiferroelectric with regard to electric field is a primary research interest in the antiferroelectric study. In this dissertation, an in-situ biasing TEM work on a PbZrO3-based ceramic reveals the ferroelectric phase nucleation and growth out of the antiferroelectric phase. The faceting behavior at the moving phase boundary during phase transition is observed in real space for the first time. For applications in the energy-storage capacitors, the electric hysteresis of the antiferroelectric-ferroelectric phase transition needs to be minimized for extended charge-discharge lifetime and enhanced energy efficiency. Guided by the concept of relaxor antiferroelectrics, a novel doping scheme, equal molar fraction co-doping of Li+ and Bi3+, is demonstrated in an antiferroelectric PbZrO3-based ceramic. Strong relaxor characteristics are imparted, and electric hysteresis is significantly suppressed and ultrahigh energy efficiency (94%) is realized

Phase transition and materials design of PbZrO3-based antiferroelectric ceramics

The recent two decades witnessed a surging enthusiasm in searching for advanced functional materials, of which antiferroelectrics have gained much attention for many potential applications, especially for high-energy-density capacitors. The antiferroelectric-to-ferroelectric phase transformation process is at the heart of such applications. PbZrO3-based ceramics are still the main choice of materials due to their superb properties. In-situ transmission electron microscopy (TEM) is an advanced characterization tool for studying various nanoscale dynamic processes in real-time. External stress can influence the antiferroelectric-to-ferroelectric phase transformation. An in-situ heating TEM work in this dissertation elucidates the micromechanisms of the excellent pyroelectricity in a PbZrO3-based antiferroelectric with ZnO ceramic composite. The interaction between the antiferroelectric matrix and the second phase is observed to produce residual stresses and their impact on the ferroelectric → antiferroelectric phase transformation is directly revealed. The response of antiferroelectric with regard to electric field is a primary research interest in the antiferroelectric study. In this dissertation, an in-situ biasing TEM work on a PbZrO3-based ceramic reveals the ferroelectric phase nucleation and growth out of the antiferroelectric phase. The faceting behavior at the moving phase boundary during phase transition is observed in real space for the first time. For applications in the energy-storage capacitors, the electric hysteresis of the antiferroelectric-ferroelectric phase transition needs to be minimized for extended charge-discharge lifetime and enhanced energy efficiency. Guided by the concept of relaxor antiferroelectrics, a novel doping scheme, equal molar fraction co-doping of Li+ and Bi3+, is demonstrated in an antiferroelectric PbZrO3-based ceramic. Strong relaxor characteristics are imparted, and electric hysteresis is significantly suppressed and ultrahigh energy efficiency (94%) is realized

Phase transition and materials design of PbZrO3-based antiferroelectric ceramics

The recent two decades witnessed a surging enthusiasm in searching for advanced functional materials, of which antiferroelectrics have gained much attention for many potential applications, especially for high-energy-density capacitors. The antiferroelectric-to-ferroelectric phase transformation process is at the heart of such applications. PbZrO3-based ceramics are still the main choice of materials due to their superb properties. In-situ transmission electron microscopy (TEM) is an advanced characterization tool for studying various nanoscale dynamic processes in real-time. External stress can influence the antiferroelectric-to-ferroelectric phase transformation. An in-situ heating TEM work in this dissertation elucidates the micromechanisms of the excellent pyroelectricity in a PbZrO3-based antiferroelectric with ZnO ceramic composite. The interaction between the antiferroelectric matrix and the second phase is observed to produce residual stresses and their impact on the ferroelectric → antiferroelectric phase transformation is directly revealed. The response of antiferroelectric with regard to electric field is a primary research interest in the antiferroelectric study. In this dissertation, an in-situ biasing TEM work on a PbZrO3-based ceramic reveals the ferroelectric phase nucleation and growth out of the antiferroelectric phase. The faceting behavior at the moving phase boundary during phase transition is observed in real space for the first time. For applications in the energy-storage capacitors, the electric hysteresis of the antiferroelectric-ferroelectric phase transition needs to be minimized for extended charge-discharge lifetime and enhanced energy efficiency. Guided by the concept of relaxor antiferroelectrics, a novel doping scheme, equal molar fraction co-doping of Li+ and Bi3+, is demonstrated in an antiferroelectric PbZrO3-based ceramic. Strong relaxor characteristics are imparted, and electric hysteresis is significantly suppressed and ultrahigh energy efficiency (94%) is realized

In situ TEM observation on the ferroelectric-antiferroelectric transition in Pb(Nb,Zr,Sn,Ti)O3/ZnO

Ceramic composites of (1-x)Pb0.99{Nb0.02[(Zr0.57Sn0.43)0.937Ti0.063]0.98}O3 (PNZST)/xZnO were recently reported to exhibit exceptionally high pyroelectric coefficients near human body temperature due to the ferroelectric-antiferroelectric transition of the matrix grains. In the present work, a comparative study is conducted on two composites of x = 0.1 and 0.4 with in situ heating transmission electron microscopy (TEM). The results verify the presence of strain field in the PNZST grain adjacent to a ZnO particle and the stabilized ferroelectric phase at room temperature in the composite of x = 0.1. During heating, the ferroelectric matrix grain transforms to the antiferroelectric phase, contributing to the pyroelectric effect. In the composite of x = 0.4, high-angle annular dark-field imaging combined with energy-dispersive X-ray spectroscopy reveal the existence of both ZnO and Zn2SnO4. The formation of Zn2SnO4 indicates that Sn in the PNZST matrix grain is selectively extracted, and decomposition of the perovskite phase has taken place. The decomposition products in the form of fine particles are observed to facilitate the nucleation of the antiferroelectric phase and restrict the motion of the phase boundary during heating. The larger amount of ZnO and Zn2SnO4 and the decomposition of the PNZST perovskite phase are suggested to be responsible for the much lower pyroelectric coefficient in the x = 0.4 composite.This is the peer-reviewed version of the following article: Liu, Binzhi, Ling Li, Shan‐Tao Zhang, Lin Zhou, and Xiaoli Tan. "In situ TEM observation on the ferroelectric‐antiferroelectric transition in Pb (Nb, Zr, Sn, Ti) O3/ZnO." Journal of the American Ceramic Society 105, no. 2 (2022): 794-800, which has been published in final form at DOI: 10.1111/jace.18148. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Copyright 2021 The American Ceramic Society. Posted with permission

Motion of phase boundary during antiferroelectric–ferroelectric transition in a PbZrO3-based ceramic

The in situ biasing transmission electron microscopy technique is employed to investigate the nucleation and growth of the ferroelectric phase during the electric field-induced phase transition in Pb0.99{Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98}O3, a PbZrO3-based antiferroelectric ceramic. The first-order displacive phase transition is found to be highly reversible with the initial antiferroelectric domain configuration almost completely recovered upon removal of the applied field. In the forward transition from the antiferroelectric to ferroelectric phase, {100}c facets are dominant on the phase boundary; while in the reverse transition from the ferroelectric to antiferroelectric phase during bias unloading, the phase boundary is segmented into {101}c and {121}c facets. The motion of the phase boundary is nonuniform, taking the form of sequential sweeping of facet segments. The elastic distortion energy and the depolarization energy at the antiferroelectric/ferroelectric phase boundary is suggested to dictate the facet motion.This article is published as Liu, Binzhi, Xinchun Tian, Lin Zhou, and Xiaoli Tan. "Motion of phase boundary during antiferroelectric–ferroelectric transition in a PbZrO3-based ceramic." Physical Review Materials 4, no. 10 (2020): 104417. DOI: 10.1103/PhysRevMaterials.4.104417. Posted with permission.</p

Atomic layer molecular beam epitaxy of kagome magnet RMn6Sn6 (R = Er, Tb) thin films

Kagome lattices have garnered substantial interest because their band structure consists of topological flat bands and Dirac cones. The RMn6Sn6 (R = rare earth) compounds are particularly interesting because of the existence of the large intrinsic anomalous Hall effect (AHE), which originates from the gapped Dirac cones near the Fermi level. This makes RMn6Sn6 an outstanding candidate for realizing the high-temperature quantum AHE. The growth of RMn6Sn6 thin films is beneficial for both fundamental research and potential applications. However, most of the studies on RMn6Sn6 have focused on bulk crystals, and the synthesis of RMn6Sn6 thin films has not been reported so far. Here, we report the atomic layer molecular beam epitaxy growth, structural and magnetic characterizations, and transport properties of ErMn6Sn6 and TbMn6Sn6 thin films. It is especially noteworthy that TbMn6Sn6 thin films have out-of-plane magnetic anisotropy, which is important for realizing the quantum AHE. Our work paves the avenue toward the control of the AHE using devices patterned from RMn6Sn6 thin films