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BACKGROUND Evidence regarding the analgesic effect of distraction through immersion in virtual reality (VR) for care-induced pain, has been documented in several phase II trials but comparison with standard treatments in large-randomized studies are needed. OBJECTIVE In this open-label multicenter randomized phase III trial (ClinicalTrials.gov identifier: NCT 03483194), we evaluated the safety and efficacy of a novel VR therapy solution for distraction in the context of bone marrow (BM) biopsy. METHODS Bliss© is a VR software with four imaginary interactive environments in three dimensions with a binaural sound (head-mounted display). Efficacy was evaluated on pain intensity using a visual analog scale (score from 0-10) immediately after the biopsy. The primary endpoint was patient-assessed pain intensity after BM procedure, with a visual analog scale (VAS). Secondary endpoints were anxiety and tolerance. Overall, 126 patients with previously documented untreated or suspected malignant hemopathy between September 6, 2018, and May 18, 2020, were randomly assigned in a 1:1 ratio to receive pain prevention with a mixture of nitrous oxide/oxygen (MEOPA) (n=63) or VR (n=63) before and during BM biopsy. All patients received local anesthesia (lidocaine) before biopsy. Modified intention-to-treat analysis was performed. RESULTS Participants’ median age was 65.5 (range 18-87) years and 54.2% of patients were male. The average pain intensity was 3.5 (SD 2.6) for the MEOPA group and 3.0 (SD 2.4) for the VR group without any significant difference in age, sex, center or hemopathy (P=.26). Concerning anxiety, 67.5% of patients were afraid before the biopsy and anxiety scores were moderate to very high in 26.3% of patients before the biopsy (fear of pain and revised STAI questionnaires) and 9.0% after the biopsy for all patients without any significant difference between the 2 groups (P=.83). Immersion in VR was well tolerated by the majority of patients in the VR group. CONCLUSIONS The intensity of pain and did not significantly differ between both arms. VR was well tolerated, and satisfaction of patients, nurses and physicians was very high. Virtual reality could be an alternative treatment in case of contraindication or intolerance to MEOPA. CLINICALTRIAL ClinicalTrials.gov identifier: NCT 03483194

International audience; Phase diagram of the solid solution system K 0.5 Na 0.5 NbO 3-Bi ½ Na ½ TiO 3 [(1-x)KNN-xBNT] has been established from dielectric permittivity measurement and structure analyses. The unit cell volumes continuously decrease depending on the composition, while the local structure maintains distortions away from the cubic average structure in the range 0.10 ≤ x ≤ 0.90. No clear correspondence for the temperatures of phase transition exists between structural studies and physical properties. The dielec-tric behavior is depicted successively from normal ferroelectric, diffuse phase transition, re-entrant-like relaxor, relaxor + dipolar glass-like relaxor, BNT-like relaxor with the increase of BNT. A comprehensive composition-property phase diagram for this system has been given to understand the various ferro-electric phenomena. The result could be mainly elucidated by the nanoclusters and the disorder driven nucleation of polar nanoregions contributed by a valence mismatch at one of the cation sites.

The influence of B-site disorder on the dielectric, microstructural, and structural characteristics of unpoled, lead-free (Bi1/2Na1/2)TiO3-0.06Ba(ZrxTi1-x)O3 piezoelectric ceramics with x = 0.02, 0.10, and 0.15 was investigated. The low and medium doping level introduced a stabilization of polar nanoregions reflected in the shift of the dispersive permittivity anomalies to higher temperatures and the development of lamellar rhombohedral domains embedded in the prevalent tetragonal nanodomain matrix. For higher Zr level, the regions of lamellar domains remain, but the dielectric characteristics indicate a reduction in the previous stabilization effect. This behavior is rationalized by a reduction in the correlation length due to the increasing amount of nonpolar sample volume with increasing Zr addition.

The phase diagram of the lead-free piezoelectric (1 − x)K0.5Na0.5NbO3–xBi1/2Na1/2TiO3 system has been studied by high-resolution synchrotron powder diffraction, neutron powder diffraction and selected area electron diffraction. The two lead-free piezoelectric materials K0.5Na0.5NbO3 and Bi1/2Na1/2TiO3 form an infinite substitution solid solution. The orthorhombic (O), monoclinic (M), tetragonal (T) and rhombohedral (R) phases and the phase coexistence of M (Pm) + T (P4mm) for 0.02 < x ≤ 0.14, T (P4bm) + pseudocubic (Pm{\overline 3}m) for 0.14 < x ≤ 0.87 and T (P4bm) + R (R3c) for 0.87 < x ≤ 0.96 have been investigated at room temperature, with a subtle change in the structure observed. The oxygen octahedral tilt system has been mapped as a function of composition and temperature. The results indicate that K0.5Na0.5NbO3–Bi1/2Na1/2TiO3 does not display a morphotropic phase boundary like lead zirconate titanate, and that the most significant structural changes as a function of composition occur near x = 0.14 and x = 0.87 as a result of ionic disorder at the A and B sites in the perovskite ABO3 structure at room temperature.

The design of core–shell materials affords additional degrees of freedom to tailor functional properties as compared to solid solution counterparts. Although to date most of the work in core–shell materials has focused on dielectrics, piezoelectric core–shell ceramics may gain similar interest. Generalities of core–shell functional ceramics features are addressed in this work. A model system, Bi1/2Na1/2TiO3–SrTiO3, is introduced to discuss structure–property relationships. We demonstrate that this system features a core–shell microstructure for the composition corresponding to 25 at.% Sr. The material is studied by means of macroscopic functional properties and in situ structural characterization techniques at different length scales, such as X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The evolution of the core–shell with field and temperature determines its functional properties. The high strain of the system, ~0.3% at 4 kV/mm, is due to an electric-field-induced phase transition of the core and shell. Upon field removal the core remains in a poled state, whereas the shell is characterized by a reversible transformation. The reversibility of the phase transition of shells and associated switching are key features in the observed giant strain. Dielectric anomalies are found to be related to changes in oxygen octahedral tilting angles within the core and shell.

The influence of heat treatment in lead zirconate titanate Pb(Zr,Ti)O3 (PZT) ferroelectrics on the domain structure and strain behavior has been investigated. Temperature-induced changes in the domain configuration, for example, appearance of nanodomains within microdomains, were observed by in situ hot-stage transmission electron microscopy. During the transient post annealing state the strain behavior under electric field differed from that of the nonheat-treated ferroelectrics. Directly after cooling the difference was most pronounced and decreased as a function of time. The enhanced response to an electric field of 4 kV/mm resulted in qualitatively different effects on strain for PZT from the tetragonal side and from the rhombohedral side of the morphotropic phase boundary.

In this study, the domain structure, bimodality of domains and wedge-shape formation of domain tips are investigated in tetragonal Pb[Zr0.375Ti0.625]O3 and Pb[Zr0.45Ti0.55]O3 ferroelectrics by transmission electron microscopy (TEM). Finite element method (FEM) calculations predicted the stability of the experimentally observed domain configuration for different boundary conditions concerning electrical as well as mechanical state. Detailed TEM studies of a specific bimodal domain configuration, composed of four different domains, revealed the presence of a domain wall with alternating tiny head-to-side and tail-to-side arrays and broad head-to-tail areas. The experimentally observed existence of both, wedge-shaped domain tips and bimodality, could be rationalized either by the presence of charges or by shear stress as evidenced by FEM calculations.

Recently developed lead-free incipient piezoceramics are promising candidates for off-resonance actuator applications with their exceptionally large electromechanical strains. Their commercialization currently faces two major challenges: high electric field required for activating the large strains and large strain hysteresis. It is demonstrated that design of a relaxor/ferroelectric composite provides a highly effective way to resolve both challenges. Experimental results in conjunction with numerical simulations provide key parameters for the development of viable incipient piezoceramics.

Coupling of order parameters provides a means to tune functionality in advanced materials including multiferroics, superconductors, and ionic conductors. We demonstrate that the response of a frustrated ferroelectric state leads to coupling between order parameters under electric field depending on grain orientation. The strain of grains oriented along a specific crystallographic direction, ⟨h00⟩, is caused by converse piezoelectricity originating from a ferrodistortive tetragonal phase. For ⟨hhh⟩ oriented grains, the strain results from converse piezoelectricity and rotostriction, as indicated by an antiferrodistortive instability that promotes octahedral tilting in a rhombohedral phase. Both strain mechanisms combined lead to a colossal local strain of (2.4 ± 0.1) % and indicate coupling between oxygen octahedral tilting and polarization, here termed “rotopolarization”. These findings were confirmed with electromechanical experiments, in situ neutron diffraction, and in situ transmission electron microscopy in 0.75Bi1/2Na1/2TiO3-0.25SrTiO3. This work demonstrates that polar and non-polar instabilities can cooperate to provide colossal functional responses This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0

Structure and phase transitions of (1 − y)((1 − x)Bi1/2Na1/2TiO3–xBi1/2K1/2TiO3)–yK0.5Na0.5NbO3 (x; y) piezoceramics (0.1 ≤ x ≤ 0.4; 0 ≤ y ≤ 0.05) were investigated by transmission electron microscopy, neutron diffraction, temperature-dependent x-ray diffraction, and Raman spectroscopy. The local crystallographic structure at room temperature (RT) does not change by adding K0.5Na0.5NbO3 to Bi1/2Na1/2TiO3–xBi1/2K1/2TiO3 for x = 0.2 and 0.4. The average crystal structure and microstructure on the other hand develop from mainly long-range polar order with ferroelectric domains to short-range order with polar nanoregions displaying a more pronounced relaxor character. The (0.1; 0) and (0.1; 0.02) compositions exhibit monoclinic Cc space group symmetry, which transform into Cc + P4bm at 185 and 130 °C, respectively. This high temperature phase is stable at RT for the morphotropic phase boundary compositions of (0.1; 0.05) and all compositions with x = 0.2. For the compositions of (0.1; 0) and (0.1; 0.02), local structural changes on heating are evidenced by Raman; for all other compositions, changes in the long-range average crystal structure were observed.

LiCoPO4-coated disordered carbon nanofibers (CNFs/LiCoPO4) were obtained by a sol–gel method, using triethyl phosphite or triethyl phosphate as the phosphorous source. The crystal structure of the products was analyzed by X-ray powder diffraction, while morphology was studied using scanning electron microscopy, transmission electron microscopy, Auger electron spectroscopy and X-ray photoelectron spectroscopy. Optimal synthesis conditions for the CNFs/LiCoPO4 in light of the best electrochemical performance are discussed. The best discharge capacity 105 mAh/g (or ca. 63% of the theoretical capacity) shows the material with 40% CNFs/LiCoPO4 and addition coating by carbon black. This composition has a best purity of active materials and point coverage of CNFs. The X-ray photoelectron C1s spectra of the CNFs surface without and with sputter erosion show enhancement of C–O bonds at the fiber surface, which does not influence significantly electrochemical behavior of the composite materials.

The temperature- and field-dependent degradation properties of bulk Pb(Zr,Ti)O3 material (PZT) under a unipolar electric field were investigated. Unipolar cycling leads to the build-up of an internal bias field based on the agglomeration of charges at grain boundaries. A simple model was developed which describes the general dynamics of unipolar fatigue and its dependence on temperature and driving field. Comparing the large and small signal permittivity before and after fatigue led to the conclusion that domain walls became clamped by the agglomerated charges. This clamping effect could be visualized by transmission electron microscopy (TEM). Additionally, the TEM investigations revealed that unipolar fatigue leads to a weakening of the microstructure and to the development of microcracks.

Hybrid materials composed of LiMPO4 (M = Fe or Co) with multiwalled carbon nanotubes (MCNTs) were synthesized by tethering lithium phosphoolevins on isolated stochastically disordered MWCNTs as well as on ordered 3D MWCNT arrays via solution based impregnation routes. Ordered 3D arrays of MWCNT monoliths comprising MWCNTs with nominal tube diameters of 60 and 200 nm were synthesized by a catalyst free, template based method, with porous aluminum oxide (PAOX) acting as a template. Consecutive selectiveetching processes gave free standing aligned 3D carbon nanotube (CNT) architectures that were used as supporting cathode structures for electroactive LiCoPO4. LiCoPO4 nanoparticle suspensions derived from an ethanol based organic phosphate source turned out to be superior for the tethering of LiCoPO4 nanoparticles onto the 3D aligned CNT arrays compared to an aqueous based tethering route, thus giving hybrid materials with better electrochemical battery performance compared to materials generated by the latter method. Li ion extraction within the ordered 3D CNT/LiCoPO4 composites seems to be a two-step process and the Li intercalation a one-step process, highlighting the enhanced kinetics of the Li insertion process in the 3D CNT/LixCoPO4 composite in comparison to a particulate mixture of LixCoPO4 that is typically present in a conventional carbon/LiCoPO4 cathode composite system.

In this study, recent results from our electron, X-ray, and neutron-diffraction experiments with emphasis on the binary Bi1/2Na1/2TiO3-BaTiO3 (BNT–BT) and ternary Bi1/2Na1/2TiO3–BaTiO3–K0.5Na0.5NbO3 (BNT–BT–KNN) system are presented and contrasted with literature. The experimental results clearly revealed a phase coexistence on the nanoscale level. A systematic study of superlattice reflections in conjunction with microstructural characteristics showed that the BNT-based systems have specific properties in common, which, however, strongly depend on composition. In situ transmission electron microscopy (TEM) electric field experiments unequivocally demonstrated the evolution of lamellar domains. Combining in situ TEM results with published in situ neutron-diffraction experiments, we proposed an electric field-induced phase transition that results in the giant unipolar and bipolar strain observed in specific compositions of the ternary system.

A comparative study of two distinct lead-free piezoceramics, (Bi0.5Na0.5TiO3)0.92–(BaTiO3)0.06–(K0.5Na0.5NbO3)0.02and (Bi0.5Na0.5TiO3)0.94–(BaTiO3)0.05–(K0.5Na0.5NbO3)0.01, termed 92-06-02 and 94-05-01, respectively, is presented. The samples were investigated by complementary diffraction techniques, namely X-ray, neutron and electron diffraction. Transmission electron microscopy (TEM) and powder diffraction experiments clearly revealed the presence of both rhombohedral and tetragonal phases in space groupsR3candP4bm, respectively. Superlattice reflections observed in the diffraction patterns were used to identify the two phases. It was found that sample 92-06-02, with a high proportion of the nonpolar tetragonal phase, shows a grainy contrast, whereas specimen 94-05-01 features domain-like contrast, related to a higher rhombohedral phase fraction. The combination of local scale analysesviaTEM with X-ray and neutron diffraction provides the experimental basis for further structural investigations.

In this letter, conclusive experimental evidence is presented for the coexistence of two phases within individual grains in the system ( Bi 0.5 Na 0.5 TiO 3)0.91-( BaTiO 3)0.06-( K 0.5 Na 0.5 NbO 3)0.03. Electron diffraction data unequivocally reveal the presence of a rhombohedral and a tetragonal phase with space group R3c and P4bm, respectively, both on the nanoscale level. Superlattice reflections, observed in the corresponding selected area electron diffraction, were used to identify the rhombohedral and tetragonal phase present at different regions within one grain. It is thought that the rhombohedral phase acts as a nucleation site for the phase transformation monitored under applied electrical field. The coexistence of these two phases in conjunction with the triggered tetragonal to rhombohedral phase transformation rationalizes the high bipolar and unipolar strain recorded for this lead-free ferroelectric material.

The domain structure of Pb(Zr0.52Ti0.48)O3 before and after hot-stage experiment has been studied. The influence of maximum temperature, heating and cooling rate on the domain configuration of Pb(Zr1− x , Ti x )O3 with x = 0.40, 0.45, 0.48 and 0.55 was analysed. A reliable basis for further hot-stage experiments of Pb(Zr1−x, Tix)O3 has been established. The investigations revealed a temperature dependent appearance and disappearance of nano- and microdomains. The appearance of microdomains in the nano scale range during cooling, denoted as domain miniaturisation, and the time dependent recovering of the former domain structure, revealed that under specific experimental conditions the domain configuration is reversible.

Applications ranging from microphones to AFM transducers exploit the interplay between mechanical stress and electric field arising from structural transitions in certain perovskite oxides. The classic material contains lead, however, and efficient, environmentally friendly alternatives have long been sought. The authors use a challenging technique to visualize the real-time microstructural evolution of a lead-free ferroelectric system, and the multidomain states and transitions they find are expected to inform the search for additional systems, as well as the applications that will rely on them.

The nature of the cubic-like state in the lead-free piezoelectric ceramics 0.5K0.5Na0.5NbO3-0.5Na0.5Bi0.5TiO3 (KNN-50BNT) has been examined in detail by synchrotron x-ray diffraction (SD), selected area electron diffraction (SAED), neutron diffraction (ND), and temperature dependent dielectric characterization. The SD pattern of KNN-50BNT presents a pure perovskite structure with pseudocubic symmetry. However, superlattice reflections were observed by SAED and completely indexed by tetragonal symmetry with P4bm space group in ND pattern. The relaxor behavior of KNN-50BNT is compared with Pb-based and Ba-based relaxors and discussed in the framework of the Vogel-Fulcher law and the new glass model. The KNN-50BNT ceramic exhibits the strongest dielectric dispersion among them., 20 pages, 4 figures, 3 tables

Transmission electron microscopy has been used to investigate the junction between two lamellar bands in a tetragonal lead zirconate titanate (PZT) ceramic. It is found that significant bending occurs in the area due to the matching of different domains on planes. Analysis of CBED patterns shows that the orientation relationships between the long boundaries between lamellae is much as expected and allows quantification of local c/a ratios. The short boundaries at the band junction, however, are highly stressed and deviate significantly from ideal misorientation values. This reveals that the areas between the 4- domain junctions in the band junction are highly stressed with peak stresses in the GPa range, which are highly likely to function as the source of microcracks under the additional strains found in device application.

Undoped Pb[ZrxTi1-x]O3 (PZT) ceramics from the tetragonal and rhombohedral side of the morphotropic phase boundary (MPB) were examined. Temperature dependent changes in domain configuration were observed by in situ hot-stage transmission electron microscopy (TEM). In corresponding macroscopic ex situ strain measurements an enhanced influence of the electric field was detected after annealing.

The structural behavior of ceramic solid solutions (1\ensuremath{-}$x$)Na${}_{1/2}$Bi${}_{1/2}$TiO${}_{3}$--$x$K${}_{1/2}$Bi${}_{1/2}$TiO${}_{3}$ (NBT-KBT) was studied using high-resolution powder diffraction and transmission electron microscopy. A temperature-independent morphotropic phase boundary (MPB) separating NBT-like pseudorhombohedral (R) and KBT-like pseudotetragonal (T) phases was observed at $x$ \ensuremath{\approx} 0.2. For $xl0.2$, both local and average room-temperature structures are similar to those in NBT. Simultaneous long-range antiphase and short-range in-phase octahedral rotations average, resulting in effective antiphase ${a}^{\ensuremath{-}}{a}^{\ensuremath{-}}{c}^{\ensuremath{-}}$ tilting, which yields monoclinic symmetry when probed by x-ray diffraction (XRD). For these compositions, polar ordering is coupled to antiphase octahedral rotations so that tilting and ferroelectric (FE) domains coincide. Compositions with $xg0.2$ exhibit a tetragonal-like distortion; however, complex splitting of reflections in XRD patterns suggests that the actual symmetry is lower than tetragonal. For $0.2\ensuremath{\le}x\ensuremath{\le}0.5$, in-phase octahedral tilting ${a}^{0}{b}^{+}{a}^{0}$ (or ${a}^{+}{b}^{0}{b}^{0}$) is present but confined to the nanoscale, while for $xg0.5$ the structure becomes untilted. In-phase tilting evolves above the ferroelectric transition and occurs around a nonpolar ($a$ or $b$) axis of the average T structure. The onset of polar order has no significant effect on the coherence length of in-phase tilting, which suggests only weak coupling between the two phenomena. The average symmetry of the T phase is determined by the effective symmetry (Imm2) of assemblages of coherent in-phase tilted nanodomains. Near the MPB, the coexistence of extended R- and T-like regions is observed, but lattice distortions within each phase are small, yielding narrow peaks with a pseudocubic appearance in XRD. The temperature of the FE phase transition exhibits a minimum at the MPB. The structured diffuse scattering observed in electron diffraction patterns for all the compositions suggests that polar order in NBT-KBT solid solutions is modulated away from the average displacements refined using powder diffraction data.

Este estudo teve como objetivo comparar escores de desempenho motor, antes e após sessões de hipoterapia através da escala de Medida da Função Motora Grossa (GMFM). Como método, foi realizado um estudo quantitativo descritivo de intervenção do tipo antes e depois, com 3 casos de paralisia cerebral (PC),de ambos os sexos, com idades entre 5 e 7 anos, escolhidos de forma não probabilista, com quadro motor de quadriplegia mista. Foi obtida, como resultado, FAB, RFC e BES apresentaram melhora de 88.35%, 96% e 31%, respectivamente na dimensão A deitar e rola e 16.65%, 31.66% e 33% na dimensão B: sentar. RFC e BES também apresentaram melhoras na dimensão C: engatinhar e ajoelhar de 2.38% e 40.47%, respectivamente. Este estudo conclui que indivíduos com PC melhoram controle de tronco e cervical, sendo que com os índices da escala GMFM foi possível quantificar os ganhos motores.

Este estudo teve como objetivo comparar escores de desempenho motor, antes e apos sessoes de hipoterapia atraves da escala de Medida da Funcao Motora Grossa (GMFM). Como metodo, foi realizado um estudo quantitativo descritivo de intervencao do tipo antes e depois, com 3 casos de paralisia cerebral (PC),de ambos os sexos, com idades entre 5 e 7 anos, escolhidos de forma nao probabilista, com quadro motor de quadriplegia mista. Foi obtida, como resultado, FAB, RFC e BES apresentaram melhora de 88.35%, 96% e 31%, respectivamente na dimensao A deitar e rola e 16.65%, 31.66% e 33% na dimensao B: sentar. RFC e BES tambem apresentaram melhoras na dimensao C: engatinhar e ajoelhar de 2.38% e 40.47%, respectivamente. Este estudo conclui que individuos com PC melhoram controle de tronco e cervical, sendo que com os indices da escala GMFM foi possivel quantificar os ganhos motores.

The nature of the cubic-like state in the lead-free piezoelectric ceramics 0.5K0.5Na0.5NbO3-0.5Na1/2Bi1/2TiO3 (KNN-50BNT) has been examined in detail by synchrotron x-ray diffraction (SD), selected-area electron diffraction (SAED), neutron diffraction (ND), and temperature-dependent dielectric characterization. The SD pattern of KNN-50BNT presents a pure perovskite structure with pseudocubic symmetry. However, superlattice reflections were observed by SAED and completely indexed by tetragonal symmetry with P4bm space group in ND pattern. The relaxor behavior of KNN-50BNT is compared with Pb-based and Ba-based relaxors and discussed in the framework of the Vogel-Fulcher law and the new glass model. The KNN-50BNT ceramic exhibits the strongest dielectric dispersion among them.

Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. This review describes recent developments in the synthesis and characterization of composites which consist of lithium metal phosphates (LiMPO(4), M = Fe, Co, Ni, Mn) coated on nanostructured carbon architectures (unordered and ordered carbon nanotubes, amorphous carbon, carbon foams). The major goal of this review is to highlight new progress in using different three dimensional nanostructured carbon architectures as support for the phosphate based cathode materials (e.g.: LiFePO(4), LiCoPO(4)) of high electronic conductivity to develop lithium batteries with high energy density, high rate capability and excellent cycling stability resulting from their huge surface area and short distance for mass and charge transport.

Ferroelectric materials play an important role in today’s functional material discussion and are widely used in industrial applications as injection systems, actuators or sensors. A detailed knowledge of the microstructure is prerequisite to optimise these materials for further applications.

Lead zirconate titanate (PZT) materials are widely used in industrial applications like fuel injectors or actuators. The possible environmental problems caused by the lead content of the conventional devices drives the need to replace lead-based systems by new, nontoxic components. However, those novel materials have to compete with the electrical and mechanical properties of to days PZT.

In recent years, the stability field of a monoclinic phase at the morphotropic phase boundary in lead zirconate titanate, $\mathrm{Pb}[{\mathrm{Zr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}]{\mathrm{O}}_{3}$, has been under discussion. In the present study, we investigated samples in the compositional range between $0.40\ensuremath{\leqslant}x\ensuremath{\leqslant}0.475$ and $x=0.55$ using high-resolution synchrotron x-ray diffraction in combination with transmission electron microscopy and electron paramagnetic resonance to correlate average structure and microstructural information. It is shown that the microstructure plays a crucial role in the analysis of diffraction data. The appearance of intensity in diffraction patterns formerly linked to a monoclinic phase [B. Noheda et al., Phys. Rev. B 61, 8687 (2000)] can directly be correlated to a miniaturization of the average domain structure of the material visible in the presence of nanodomains. The internal symmetry of the nanodomains is not necessarily monoclinic due to coherence effects in diffraction and is discussed with respect to martensitic theory.

The outstanding piezoelectric properties of lead zirconate titanate (PZT) ceramics with compositions close to the morphotropic phase boundary of the quasibinary phase diagram of lead zirconate and lead titanate are still under debate. A combination of ex situ and in situ transmission electron microscopy and high resolution x-ray diffraction revealed that the extrinsic piezoelectric effect in morphotropic PZT is closely connected to the existence of nanodomains. The in situ transmission electron microscopy investigations with applied electric field show that mainly the nanodomains respond to the electric field while the microdomain structure does not change noticeably in our experiments.

In this study, the evolution of field induced mechanisms in lead-free piezoelectric ceramics (1−x)Bi1/2 Na 1/2TiO3-xBaTiO3 with x = 0.06 and 0.07 was investigated by transmission electron microscopy, neutron, and X-ray diffraction. Preliminary investigations revealed a strong degradation of macroscopic electromechanical properties within the first 100 bipolar electric cycles. Therefore, this structural investigation focuses on a comparative diffraction study of freshly prepared, poled, and fatigued specimens. Transmission electron microscopy and neutron diffraction of the initial specimens reveal the coexistence of a rhombohedral and a tetragonal phase with space group R3c and P4bm, respectively. In situ electric field X-ray diffraction reveals a pronounced field induced phase transition from a pseudocubic state to a phase composition of significantly distorted phases upon poling with an external electric field of 4 kV/mm. Although the structures of the two compositions are pseudocubic and almost indistinguishable in the unpoled virgin state, the electric field response shows significant differences depending on composition. For both compositions, the application of an electric field results in a field induced phase transition in the direction of the minority phase. Electric cycling has an opposite effect on the phase composition and results in a decreased phase fraction of the minority phase in the fatigued remanent state at 0 kV/mm.

In this work, the lead-free Ba(Zr0.2Ti0.8)O3-0.3(Ba0.7Ca0.3)TiO3 piezoelectric ceramic was investigated in situ under an applied electric field by transmission electron microscopy. Significant changes in domain morphology of the studied material have been observed under an applied electric field. During the poling process, the domain configurations disappeared, forming a single-domain state. This multi- to single-domain state transition occurred with the formation of an intermediate nanodomain state. After removing the electric field, domain configurations reappeared. Selected area electron diffraction during electrical poling gave no indication of any structural changes as for example reflection splitting. Rather, a contribution of the extrinsic effect to the piezoelectric response of the Ba(Zr0.2Ti0.8)O3-0.3(Ba0.7Ca0.3)TiO3 was found to be dominant.

Temperature-dependent dielectric permittivity of 0.94(Bi1/2Na1/2)TiO3-0.06BaTiO3 (BNT-6BT) lead-free piezoceramics was studied to disentangle the existing unclear issues over the crystallographic aspects and phase stability of the system. Application of existing phenomenological relaxor models enabled the relaxor contribution to the entire dielectric permittivity spectra to be deconvoluted. The deconvoluted data in comparison with the temperature-dependent dielectric permittivity of a classical perovskite relaxor, La-modified lead zirconate titanate, clearly suggest that BNT-6BT belongs to the same relaxor category, which was also confirmed by a comparative study on the temperature- dependent polarization hysteresis loops of both materials. Based on these results, we propose that the low-temperature dielectric anomaly does not involve any phase transition such as ferroelectric- to-antiferroelectric. Supported by transmission electron microscopy and X-ray diffraction experiments at ambient temperature, we propose that the commonly observed two dielectric anomalies are attributed to thermal evolution of ferroelectric polar nanoregions of R3c and P4bm symmetry, which coexist nearly throughout the entire temperature range and reversibly transform into each other with temperature.

The crystal structure of the lead-free piezoelectric ceramic (Bi1/2Na1/2TiO3)0.94–(BaTiO3)0.06 was investigated by first-principles calculations and high-resolution transmission electron microscopy (HRTEM) imaging. Structures with different A-site occupation were relaxed by total energy calculations within density functional theory and then used for simulating the corresponding HRTEM images. Simulated and experimental HRTEM images were compared and the closest match selected for structure interpretation. By combining these techniques, we have identified the Bi(Ba)/Na distribution on the A-site to be homogeneous. We exclude the possibility that regions visible in HRTEM images within one grain can be attributed to different ordering but to a slight tilting of the structure with respect to the electron beam.

The composition dependent variation of domain configuration and size in Pb(Zr1−xTix)O3 (PZT) has been investigated in a detailed transmission electron microscopy study in the range of 0.40⩽x⩽0.55. Single phase composition, Pb(Zr0.45Ti0.55)O3 and Pb(Zr0.60Ti0.40)O3, the former belonging to the tetragonal, the latter to the rhombohedral phase, feature small microdomain widths coupled with a pronounced bimodal domain distribution. Samples with compositions around the morphotropic phase boundary exhibit a decrease of bimodal distribution and an increase in microdomain width associated with nanodomain formation. The investigation of micro- and nanodomains, as well as the bimodal distribution of microdomains in undoped PZT ceramics, with respect to composition, is reported. We define nanodomains as “domains arranged within microdomains possessing a width of a few nanometers.” The strict alternation of the two orientation variants of microdomains is denoted as “bimodal domain distribution,” and is characterized ...