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Typical relaxor behavior was observed in lead-free 0.85BaTiO3-0.15BiAlO3 solid solution, which was found to depend on the sintering temperature of the ceramics. With the sintering temperature decreased from 1350°C to 1250°C, the relaxor behavior is enhanced while the temperature of the dielectric maximum (Tm) decreases. The decrease of sintering temperature also results in an increase in the degree of deviation from the Curie-Weiss law. The frequency dependence of the temperature Tm fits well to the Vogel-Fulcher law. Ferroelectric hysteresis loops displayed at room temperature show that the remnant polarizations (Pr) decreases as the sintering temperature decreases. [ABSTRACT FROM AUTHOR]

Relaxor behavior has been found in a new solid solution between complex perovskite Ba(Zn1/3Nb2/3 )O3 (BZN) and ferroelectric PbTiO3 (PT), prepared by solid state reactions. A strong dispersion of the maximum of dielectric permittivity (ϵ') appears around the temperature of Tm, which shifts toward higher temperatures with increasing frequency. The variation of Tm with frequency follows the Vogel-Fulcher relationship. The variation of 1/ϵ' with temperature above Tm deviates from the Curie-Weiss law, but satisfies a Lorentz-type function. The relaxor behavior becomes weaker upon increasing PT-content. [ABSTRACT FROM AUTHOR]

Single crystals of the complex perovskite solid solution (1-x)Pb(Fe2/3W1/3)O3 - xPbTiO3 [(1-x)PFW - xPT], with x = 0, 0.07, 0.13, 0.27 and 0.75, have been synthesized by the high temperature solution growth using PbO as flux, and characterized by X-ray diffraction and dielectric measurements. With the increasing amount of PT, the crystal structure at room temperature changes from a pseudo-cubic (x = 0, 0.07 and 0.13) to a tetragonal phase (x ≥ 0.27). The dielectric properties of the crystals exhibit a typical relaxor behaviour for x = 0 to 0.27 with frequency-dependent peak temperature (Tm) satisfying the Vogel-Fulcher law, while the crystals with higher PT-content undergo a first-order transition at the ferroelectric Curie temperature TC. [ABSTRACT FROM AUTHOR]

Solid solution of (1− x)LaCrO3– xBiCrO3 ( x = 0, 0.10, 0.15, 0.20 and 0.25) was prepared via the citrate–nitrate combustion synthesis. Pure perovskite phase was obtained at 800 °C, a much lower synthesis temperature than that needed in the solid-state reactions. The thermodynamics of phase formation and the ceramic sintering mechanism were investigated. The substitution of Bi3+ for La3+ was found to give a separate exothermic decomposition event in the gels and the precursor did not produce a transient liquid phase while heating to 1200 °C, as was found in ceramics prepared by solid state reaction. This finding shows that the role of Bi2O3 in the sintering of the La1− x Bi x CrO3 ceramics depends on the processing method. [ABSTRACT FROM AUTHOR]

A new solid solution of (1−x)Ba(Mg13Nb23)O3−xPbTiO3(1−x)BMN−xPT has been synthesized in the form of ceramics by solid-state reactions and characterized by means of X-ray diffraction, dielectric spectroscopy, and ferroelectric measurements. A partial solid-state phase diagram of the binary system is established. It exhibits a morphotropic phase boundary region in the composition range between x0.71 and x0.74. The dielectric permittivity of BMN has been greatly enhanced by the substitution of PT. The ceramics of 0.4BMN−0.6PT show typical relaxor ferroelectric behavior with the diffuse maximum of high permittivity shifting to higher temperature with increasing frequency. With further increase of the PT content, the permittivity peaks become sharper and frequency-independent, indicating a ferroelectric phase transition, the temperature of which (TC) increases with x. Thus, the transformation from a simple dielectric, to relaxor, and to ferroelectric phase has been demonstrated in this solid solution system. [ABSTRACT FROM AUTHOR]

Recent results on dielectric spectroscopy of relaxor ferroelectrics are reviewed and analyzed in relation to the structural peculiarities and lattice dynamics. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics derived from the solid solution of (1-x)(Na0.5Bi0.5)TiO3–xBiAlO3 (NBT-BA) (x=0–0.10) have been synthesized by solid state reactions. A pure perovskite phase was formed for x≤0.08. The temperature dependence of dielectric constant indicates an increased broadness of the dielectric peak as the amount of BA increases. The large dielectric loss of NBT ceramics at low frequency and high temperature has been significantly reduced by the substitution of BA. The high coercive field is decreased and ferroelectric hysteresis loops were displayed at room temperature. The NBT-BA ceramics exhibit improved ferroelectric and piezoelectric properties compared to pure NBT ceramics, with Pr=52 μC/cm2, Ec=44 kV/cm, d33=130 pC/N, and kp=0.23 for 0.92NBT–0.08BA. [ABSTRACT FROM AUTHOR]

A lead-free solid solution between potassium sodium niobate and silver niobate, (1-x)K0.5Na0.5NbO3–xAgNbO3 (KNN-AN, with x=0–0.36), has been prepared in the form of ceramics by solid state reaction under O2 atmosphere. The crystal chemical study shows that Ag+ ion diffuses into the KNN lattices to form a solid solution of perovskite structure with x up to 0.30. The substitution of Ag+ ion for (K0.5Na0.5)+ ion results in linear decreases in the ferroelectric Curie temperature (TC), from 420 °C in KNN down to 325 °C in 0.70KNN-0.30AN, and in the tetragonal to orthorhombic phase transition temperature (TT-O), from 190 down to 150 °C. The relative density of the KNN-AN ceramics reaches 94%. The optimum piezoelectric properties are found in the ceramics of 0.82KNN-0.18AN, with a piezocoefficient d33=186 pC/N, an electromechanical coupling factor kp=42.5%, and a TC=355 °C. For the ceramics with x=0.24, the remanent polarization reaches a maximum value of Pr=20 μC/cm2, with a reduced coercive field Ec=6.4 kV/cm and a TC=340 °C. It is shown that the (1-x)KNN-xAN ceramics exhibit piezoelectric properties which are comparable or superior to the hot-pressed KNN ceramics and other KNN-based systems. In particular, the piezoelectric properties exhibit very a good thermal stability up to high temperature, which is a significant improvement from other KNN-based piezoceramics. [ABSTRACT FROM AUTHOR]

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]

Piezoresponse force microscopy (PFM) was used to investigate the domain structure of multiferroic BiFeO3-PbTiO3 single crystlas with morphotropic phase boundary (MPB) compositions. The PFM data demonstrate the piezoelectricity and the PFM domain responses under the designed experimental setup reveal the coexistence of a rhombohedral, a tetragonal, and an orthorhombic phases in the MPB crystals, which is consistent with the results of structural refinements based on X-ray diffraction data. [ABSTRACT FROM AUTHOR]

Ceramics of (1-x)BaTiO3-xBiScO3 solid solution with compositions x = 0, 0.01, 0.03, 0.05 and 0.10 were synthesized in pure perovskite phase by a solid state reaction. The dielectric and ferroelectric properties were investigated. The temperature dependence of the dielectric permittivity shows that the ferroelectric TC increases with the increasing amount of BiScO3 substitution, which was confirmed by differential scanning calorimetry (DSC). While three dielectric anomalies associated with the three structural phase transitions were clearly observed in pure BaTiO3, the two anomalies at lower temperatures were impaired by the substitutions of BiScO3 for BaTiO3. The DSC measurements reveal that the two peaks associated with the lower temperature phase transitions disappear after the BiScO3 substitution. These results demonstrate the significant effects of BiScO3 on the structural phase transitions and dielectric and ferroelectric properties of the (1-x)BaTiO3-xBiScO3 solid solution. [ABSTRACT FROM AUTHOR]

The multiferroic solid solution of (1-x)[0.9BiFeO3--0.1DyFeO3]--xPbTiO3 with compositions around the morphotropic phase boundary has been synthesized in the form of ceramics and characterized by Piezoresponse Force Microscope (PFM) and Superconducting Quantum Interference Device. Both the original local polar domain structure and the domain evolution after poling have been studied by PFM. The PFM phase imaging has revealed some interesting details of poling and domain switching process: The out-of-plane phase image shows a uniform direction of polarization along the applied electric field, while the in-plane phase image indicates two kinds of domains with antiparallel polarizations. This kind of poled domain structure is explained based on the orientations of the polarization as permitted by the rhombohedral crystal symmetry in grains of different crystallographic orientations. The magnetic properties measured within the temperature range from 1.8K to 300K reveal an interesting sequence of magnetic transitions from a weakly ferromagnetic order (WFM1) to an antiferromagnetic state (AFM), and then to another weak ferromagnetic phase (WFM2), upon cooling. A preliminary magnetic phase diagram is proposed for BDF-34PT. [ABSTRACT FROM AUTHOR]

One of the key challenges in realizing superparamagnetism in magnetic thin films lies in finding a low-energy growth way to create sufficiently small grains and magnetic domains which allow the magnetization to randomly and rapidly reverse. In this work, well-defined superparamagnetic and ferrimagnetic Fe3O4 thin films are successfully prepared using atomic layer deposition technique by finely controlling the growth condition and post-annealing process. As-grown Fe3O4 thin films exhibit a conformal surface and poly-crystalline nature with an average grain size of 7 nm, resulting in a superparamagnetic behavior with a blocking temperature of 210 K. After post-annealing in H2/Ar at 400 °C, the as-grown α-Fe2O3 sample is reduced tofe3O4 phase, exhibiting a ferrimagnetic ordering and distinct magnetic shape anisotropy. Atomic layer deposition of magnetite thin films with wellcontrolled morphology and magnetic properties provides great opportunities for integrating with other order parameters to realize magnetic nano-devices with potential applications in spintronics, electronics, and bio-applications. [ABSTRACT FROM AUTHOR]

The multiferroic (1–x)[0.9BiFeO3–0.1DyFeO3]–xPbTiO3 (BDF–xPT) solid solution with compositions around the morphotropic phase boundary (x=0.25, 0.28, 0.31, 0.34, and 0.37) has been synthesized in the form of ceramics. The phase symmetry, microstructure, ferroelectricity, piezoresponse, and ferromagnetic properties have been characterized by various techniques. It is found that, with increasing content of lead titanate from x=0.25 to x=0.37, the grain size increases and the ferroelectric property is improved. The ferroelectric performance is further enhanced by the introduction of an excess amount (2%) of TiO2 or by sintering in oxygen atmosphere, which reduces the leakage. The local polar structure is imaged by piezoresponse force microscopy. Both the outof- plane and in-plane images reveal distinct ferroelectric domain structures, with the amplitude and the average domain size decreasing with the increase of lead titanate amount. Compared with the (1–x)BiFeO3–xPbTiO3 binary solid solution of about the same concentration of PT, the magnetic properties are enhanced in BDF–xPT due to the presence of dysprosium, as demonstrated by the ferromagnetic hysteresis loops displayed at room temperature and at 10 K, but the remnant magnetization decreases with increasing PT content. The simultaneous presence of ferroelectricity and ferromagnetism entitles the BDF–xPT solid solution a room-temperature multiferroic material. [ABSTRACT FROM AUTHOR]

A new solid solution of complex perovksite structure, (1-x)PbZrO3-xPb(Mn1/2W1/2)O3 (PZxPMnW, with x=0-0.1), is prepared by solid state reaction method. Its crystal structure, dielectric properties, and antiferroelectricity are investigated. It is found that the crystal structure of the solid solution remains in the orthorhombic Pbam symmetry with x≤0.1. The induced ferroelectric polarization (PInd) is enhanced, whereas the critical field (ECr) is decreased, with increasing PMnW concentration, indicating the softening of antiferroelectricity in PZ. The Curie temperature (TC) is also decreased with the substitution of PMnW for PZ. The grain size is significantly enlarged, which could be attributed to the presence of a transient liquid phase during the sintering process. Measurements of the magnetization by means of SQUID confirm that the Mn ion exists in a high spin state with a 2+ oxidation state. The softening of antiferroelectric order and the improvement in induced polarization make the PZ-PMnW ceramics an interesting material system for such applications as energy storage devices. [ABSTRACT FROM AUTHOR]

Ferroelectric single crystals of a new lead-reduced Bi(Zn1/2Ti1/2)O3-PbZrO3-PbTiO3 (BZT-PZ-PT) ternary solid solution system have been grown for the first time by three different methods, namely high temperature solution growth (HTSG, or flux method), top-cooled solution growth (TCSG), and top-seeded solution growth (TSSG). The chemical and thermodynamic parameters, including the flux concentration, the soaking temperature and the cooling rate, have been optimized, leading to the growth of good quality BZT-PZ-PT crystals of pseudo-cubic morphology. A large size crystal of the dimensions of 2 x 2 x 0.5 cm³ has been obtained by the TSSG technique. The crystal structure is analyzed by means of X-ray powder diffraction. The highest ferroelectric Curie temperature TC of the grown crystals is found to be 320 °C by means of dielectric measurements. A remnant polarization of 32 µC/cm² is displayed with a coercive field of 15.4kV/cm. The high TC and large coercive field of the BZT-PZ-PT single crystal make this material a promising candidate for applications in high power electromechanical transducers that can operate in a wider temperature range and at high fields. [ABSTRACT FROM AUTHOR]

The solid solution of (1-x)BaTiO3–xBiScO3 was synthesized by solid state reaction and its dielectric properties were studied by impedance spectroscopy. A dielectric anomaly was found in the temperature ranges of -30–13 °C and -60–20 °C for 0.95BaTiO3–0.05BiScO3 and 0.90BaTiO3–0.10BiScO3, respectively. The frequency dependence of the anomaly exhibits dielectric relaxation satisfying the Vogel–Fulcher law, indicating relaxorlike behavior. The relaxor state in the (1-x)BaTiO3–xBiScO3 solid solution occurs after the ferroelectric phase transition upon cooling, indicating a re-entering phenomenon. Piezoresponse force microscopic studies show that the domain wall density decreases with the addition of BiScO3. The substitution of BiScO3 also results in some no-phase-contrast areas in the domain structure image, which grow with the increasing BiScO3 amount. Decent piezoelectric hysteresis loops were obtained in these areas. The correlation between the peculiar domain structure and relaxor behavior suggests that the no-phase-contrast areas are characteristics of the domain structure of the re-entering relaxor system. [ABSTRACT FROM AUTHOR]

The article discusses that Phase transition enhanced superior elasticity in freestanding single-crystalline multi-ferroic Bismuth ferrite (BiFeO3) membranes. It suggests a general fundamental mechanism for a variety of ferroic oxides to achieve high flexibility and to work as smart materials in flexible electronics.

Ferroelectrics are usually inflexible oxides that undergo brittle deformation. We synthesized freestanding single-crystalline ferroelectric barium titanate (BaTiO3) membranes with a damage-free lifting-off process. Our BaTiO3 membranes can undergo a ~180° folding during an in situ bending test, demonstrating a super-elasticity and ultraflexibility. We found that the origin of the super-elasticity was from the dynamic evolution of ferroelectric nanodomains. High stresses modulate the energy landscape markedly and allow the dipoles to rotate continuously between the a and c nanodomains. A continuous transition zone is formed to accommodate the variant strain and avoid high mismatch stress that usually causes fracture. The phenomenon should be possible in other ferroelectrics systems through domain engineering. The ultraflexible epitaxial ferroelectric membranes could enable many applications such as flexible sensors, memories, and electronic skins. [ABSTRACT FROM AUTHOR]

Pressure-induced phase transitions in single-crystal PbZr0.54Ti0.46O3 are investigated with high-pressure Raman scattering and x-ray single crystal and powder diffraction. The appearance of a Raman peak near 380cm-1 indicates a structural transition at 3 GPa. A second transition, driven by an soft optical phonon, occurs at 9GPa. A third transition occurs above 27 GPa, accompanied by a large changes in the Raman spectrum and splitting of the (pseudo-cubic) (111) and (220) diffraction lines. We identify the transitions as a monoclinic (Cm) to rhombohedral (R3m) transition at 3 GPa, followed by a rhombohedral (R3m) to rhombohedral (R-3c) transition at 9GPa, and a further symmetry-lowering transition at 27 GPa. [ABSTRACT FROM AUTHOR]

Technologically important properties of ferroic materials are determined by their intricate response to external stimuli. This response is driven by distortions of the crystal structure and/or by domain wall motion. Experimental separation of these two mechanisms is a challenging problem which has not been solved so far. Here, we apply X-ray photon correlation spectroscopy (XPCS) to extract the contribution of domain wall dynamics to the overall response. Furthermore, we show how to distinguish the dynamics related to the passing of domain walls through the periodic (Peierls) potential of the crystal lattice and through the random potential caused by lattice defects (pinning centers). The approach involves the statistical analysis of correlations between X-ray speckle patterns produced by the interference of coherent synchrotron X-rays scattered from different nanosize volumes of the crystal and identification of Poisson-type contribution to the statistics. We find such a contribution in the thermally driven response of the monoclinic phase of a ferroelectric PbZr0.55Ti0.45O3 crystal and calculate the number of domain wall jumps in the studied microvolume. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article discusses the role of machine learning in the identification of material phase transitions and determining the presence of phase boundaries using experimental data, focusing on the collective dynamics in ferroelectric relaxors. It shows a new approach to data mining of collective dynamics toward the identification of the onset of a structural phase transition in nanometer-scale volunes evaluated by atomic force microscope tip.

The voltage modulation in spin dynamics via the spin-lattice coupling (SLC) effect has been investigated in epitaxial La0.5Sr0.5MnO3/PMN-PT multiferroic heterostructures. The critical angle for the disappearance of the first exchange (FEX) spin wave has been observed around 67° experimentally and been shifted about 4° by applying an electric field (E-field). In particular, at the critical angle, the FEX spin wave can be switched "on" and "off" by voltages, showing great potential in realizing magnonic devices. Moreover, the FEX spin wave resonance shift of 187 Oe at 173K has been realized by the voltage driven SLC effect, which is a little larger than piezostrain-induced ferromagnetic resonance shift of 169 Oe. The experimental results can be well-explained by the modified Puszkarski spin wave theory. [ABSTRACT FROM AUTHOR]

In this work, multiferroic heterostructures have been prepared by in situ growing oxide magnetic films on ferroelectric single crystal substrates using atomic layer deposition (ALD). Strong interfacial mechanical coupling between the magnetic and ferroelectric phases has been created, arising from the formation of chemical bonds at the interface due to the nature of layer-by-layer self-limiting growth mechanism of the ALD technique. An enhanced magnetoelectric (ME) coupling has been achieved, which allows an electric field to robustly switch magnetic anisotropy up to 780 Oe. In addition, electrical impulse non-volatile tuning of magnetism has also been realized through partially coupled ferroelectric/ferroelastic domain switching. The ALD growth of magnetic oxide films onto ferroelectric substrates provides an effective platform for the preparation of multiferroic heterostructures at low temperatures with an improved ME coupling, demonstrating a great potential for applications in 3D spintronics, microelectronics and data storages. [ABSTRACT FROM AUTHOR]

In this work, we synthesized (Co(t)/Pt)3 multilayers and quantitatively determined thickness and temperature dependence of spin reorientation transition (SRT) and perpendicular magnetic anisotropy (PMA) using ferromagnetic resonance measurement. The critical thickness for PMA switching as well as tremendous magnetic anisotropy change up to 645 Oe once the temperature varies from 25 °C to -153 °C are demonstrated. More interestingly, a four-fold symmetry of magnetic anisotropy was found to be prominent during the SRT. By conducting magnetic simulation with involving high order energy term, we highly related this phenomenon to the strong spinorbital coupling, which is considered to be the major energy term to tip the balance between the surface anisotropy and shape anisotropy. These results provide an opportunity for better understanding the transition behaviors which is essential for PMA structure preparation and their related devices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Morphotropic phase boundary (MPB) in ferroelectric solid solutions can significantly enhance the dielectric and piezoelectric performances of the materials. Similarly, magnetic MPB has been found to exist in a few ferromagnets and is proved to be greatly beneficial to the magnetostrictive response. In this letter, we report the finding of a magnetic MPB in the multiferroic 0.66Bi1-xDyxFeO3-0.34PbTiO3 system, which overlaps the structural MPB of ferroelectric phases. A (weak) ferromagnetic state is induced at room temperature by Dy for the rhombohedral compositions with x≥0.10. Upon cooling down from room temperature, the tetragonal compositions (x≥0.05) show only one magnetic phase transition from the paramagnetic to antiferromagnetic phase, while the rhombohedral compositions exhibit a series of magnetic phase transitions from the (weak) ferromagnetic state to an antiferromagnetic order then to another weak ferromagnetic phase. A magneto-structural phase diagram has been established that reveals the presence of a magnetic MPB and a ferroelectric MPB. More significantly, the ferroelectric and magnetic MPB regions are found to overlap with each other, pointing to interesting kinds of multiferroic couplings. [ABSTRACT FROM AUTHOR]

The central challenge in realizing electronics based on strongly correlated electronic states, or 'Mottronics', lies in finding an energy efficient way to switch between the distinct collective phases with a control voltage in a reversible and reproducible manner. In this work, we demonstrate that a voltage-impulse-induced ferroelastic domain switching in the (011)-oriented 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-PT) substrates allows a robust non-volatile tuning of the metal-insulator transition in the VOx films deposited onto them. In such a VOx/PMN-PT heterostructure, the unique two-step electric polarization switching covers up to 90% of the entire poled area and contributes to a homogeneous in-plane anisotropic biaxial strain, which, in turn, enables the lattice changes and results in the suppression of metal-insulator transition in the mechanically coupled VOx films by 6 K with a resistance change up to 40% over a broad range of temperature. These findings provide a framework for realizing in situ and non-volatile tuning of strain-sensitive order parameters in strongly correlated materials, and demonstrate great potentials in delivering reconfigurable, compactable, and energy-efficient electronic devices. [ABSTRACT FROM AUTHOR]

The local structures around Nb and Pb in the prototypical relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 (PMN) were investigated by x-ray fluorescence holography. The separate atomic images of nearest Pb around Nb revealed acute and obtuse rhombohedral structures of the crystal unit cells. The Pb-Pb correlated images showed a local structure of body-center-like 2a0 × 2a0 × 2a0 superlattice, proving a rigid three-dimensional network structural model combining the two kinds of rhombohedrons. The Pb atoms in the networks are positionally stable, while the other Pb atoms are fluctuating. This superstructure and the fluctuating Pb and Nb atoms are believed to play an important role in the relaxor behavior of PMN at the atomic level. [ABSTRACT FROM AUTHOR]

PbZr1-xTixO3 (PZT) and Pb(Mg1/3Nb2/3)1-xTixO3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter. [ABSTRACT FROM AUTHOR]

The precursor dynamics of ferroelectric phase transitions in relaxor-based ferroelectric (1 - x) Pb(Zn1/3Nb2/3)O3-xPbTiO3 single crystals, with x = 0.07, 0.10, and 0.12, were investigated using inelastic light scattering from a longitudinal acoustic phonon. An acoustic anomaly in a broad temperature range, which is characteristic of relaxor ferroelectrics, was observed. We describe the anomalies in the paraelectric phase by assuming local piezoelectric coupling inside polar nanoregions, which are surrounded by a nonpolar matrix. On the basis of local piezoelectric coupling, a relaxation time τ and a dynamic characteristic length L of the order-parameter (polarization) fluctuations were determined to be in the order of 10-13s and 10-9 m, respectively. The τ and L values increase sharply upon cooling from high temperatures but more gradually below the intermediate temperature T* (=493 - 510 K). This result implies that the local polarization fluctuations grow rapidly upon cooling down to above T* and the growth rate decreases below T*. The inflexion point of this growth process in the paraelectric phase is related to the characteristic properties of relaxor-based solid solutions. [ABSTRACT FROM AUTHOR]

We combine high-pressure x-ray diffraction, high-pressure Raman scattering, and optical microscopy to investigate a series of (1-x)Pb(Mg1/3Nb2/3)03-xPbTiO3 (PMN-xPT) solid solutions (x = 0.2, 0.3, 0.33, 0.35, 0.37, 0.4) in diamond anvil cells up to 20 GPa at 300 K. The Raman spectra show a peak centered at 380 cm-1 starting above 6 GPa for all samples, in agreement with previous observations. X-ray diffraction measurements are consistent with this spectral change indicating a structural phase transition; we find that the triplet at the pseudocubic (220) Bragg peak merges into a doublet above 6 GPa. Our results indicate that the morphotropic phase boundary region (x = 0.33 - 0.37) with the presence of monoclinic symmetry persists up to 7 GPa. The pressure dependence of ferroelectric domains in PMN-0.32PT single crystals was observed using a polarizing optical microscope. The domain wall density decreases with pressure and the domains disappear at a modest pressure of 3 GPa. We propose a pressure-composition phase diagram for PMN-xPT solid solutions. [ABSTRACT FROM AUTHOR]

Piezo-/ferroelectric crystals of a new Pb(Yb1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3ternary solid solution system with the dimensions of 30 × 30 × 12 mm3have been grown by the top-seeded solution growth method for the first time. The crystal structure is analyzed by means of X-ray diffraction at various temperature. The composition of the grown crystals is found to be near the ternary morphotropic phase boundary. The Curie temperature TCreaches 205 °C. The piezoelectric coefficient d33and the longitudinal electromechanical coupling factor k33are found to be 1800 pC/N and 90%, respectively. A remanent polarization Pr of 27.8 μC/cm2is displayed with a coercive field Ecof about 7 kV/cm. These results show that the PYMNT crystals exhibit a higher TCand a larger coercive field than the binary PMN-PT piezocrystals, making this material a promising candidate for high-power electromechanical transducers that can operate in a wider temperature range. [ABSTRACT FROM AUTHOR]

The solid solution of (1−x)Ba(Sc1/2Nb1/2)O3−xPbTiO3(0 ≤ x≤ 1) has been synthesized in the perovskite structure by solid-state reaction in the form of ceramics and characterized by means of X-ray diffraction, dielectric spectroscopy, and ferroelectric measurements. A partial solid-state phase diagram (T≈ x) of the binary system is established based on the X-ray and dielectric measurement. A morphotropic phase boundary (MPB) region is found within the composition range of x= 0.61−0.65. The dielectric permittivity is enhanced greatly by increasing the PT content, reaching peak values for the MPB compositions. The ceramics of 0.42BSN-0.58PT show typical relaxor ferroelectric behavior with diffuse maxima of permittivity, which shift to higher temperatures when increasing the frequency. With further increase in PT amount, the dielectric permittivity peaks become sharper and frequency independent, indicating a ferroelectric phase transition, the Curie temperature (Tc) of which increases accordingly. The change in dielectric properties reveal the transformation from dielectric to relaxor and to ferroelectric behavior, induced by composition in the solid-solution system. [ABSTRACT FROM AUTHOR]

Ferroelectric materials, which have a reversible spontaneous polarization and generate an electric potential when subjected to a mechanical stress (piezoelectricity), have applications in nonvolatile random access memory devices and micro-electromechanical systems. For such applications, materials that remain ferroelectric up to high temperatures are desired. Bismuth aluminate has been predicted to be one such material. We present herein the first characterization of the dielectric, ferroelectric, and piezoelectric properties of the ceramic BiAlO 3synthesized by the high-pressure method. It is demonstrated that BiAlO 3is indeed a lead-free ferroelectric with a Curie temperature TC> 520 °C, a piezoelectric coefficient d33= 28 pC/N, and a room-temperature remnant polarization Pr= 9.5 μC/cm 2. Princreases with temperature, reaching 26.7 μC/cm 2at 225 °C. [ABSTRACT FROM AUTHOR]

We present an alternate version of the undergraduate laboratory experiment developed by Dixon [Am. J. Phys. 75, 1038-1046 (2007)] that is suitable for second-year students. We study the temperature variation of the capacitance of a ferroelectric ceramic derived from barium titanate, the Ba(Ti0.9Sn0.1)O3 solid solution. The ratio of tin to titanium is chosen to provide a convenient Curie temperature near 50 °C. Using careful temperature control and real-time capacitance measurements, we track the time evolution of the capacitance in response to temperature changes at 5 Hz for runs that last up to a day. At temperatures well above the Curie temperature, Tc, the capacitance relaxation is well-described by a single exponential decay. Near Tc, the relaxation is linear in the logarithm of time over more than three decades. For T>Tc, the permittivity deviates from the Curie-Weiss law and follows another phenomenological form commonly used to describe relaxor perovskite-ceramic capacitors. [ABSTRACT FROM AUTHOR]

[Pb(Mg 1/3 Nb 2/3 )O 3 ] 0.69 (PbTiO 3 ) 0.31 single crystal of composition close to the morphotropic phase boundary has been studied by dielectric spectroscopy in the frequency range of 1–1000 kHz under hydrostatic pressure ( p ) up to 0.6 GPa. At ambient pressure two successive phase transitions have been observed: the monoclinic-tetragonal transition at T 1 = 346 K and the transition from the ferroelectric tetragonal to the cubic relaxor phase at T C = 415.7 K. At elevated pressures the temperature range of the ferroelectric tetragonal phase diminished, while the relaxor phase evolved. The p-T phase diagram shows that pressure decreases linearly T 1 and T C , as well as the temperature T m of the relaxor peak, but with different slopes: dT 1 / dp = -(2.6 ± 1.6) K/GPa, dT C / dp = -(55.5 ± 0.2) K/GPa and dT m (10 kHz)/ dp = -(48.7 ± 1.0) K/GPa. [ABSTRACT FROM AUTHOR]

The coordination polymer Pb(H2O)[Au(CN)2]2 (1) was synthesized by the reaction of KAu(CN)2 and Pb(NO3)2. The structure contains 1-D chains of lead(II)-OH2 linked via Au(CN)2- moieties, generating a 2-D slab; weak aurophilic interactions of 3.506(2) and 3.4885(5) ,& occur within and between slabs. The geometry about each lead(II) is bicapped trigonal prismatic, having six N-bound cyanides at the prism vertices and waters at two of the faces. Dehydration at 175 °C yields microcrystalline Pb[Au(CN)2]2 (2), which, along with 1, was examined by 13C, 15N, 1H, and 207Pb solid-state NMR methods. Two 15N resonances are assigned to the μ2-bridging and hydrogen-bonding cyanides in 1. Upon dehydration, the 207Pb NMR spectrum becomes axially symmetric and yields a reduced shielding span, indicating higher site symmetry, while the 13C and 15N spectra reveal a single cyanide. Although no single-crystal X-ray structure of 2 could be obtained, a structure is proposed on the basis of the NMR and X-ray powder data, consisting of a lead(II) center in a distorted square-prismatic environment, with cyanides present at each corner. The birefringence of single crystals of 1 is found to be 7.0 ⊗ 10-2 at room temperature. This value is large compared to that of most optical materials and can be attributed to the anisotropy of the 2-D slabs of 1, with all CN bonds aligned in the same direction by the polarizable lead(II) center. [ABSTRACT FROM AUTHOR]

The anisotropy of polarization in a 1D copper(II)-based coordination polymer was investigated experimentally and theoretically for the first time, revealing that the origin of the ferroelectricity and its anisotropic nature are closely related to the coordination geometry of the metal ion and the packing mode of the coordination polymer. [ABSTRACT FROM AUTHOR]

The anisotropy of polarization in a 1D copper(ii)-based coordination polymer was investigated experimentally and theoretically for the first time, revealing that the origin of the ferroelectricity and its anisotropic nature are closely related to the coordination geometry of the metal ion and the packing mode of the coordination polymer. [ABSTRACT FROM AUTHOR]

Aluminum (Al3+)-doped Pb(Mg1/3Nb2/3)O3-30PbTiO3(PMN-30PT) solid solution piezo-crystals were grown by a top-seeded solution growth method. The dielectric, piezo-, and ferro-electric properties were characterized. A dispersive maximum of dielectric permittivity was found around TC= 135 °C, which does not depend on frequency. Interestingly, the rhombohedral-tetragonal phase transition, which appears at 60 °C in pure PMN-PT and thereby causes the depoling of the crystals at a relatively low temperature, has been increased to 105 °C by means of the Al3+-doping. This extends the upper limit of application temperature for electromechanical transducers up to the TC. The piezoelectric coefficient (d33) was found to be 2000 pC/N at room temperature. The longitudinal electromechanical coupling factor k33reaches 85−90%, which shows a good thermal stability upon heating up to 135 °C. The peak to peak bipolar strain was measured to be 0.25% at an electric field of up to 17 kV/cm. [ABSTRACT FROM AUTHOR]