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The lotus seedpod-based activated carbon (LSAC) is derived from pyrolysis of lotus seedpod as biomass carbon precursor, and Co3O4 is then deposited to LSAC by oxidation-precipitation and crystallization process of Co ions from Co(NO3)2 solution. The Co3O4 particles uniformly decorate on the surface and/or the inner channels of LSAC. The optimal reflection loss (RL) value of LSAC/Co3O4-paraffin wax (PW) composite reaches −39.8 dB, and the bandwidth for RL below −10 dB and −20 dB are 10.3 and 3.0 GHz, respectively, much better than that of LSAC-PW composite for the higher magnetic loss. The addition of Co3O4 particles in LSAC-PW composite significantly enhance the RL values in various thicknesses. The channels of the LSAC and decorated Co3O4 can improve the abilities of multiple scattering, dipole polarization, interface polarization and magnetic loss. This composite provides a promising method to construct high performance absorbers by using biomass carbon to tune the dielectric properties of the ferromagnetic materials.

The investigation of inexpensive, effective, environmentally friendly next-generation energy storage devices is an urgent task due to the discontinuities of new generation energy that hinder their further widely application. Among the multitudinous explored energy storage devices, supercapacitors have been regarded as the most potential energy storage systems thanks to their distinctive features of ultralong cycling lifespan, ultrafast charge/discharge process, and high power density compared with batteries and conventional capacitors. Nevertheless, the existing defect of low energy density has always been a bottleneck problem to their long-term development and widespread applications. Meanwhile, the electrodes are the core component in supercapacitors, determining the electrochemical performance directly. Consequently, transition metal oxides were chosen as the promoting materials to design and fabricate appropriately and rationally act as supercapacitor electrodes to harvest the outstanding electrochemical performance of both high energy and power density simultaneously. Here, we summarized the recent advances in transition metal oxides with different dimensions as electrodes for high-performance supercapacitors, including zero-dimensional nanostructures (nanospheres, nanocrystals, nanoparticles), one-dimensional nanostructures (nanorods, nanowires and nanotubes), two-dimensional nanostructures (nanoflakes, nanoplatelets), three-dimensional nanostructures (spherical structure, hollow structure, flower-like structure, honeycomb structure, mesoporous structure), and the corresponding supercapacitors electrochemical performance, expecting to make a thorough inquiry of the relationship between structure and property for highlighting the route to design and synthesis high-performance transition metal oxide-based supercapacitor electrodes.

Lead-free (1-x)Ba(Ti0.8Zr0.2)O3-x(Ba0.7Ca0.3)TiO3 (BZT-BCT) possesses comparable piezoelectric constant with lead zirconate titanate (PZT), but its poor temperature electric performances stability and low Curie temperature limit its application. Here we designed composition graded BZT-BCT films with improved temperature stability of piezoelectric, ferroelectric, and dielectric performances over a wide temperature range, and the d33 reaches 21 pm/V with hysteresis loop even at 180 °C, which is far above the Curie temperature of BZT-BCT ceramic and BZT-0.5BCT film. The excellent temperature stability is ascribed to the lattice distortion and strain gradient in the grains caused by ions diffusion, and could suppress phase transition. This work could bring forward a feasible design for dielectric/piezoelectric/ferroelectric devices operating in harsh temperature environment.

In inorganic–organic perovskites, the three-dimensional arrangement of the organic group results in more subtle balance of charge, spin and space, thereby providing an attractive route toward new multiferroics. Here we report the existing of multiple ferroic orderings in inorganic–organic layered perovskites with relative strong hydrogen bond ordering of the organic chains intra plane. In addition, the inter plane in perovskite is stacking via van der Waals force. However, such magnetoelectric coupling properties for this compound have not been reported since it is difficult to characterize the properties in single crystals since most of the hybrid perovskites are usually deliquescent and unstable when exposed to air. To deal with these problems, we synthesized a (CH3NH3)2CuCl4 single crystal by using a simple evaporation technique, and demonstrated ferroelectric, magnetic and magneto-electric properties of (CH3NH3)2CuCl4. The internal hydrogen bonding of easily tunable organic unit combined with 3d transition-metal layers in such hybrid perovskites make (CH3NH3)2CuCl4 a multiferroic crystal with magnetoelectrical coupling and offer an new way to engineer multifunctional multiferroic.

In this report, we systematically studied the dielectric properties of alternately doped Ba1-xSrxTiO3 films with different Ba/Sr ratios. All species are polycrystalline with an ABO3-type structure, which exhibits growth mainly along the (110) crystal face, showing intense crystallization. Regardless of the phase of the films, either ferroelectric or paraelectric, the variation in dielectric loss is insignificant, which can be attributed to the weakening of the domain wall motion. The contribution of domain wall motion to the total losses is only approximately 6.4%, as determined by hyperbolic law calculations. In addition, a model was proposed that can well explain the pinning effect of space charge on the domain wall motion. Furthermore, the FOM value and J-V characteristics indicate that the alternately doped film still possesses good dielectric performance, even in the ferroelectric phase.

In this work, Nd2(Zr1-xSnx)3(MoO4)9 (0.02 ≤ x ≤ 0.1) (NZSM) ceramics were successfully obtained through conventional solid-state route. Phase analysis, microstructure, and properties were investigated scientifically by XRD, SEM, and network analyzer, respectively. XRD results revealed that all samples with different substitution amounts of Sn4+ formed the pure phase with R-3c space group. The permittivity was related to the polarizability and the bond of Zr2-O5, the bond of Nd-O2 possessed a positive influence on Q×f. The reduced octahedral distortion and increased bond energy made the temperature coefficient more stable. Infrared reflection spectrum results showed that the permittivity was mainly caused by the absorption of phonon oscillation. The optimum properties (er = 10.34, Q×f = 74,795 GHz, τf = -13.55 ppm/°C) were obtained when x=0.02 sintered at 750 °C.

Effective adjustment of structure and morphology is considered to be an available strategy to improve the energy storage performance of supercapacitor electrode materials. Herein, a series of hierarchical NiS/carbon hexahedrons consist of self-assembling nanoplates or nanorods were synthesized via nitrilotriacetic acid (NTA)-assisted hydrothermal strategy. This study demonstrates that the micro-morphology of the unit structure constituting the hexahedrons can be controlled by adjusting the concentration of NTA. Benefiting from synergetic effect of high void space, hierarchical assembly mode and integrated composite structure, NiS/carbon hexahedrons promote adequate exposure of abundant active sites and enhance the structural stability, donating superior energy storage performance. As expected, the optimized NiS/carbon electrode (NiS/NTA-2) exhibits superb capacitive performance, including excellent specific capacitance of 1530.4 F g-1 at 1.0 A g-1 and remarkable cycle stability with 85.6% after 5000 cycles. Employing the as-prepared NiS/NTA-2 composites as positive electrode, the hybrid supercapacitor device with spectacular capacity of maximum energy density and power density up to 35.1 Wh kg-1 and 4509.3 W kg-1 and impressive long-term stability of 87.2% retention after 5000 cycles is assembled. Moreover, a light-emitting diode (LED) is successfully illuminated for up to 12 min by two devices connected in series. Based on this strategy, high-performance energy storage devices can be further developed through utilizing the modulation effect of metal complexes to design morphology controlled electrode materials.

Two-dimensional Bi2Se3 TIs were recently found to be the most promising room-temperature topological insulators for its relatively large bulk gap, but its surface frictional response is little investigated. Here, we prepared single-crystalline Bi2Se3 nanoplates with a lateral dimension up to ~ 1 μm and a thickness of less than 200 nm via a simple polyol method, and the molecular structure and morphology were characterized in detail using different methods. The micro-frictional behavior of Bi2Se3 nanoplates with different thickness is inventively investigated with AFM technique. The atomic stick–slip friction stemming from periodic crystal lattice, and the larger friction force of thinner nanoplates is attributed to the larger adhesion force and enhanced energy dissipation. This work has, for the first time, built the link of the behavior of topological protected surface and mechanical friction behavior of Bi2Se3.

Constructing functionalized carbons decorated with transition metal oxide is an efficient way to combine the cycling stability and high specific capacitance of electrodes for electric double layer capacitors and pseudocapacitors, and the morphology is undoubtedly a key factor for the electrochemical performance. Here, three activated carbons derived from biomass with different morphologies are obtained by carbonizing rosewood (R), corncob (C) and lotus seedpod (L) waste plant body, and then the bio-activated carbons decorated with Co3O4 are prepared by simple oxidation-precipitation and crystallization method. Among the R, C, L carbons, Co3O4, R-Co3O4, C-Co3O4 and L-Co3O4 composites, the L-Co3O4 composite shows best electrochemical performance. At a scan rate of 5 mV s−1, its specific capacitance reaches 1405.3 F g−1 (975 C g−1 at 1 A g−1). Furthermore, a hybrid capacitor is fabricated using L-Co3O4 as the positive electrode and activated carbon as the negative electrode, resulting in energy density of 23.1 W h kg−1, tremendous power density of 3990.6 W kg−1 and high cycling stability (80.2% retention and coulombic efficiency of 98.8% after 5000 cycles). The equipped hybrid supercapacitor device can work for more than 10 min by lighting a red bulb. Thus, this unique L-Co3O4 composite with simple fabrication method can be considered to be a promising candidate for the electrochemical energy conversion and storage.

Self-poling has been found in many two-dimensional epitaxial ferroelectric nanofilms originating from epitaxial growth clamping and has become a new research focus due to its potential applications in designing new types of ferroelectric devices. However, self-poling ferroelectrics based on internal strain gradients rather than external stimuli still do not exist. Here, we demonstrate a novel and unique design for one-dimensional structures and geometries in microscale with robust upward flexoelectric self-poling created by the application of electrospun ferroelectric fibers on a patterned substrate to introduce curving structure arises from the uneven substrate and confinement by other fibers in space. The fiber textile composed of these curving structures could resist external electric field and temperature, and can be fabricated into high performance poling-free flexible nanogenerators with outputs comparable to the poled ones. These results are conducive to providing a potential solution to the depolarization problem, to simplifying the technologies for manufacturing piezoelectric nanogenerators by avoiding the application of electric field for poling, and to providing extra freedom in controlling ferroelectric polarization and designing new types of devices.

A series of Aurivillius-phase Bi5Ti3XO15 (X = Cu, Mn, Ni, V) (BTXO: BTCuO, BTMnO, BTNiO and BTVO) were successfully prepared using a modified micro-pulling down method and their electric and magnetic properties were carefully studied. BTVO is ferroelectric at room temperature with a diamagnetic behavior due to the absence of magnetic ions in the compound. BTCuO and BTNiO show apparent ferroelectric behavior at room temperature (RT), contrarily to BTMnO which shows negligible polarization. In terms of their magnetic properties, BTMnO is a weak ferromagnetic (canted antiferromagnetic) at temperatures below 19 K, while BTCuO and BTNiO are basically paramagnetic at low temperature and possible with a short-range magnetic ordering at RT. We do not have any evidence showing the coexistence of both ferroelectric polarization and long range magnetic ordering in any of these compounds.

Single-phase materials that combine electric polarization and magnetization are promising for applications in multifunctional sensors, information storage, spintronic devices, etc. Following the idea of a percolating network of magnetic ions (e.g., Fe) with strong superexchange interactions within a structural scaffold with a polar lattice, a solid solution thin film with perovskite structure at a morphotropic phase boundary with a high level of Fe atoms on the B site of perovskite structure is deposited to combine both ferroelectric and ferromagnetic ordering at room temperature with magnetoelectric coupling. In this work, a 0.85BiTi0.1Fe0.8Mg0.1O3–0.15CaTiO3 thin film has been deposited by pulsed laser deposition (PLD). Both the ferroelectricity and the magnetism were characterized at room temperature. Large polarization and a large piezoelectric effective coefficient d33 were obtained. Multifield coupling of the thin film has been characterized by scanning force microscopy. Ferroelectric domains and ma...

A newly discovered nanometer material-mediated piezoelectrochemical (PZEC) for the direct conversion of mechanical energy to chemical energy has attracted increasing attention, for its great potential to be a green dye water decomposition technique. However, it is far from being a cost-effective and practical technique because only ultrasonic can be scavenged to decomposed organic pollutant in previous studies. Here, we prepared 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) piezoelectric fibers for the degradation of dye solution via slow stirring and studied the degradation mechanism. It provides a practical, green and low-cost method for decomposing organic dye by scavenging waste mechanical energy from the surrounding environment.

A novel electrode material of α-NiS, β-NiS and Ni3S4 particles co-decorated rGO is obtained by co-reduction of Ni2+ and GO with thiourea. The multiple nickel sulfide phases and rGO synergistically improve the electrochemical performance of the supercapacitor electrode, which shows high specific capacity of 609.4C g−1 at current density of 1 A g−1. The electrode can keep a good stability with coulombic efficiency of as high as 99.5% after 1000 cycles. The small solution and charge transfer resistances of 0.42 and 0.24 Ω indicate the positive synergistic effects of the multiple phases of NiS and graphene on the electrochemical performance.

The domain structures and phase evolution in mixed ferroelectric (Fe): KTa 1− x Nb x O 3 (KTN) crystals were investigated. Temperature dependent Raman spectra show that Curie temperatures of KTN and Fe: KTN are far below room temperature, but the ferroelectric domain switching was still visualized by scanning probe microscopy at room temperature. These observed domains origin from the nano-regions near the grain boundaries. In addition, the intrinsic domains (triangle for KTN and straight line/stripe for Fe: KTN) could only be observed at low temperature by transmission electron microscopy. Three phase transitions in Fe: KTN crystals were found by Raman spectroscopy and dielectric testing: 175 K for Rhombohedral-to-Orthorhombic ( R – O ), 210 K for Orthorhombic-to-Tetragonal ( O – T ) and 250 K for Tetragonal-to-Cubic ( T – C ), which is consistent with the domain behavior.

MoS 2 is a promising anode material due to its graphite-like structure and high theoretical capacity (∼670 mAh g −1 ). Fast capacity fading and severe structural deterioration as a result of repeated lithium insertion restrict its application, however. Recently, we successfully synthesized a new type of MoS 2 /C composite and found that the composite showed excellent electrochemical performance, such as by its high capacity of 982 mAhg −1 after 100 cycles. The composite was synthesized by a simplified thermal reduction method in which cetyl trimethylammonium bromide (CTAB) and silica nanospheres are used as the carbon source and template material, respectively. Such favorable capacity retention could be attributed to the large specific surface area due to the effective carbon dispersion in the composite, as well as the enlargement of the interlayer spacing in the S-Mo-S structure.

0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 (0.5BZT-0.5BCT), one of the most promising lead-free piezoelectric materials invented in recent years, has not been optimized for its thin film to show best electric performance. In this work, 0.5BZT-0.5BCT thin films were fabricated via a sol-gel technique, and the effects of solvent and additive on the microstructure, morphology and dielectric, ferroelectric, and piezoelectric properties were studied. Results showed that the 2-methoxyethanol (2-MOE) solvent resulted in 0.5BZT-0.5BCT thin films with much improved microstructure and morphology in comparison with thin film from absolute ethanol solvent. Furthermore, the film becomes even denser, smoother, and more homogeneous after the monomer ethylene glycol (EG) or polyethylene glycol of 400 molecular weights (PEG400) were added into the precursor with 2-MOE as solvent. Especially, addition of PEG400 into the solvent will result in the best thin film with both less macro and micro defects and high electric performance. The 0.5BZT-0.5BCT film from 2-MOE solvent with PEG400 additive shows a high dielectric constant e up to 1756, dielectric tunability about 44%, Pr around 17.2 μC/cm2, and Ec about 39.0 kV/cm.

The brittleness of bulk ferroelectric ceramics perplexes the fabrication process for energy harvesters and reduces their durability. As one-dimensional nanostructures, ferroelectric nanofibers possess excellent performance such as decreased elastic coefficient and increased d33 with the decrease of the diameter (Ico et al., 2016; Bai et al., 2012) [1] , [2] , and can be easily deformed by tiny irregular mechanical vibration, therefore they are extremely useful in the fabrication of energy harvesters. We prepared KNNS-BNKZ nanofibers, BZT-BNT nanofibers, and PZT nanofibers with great ferroelectric performance, and fabricated energy harvesters based on these fibers then discussed the mechanism of energy harvesting, and realized energy collection and storage.

Multiferroic materials exhibit the coexistence of ferromagnetic, ferroelectric, or ferroelastic orders. Multiferroic material with cross-coupling properties at room temperature (RT) exist rarely in nature; the new design of nanoengineered thin films with strong magneto-electric (ME) coupling is both fundamentally and practically challenging. Here we present our recent advances in the Aurivillius layered multiferroics of Bi5Ti3FeO15 (BTFO15), Bi6Ti3Fe2O18 (BTFO18), Bi7Ti3Fe3O21 (BTFO21), and Bi9Ti3Fe4O27 (BTFO27). The ME coupling of ~ 400 mV/Oe·cm at RT in BTFO15 thin film has been observed, which is much higher than the previously reported value of 0.1 mVcm− 1 Oe− 1 and 8.28 mVcm− 1 Oe− 1 in the ceramic samples. Their microstructures show the strong intergrowth of the layer structure in this class of material. Scanning probe microscope measurement shows the magnetic domain switched together with the electric domain by an electric field. The disappearance of magnetic ordering evidenced by magnetization measurement therefore leads us to conclude that overall spin disordering with localized ordering is characteristic of this class of material during ME coupling. Our work could also point the way for research into novel multiferroic material in locally magnetic ordered systems.

Strain is a powerful tool for tuning the magnetic, ferroelectric, multiferroic, and superconducting properties of perovskites due to the reconstruction of spin, orbit, and charge at the film-substrate interface. In this work we demonstrate both the dynamic and static strain tuning effects on the properties of strong electron correlated perovskite oxides. The static strain tuning example used is the epitaxial pseudo cubic SmFeO3 thin film on (100) Nb-SrTiO3. High-resolution transmission electron microscope images reveal the stress-induced structural distortion at the film/substrate interface. Both rectangular ferroelectric loops and piezoelectric force microscope images at room temperature indicate the presence of ferroelectric polarization. A strong ferromagnetic-like transition was observed at 185 K. The coexistence of ferroelectric polarization and magnetic ordering reveals that the strained SmFeO3 is multiferroic. The dynamic strain tuning effect was demonstrated in a La2/3Ca1/3MnO3 film on BaTiO3 (BTO) substrate. A sharp drop in resistance and a magnetization anomaly have been observed in La2/3Ca1/3MnO3 film in the zero magnetic field at the BTO substrate structural-phase transition temperature, due to the substrate clamping/strain effect, which is confirmed by Raman scattering.

Multiferroicity has now become one of the hottest research topics in condensed matter physics and materials science. The magnetoelectric (ME) properties and coupling behavior of single-phase multiferroics are dominated by their domain structures. However, multiferroic materials exhibit very complicated domain structures. Studies on domain structure characterization and domain switching are a crucial step in the exploration of approaches to the control and manipulation of magnetic (electric) properties using an electric (magnetic) field or other means. In this chapter we summarize some of the important research activities in the recent years on domain switching in single-phase multiferroic materials in the form of single crystals and thin films, especially the domain switching behavior involving strain and the related physics. The effects of a series of stimuli such as electric field, magnetic field, and stress effects on domain switching will be shown.

Piezoelectric nanogenerators that power micro/nano devices by converting surrounding tiny mechanical vibration into electrical energy and getting rid of batteries and power cables is attracting increasing attention in recent years. Piezoelectric nanocomposites combining the flexibility of polymers and piezoelectricity of nanostructures are the current research hot spot in this field. However, usually the piezoelectric constant (d33) of piezoelectric nanostructures cannot compete with those of ceramics, and that of lead-free nanostructures is even worse, leading to low output voltages and seriously restricting their applications. Here, we report a new piezoelectric nanocomposite based on 0.96(K0.48Na0.52)(Nb0.95Sb0.05)O3–0.04Bi0.5(Na0.82K0.18)0.5ZrO3 (KNNS–BNKZ) electrospun nanofibers with a ultrahigh d33 of 338 pm V−1 and significantly improved energy harvesting performance. Our KNNS–BNKZ nanofiber-based nanogenerator can generate an output voltage up to 10 V which is more than three times that of other reported lead-free piezoelectric nanocomposites. In addition, our nanogenerator can charge a capacitor up to 0.33 μF and 8 V in 45 seconds by hand-pressing after rectifying, showing its great potential in powering micro/nano electronic devices and sensors.

We evaluated the growth and dissolution behavior of the primary α phase, Sr(NO3)2, and peritectic β phase, Sr(NO3)2·4H2O, coexisting in aqueous solutions above or below the peritectic temperature (Tp) in situ. Above Tp, when the two phases simultaneously grew in close proximity, the metastable β phase began to partially dissolve where it approached the α phase, although the remaining portion of the β phase was still growing. Overall, the growing α phase could not approach the dissolving face of the β phase; thus, a peritectic microstructure with the α phase enclosing the β phase was not formed. Conversely, below Tp, regardless of whether the metastable α phase was growing or dissolving, the stable β phase engulfed the α phase, resulting in a peritectic microstructure with the β phase enveloping the α phase. This demonstrated that it is necessary for the stable phase to dominate the metastable phase in growth kinetics for bringing about a peritectic microstructure consisting of the metastable phase in the ...

Aurivillius Bi6Ti3Fe2O18 thin films were deposited by pulsed laser deposition (PLD). X-ray diffraction patterns indicated that the obtained thin films were polycrystalline and belong to orthorhombic F2mm(42) space group. Ferroelectric measurements of as-obtained Bi6Ti3Fe2O18 thin films present an increasement of polarization with increasing substrate temperature which is result from a decrease of leakage current in the films. The positive-up-negative-down (PUND) measurements show switched and non-switched polarization in all of the Bi6Ti3Fe2O18 thin films, which manifest the ferroelectricity in as-deposited thin films. Fatigue-free behavior was obtained in Pt/Bi6Ti3Fe2O18/Pt capacitors. Piezoresponse force microscopy (PFM) measurements show out-of-plane piezoelectric response and demonstrate the ferroelectric polarizability.

Vibration-electrical energy converters for energy harvesting based on the piezoelectric effect were investigated. The unimorph of PZT with a higher Tc and Mn-doped BaTiO3-based ceramics produced greater power and energy. Two unimorphs consisting of PZT (Tc = 320°C) and Mn-0.2mol% doped BT ceramics produced 3493 mJ and 193 mJ. Thermal energy harvesting using nonlinear pyroelectric effects was investigated in PLZT ceramics with different Tc and BT-based ceramics. PLZT(9.1/65/35) ceramics exhibited energy generation of 52J/L/cycle. Adiabatic temperature change (ΔT), due to electrocaloric effects was estimated from the polarization change. ΔT of 0.015 and 0.023K were estimated for BaTiO3 and PLZT(9.1/65/35) ceramics.

Lead-free, high piezoelectric performance, Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-0.5BCT) sub-micron powders with perovskite structure were fabricated using the sol-gel process. A 0-3 type composite was obtained by choosing epoxy resin as matrix and BZT-0.5BCT, acetylene black as functional phases. Particular attention was paid to the damping behavior of composite with different content of BZT-0.5BCT powders, the influence of frequency and loading force on the damping properties were also analyzed. A mathematical model was developed to characterize the damping properties of the composites. It found that the piezoelectric effects and interfacial friction play a key role in damping behavior of composites, and a large dissipated loss factor of tanδ was found at the BZT-0.5BCT content of 20 vol %.

For practical application, the functional piezoelectric film in microelectromechanical systems should meet the requirement of physical properties, as well as the mechanical properties. In this article, 0.5Ba(Ti0.8Zr0.2)O3–0.5(Ba0.7Ca0.3)TiO3 (0.5BZT–0.5BCT) thin films with varied properties were prepared on (100) Si substrates via a sol–gel technique at different annealing temperatures. The effects of the annealing temperature on the morphology, piezoelectricity, hardness, and elastic modulus were studied. Particular attention was paid to the surface frictional behavior of films, and the changes in the friction force can be radically explained in terms of differences in the hardness/elastic modulus ratio and the residual stress of films. And, it reveals that the higher ratio of hardness to elastic modulus and tensile residual stress can contribute to a lower friction force for 0.5BZT–0.5BCT film during sling friction.

Potassium niobate crystal KNbO3 (KN) is a well-known crystal for lead free piezoelectric or nonlinear optical applications. The KN crystal has been studied in both single crystal form and in thin film form which has resulted in many review articles being published. In order to exceed the KN crystal, it is important to study KN phase forming and doping effects on the K site. This article summarizes the authors’ study towards a multiple alkali metal doped KN crystal and related single crystals briefly from the viewpoint of crystal growth.

An epitaxial pseudocubic SmFeO3 thin film on (100) Nb-SrTiO3 was studied based on ferroelectric (FE) characterization and magnetic measurements. High-resolution transmission electron microscopy images clarify the nature of the epitaxial growth, the stress-induced structural distortion at the film/substrate interface, and the existence of two different orientation lattices. Clear grain boundaries can be seen, which could introduce an extra local distortion. Rectangular FE loops can be observed at room temperature, even by just applying a small voltage ranging from -1 to +1 V, indicative of the presence of FE polarization. Piezoelectric force microscopy images confirm the existence of FE domains and the switchable polarization. A strong ferromagnetic-like transition occurs around 185 K, which is much lower than the transition observed in the bulk sample. It is believed that the pseudocubic structure enhances FE polarization and decreases the magnetic ordering temperature, which is confirmed by the first-principles theoretical calculations. Meanwhile, the ferroelectricity in this thin film should originate from distortion and modification in the structural modules rather than from the exchange striction interaction that is found in the bulk SmFeO3.

In this paper, CsLiB 6 O 10 (CLBO) crystals were grown by top-seeded solution growth (TSSG) method using self-flux. The temperature and frequency dependences of the dielectric constant, dielectric loss, AC conductivity and impedance spectroscopy for different cuts CsLiB 6 O 10 crystals were investigated, also temperature characteristics of the resonance frequency and electromechanical coupling were studied. The results show that (0 0 1)-plane of CsLiB 6 O 10 crystal has the highest dielectric constant with a value of 109, highest AC conductivity and highest electromechanical coupling factor of about 17% at elevated temperature, these make CsLiB 6 O 10 crystal excellent candidate for electrical application at elevated temperature. Also the anisotropy of electric properties has strong relationship with the crystal structure.

Some kinds of material in the environment due to the accident at the Fukushima Nuclear Power Plant have been contaminated by radioactive cesium (134Cs and 137Cs), which are represented by dehydrated sludge, surface soil and disaster wastes generated by the Great East Japan Earthquake. Treatment (transportation, temporary storage and incineration) and disposal of the contaminated materials should be carried out while ensuring the safety of radiation for the workers and the public. In this study, in order to provide the technical information for making the criteria, the dose estimation for scenarios on the treatment and disposal is conducted, based on the method used for driving the clearance levels in Japan. Minimum radioactive cesium concentration in contaminated material, that is, limiting activity concentration which is practicable for ordinary treatment and/or disposal, is calculated from the dose results, corresponding to the effective dose criteria indicated by the Nuclear Safety Commission of Japan. From the calculation result, it is suggested that it is necessary to forbid reusing the disposal site as construction, resident and agriculture in which the calculated doses for the public are higher than those in the other exposure pathways. Limiting concentration of radioactive cesium (134Cs and 137Cs) is derived to be 8,900Bq/kg for the external exposure pathway in landfill work under the condition of limited reuse of the site. In the case of the concentration below 8,900Bq/kg, the calculated dose of the resident due to direct and sky-shine radiation scattered in the air and ground from the interim storage place is less than 1mSv/y, irrespective of the distance from the storage place.

ZnO/Co multilayers with different layers have been deposited on silicate (100) substrate by the pulsed laser deposition method. The as-deposited multilayers present the structure of amorphous phase and a narrow hysteresis loop with high saturation magnetization and low coercivity, showing the typical soft magnetic behavior. The post annealing at the elevated temperature causes the transformation from as-deposited amorphous phase to crystalline metallic cobalt and ZnO phase, as well as the interdiffusion of different layer forming CoO and ZnCo 2 O 4 phases. The presence of crystalline metallic cobalt phase with ferromagnetic (FM) and cobalt oxide (CoO) phase with antiferromagnetic (AFM) is beneficial to the FM–AFM coupling, resulting in the shift of widening of the hysteresis loop. But an excessively high annealing temperatures leads to the formation of large amount of simple or complex oxides with paramagnetic, antiferromagnetic properties, inducing the decrease of magnetic properties significantly.

A state-of-the-art spherical aberration-corrected STEM was fully utilized to directly visualize the multiferroic domain structure in a hexagonal YMnO3 single crystal at atomic scale. With the aid of multivariate statistical analysis (MSA), we obtained unbiased and quantitative maps of ferroelectric domain structures with atomic resolution. Such a statistical image analysis of the transition region between opposite polarizations has confirmed atomically sharp transitions of ferroelectric polarization both in antiparallel (uncharged) and tail-to-tail 180° (charged) domain boundaries. Through the analysis, a correlated subatomic image shift of Mn-O layers with that of Y layers, exhibiting a double-arc shape of reversed curvatures, have been elucidated. The amount of image shift in Mn-O layers along the c-axis is statistically significant as small as 0.016 nm, roughly one-third of the evident image shift of 0.048 nm in Y layers. Interestingly, a careful analysis has shown that such a subatomic image shift in Mn-O layers vanishes at the tail-to-tail 180° domain boundaries. Furthermore, taking advantage of the annular bright field (ABF) imaging technique combined with MSA, the tilting of MnO5 bipyramids, the very core mechanism of multiferroicity of the material, is evaluated.

In order to search candidate multiferroics, a heterostructure of Nd:BiFeO 3 /YMnO 3 (BFO/YMO) was designed. It was fabricated using a pulsed laser deposition (PLD) method on (111) Nb: SrTiO 3 substrate through layer-by-layer growth. The particularly interesting phases for Nd:BiFeO 3 ( P 4 mm ) and YMnO 3 (hexagonal and orthorhombic) were observed. This film has a high ferromagnetic Curie temperature at 420 K. The ferroelectric domain switching was observed and it exhibited large electromechanical coupling with maximum d 33 ∼73 pm/V at 10 V.

The sensitive analysis of radionuclide migration for the scenarios on deterioration or loss of safety functions expected in HLW disposal system due to the human error (initial defective scenarios) is performed in this study. Release rates for Cs-135 and Se-79 are estimated from Monte Carlo-based analysis. Maximum release rates of Se-79 and Cs-135 from natural barrier in initial defective scenarios for vitrified waste and overpack are approximately equivalent to that in normal scenario on all safety function working. Maximum release rate of Se-79 in initial defective scenario of buffer under the condition of colloidal migration is about 30 times as high as that in normal scenario. Maximum release rate of Cs-135 in initial defective scenario of plugs is about two orders of magnitude higher than that in normal scenario. These results especially indicate the need to understand the feasibility on two types of initial defective scenario, leading to the loss of restraint for colloidal migration in buffer and the loss of restraint with plugs from short-circuit migration.

A lead-free piezoelectric material with ultra-high properties, Ba(Ti0.8Zr0.2)O3–x(Ba0.7Ca0.3)TiO3(BZT–xBCT) nanocrystals was synthesized via a sol–gel method, and the corresponding thin films were also deposited on Pt/Ti/SiO2/Si substrates by a spin-coating approach. The BZT–xBCT thin film exhibited a high remnant polarization of 22.15 μC cm−2 with a large coercive field of 68.06 kV cm−1. The resultant gel is calcined at various elevated temperatures and studied with FTIR/XRD/Raman/DSC-TGA/AFM/SEM techniques for gel composition, crystallization, phase transition, thermochemistry and the morphology of the film. Although the room temperature crystal structure of the BZT–xBCT nanocrystals appears to be a standard perovskite structure by conventional X-ray diffraction (XRD), Raman spectroscopy demonstrates the presence of non-centrosymmetric regions arising from the off-centering of the titanium (zirconium) atoms. The Raman spectra findings demonstrate the degree by which the tetragonal phase grows with the increase of calcining temperature in BZT–0.5BCT, and the characteristic ferroelectric–ferroelectric phase transition in BZT–xBCT while going through the MPB process. The structural and constituent evolution for the conversion process from gel to ceramic, as well as the formation mechanism of the BZT–0.5BCT crystallite, were also elucidated.

Cross-coupling of ordering parameters in multiferroic materials by multiple external stimuli other than electric field and magnetic field is highly desirable from both practical application and fundamental study points of view. Recently, mechanical force has attracted great attention in switching of ferroic ordering parameters via electro-elastic coupling in ferroelectric materials. In this work, mechanical force induced both polarization and magnetization switching were visualized in a polycrystalline multiferroic Bi0.9La0.1FeO3 thin film using a scanning probe microscopy system. The piezoresponse force microscopy and magnetic force microscopy responses suggest that both the ferroelectric domains and the magnetic domains in Bi0.9La0.1FeO3 film could be switched by mechanical force as well as by electric field. High tip stress applied on our thin film is demonstrated as able to induce ferroelastic switching and thus induce both ferroelectric dipole and magnetic spin flipping, as a consequence of electro-elastic coupling and magneto-electric coupling. The demonstration of mechanical force control of both the ferroelectric and the magnetic domains at room temperature provides a new freedom for manipulation of multiferroics and could result in devices with novel functionalities.

Multiferroics have received intense attention due to their great application potential in multi-state information storage devices and new types of sensors. Coupling among ferroic orders such as ferroelectricity, (anti-)ferromagnetism, ferroelasticity and so on will enable dynamic interaction between these ordering parameters. Direct visualization of such coupling behavior in single-phase multiferroic materials is highly desirable for both applications and fundamental study. Manipulation of both ferroelectric and magnetic domains of Bi5Ti3FeO15 thin film using electric field and external mechanical force is reported, which confirms the magnetoelectric coupling in Bi5Ti3FeO15, indicates the electric and magnetic orders are coupled through ferroelasticity. Due to the anisotropic relaxation of ferroelastic strain, the back-switching of out-of-plane electric domains is not as obvious as in-plane. An inevitable destabilization of the coupling between elastic and magnetic ordering happens because of the elastic strain relaxation, which result in a subsequent decay of magnetic domain switching. Mechanical force applied on the surface of Bi5Ti3FeO15 film generates by an atomic force microscopy tip will effectively drive a transition of the local ferroelastic strain state, reverse both the polarization and magnetization in a way similar to an electric field. Current work provides a framework for exploring cross-coupling among multiple orders and potential for developing novel nanoscale functional devices. The sharp tip of a scanning probe microscope has helped researchers both visualize and manipulate domains in multiferroic thin films. Bismuth-layered oxides, such as Bi5Ti3FeO15 film, may serve as next-generation memory devices because they have nanoscale structures that can be switched by applying electrical impulses. Tingting Jia from the National Institute for Materials Science in Japan and colleagues have now discovered another way to control ferroelectric and magnetic domains in Bi5Ti3FeO15 – applying a mechanical force. Direct imaging revealed that applying a vertical force to bismuth-based samples induced spontaneous ferroelastic strain forces that coupled to magnetoelastic domains in the film. These interactions enabled the team to write surface patterns with an electrified probe tip and then reverse them through probe contact – a possible mechanical solution to electrical switching problems in high-density data storage. Mechanical force applied on the surface of Bi5Ti3FeO15 film generates by an AFM tip will effectively drive a transition of the local ferroelastic strain state, reverse both the polarization and magnetization in a way similar to an electric field. Manipulation of both ferroelectric and magnetic domains of Bi5Ti3FeO15 thin film using electric field and external mechanical force is reported, which confirms the magnetoelectric coupling in Bi5Ti3FeO15, indicates the electric and magnetic orders are coupled through ferroelasticity. Current work provides a framework for exploring cross-coupling among multiple orders and potential for developing novel nanoscale functional devices.

Although potassium niobate K4Nb6O17 single crystal is easy to absorb moisture due to the intercalation of water molecules in the crystal, single crystals can be grown in fiber shape using an original pulling down method. K4Nb6O17 single crystals are easy to break down in plate shape by cleavage which is in turn affected by moisture. The dielectric constant and electric polarization measurements show that K4Nb6O17 single crystal is with weak ferroelectricity.

Alkali metal (Na, Rb or Cs) doped KNbO 3 single crystals are grown using an original pulling down method by means of co-doping with Na (small ionic size), Rb (large ionic sizes) or Cs (large ionic sizes) into KNbO 3 . Single-phase crystals are successfully grown with orthorhombic system at room temperature, for all the pure and doped KNbO 3 . Their electric properties, such as the dielectric constant and the impedance, are found to be changed according to the co-doping elements.

In order to find high-performance multiferroic materials, which are good candidates for lead-free piezoelectric/ferroelectric films, a new type of heterostructural thin film of YMnO3/SnTiO3+x (YST) was designed and produced. SnTiO3 is a metastable but promising lead-free ferroelectric material. Our expectation was that it could be stabilized by alternating YMnO3 layers. Here we report the fabrication and ferroelectric, piezoelectric and magnetic properties of YST films. Antiferromagnetic and ferroelectric properties were observed to coexist on the YST film with four layers, fabricated using the pulsed laser deposition method on (1 1 0) Nb:SrTiO3 substrates. Although some basic ferroelectric properties of the SnTiO3 films have previously been reported, further study is needed to obtain high-performance SnTiO3 films.

Double perovskite structured multiferroic Bi 2 FeMnO 6 hollow particles have been fabricated on silicon substrates from a sol-gel precursor by an electrospray method. The as-prepared Bi 2 FeMnO 6 polycrystalline samples are pure-phase, crystallizing in space group R3c . Raman spectra have verified the vibrational frequencies in the Bi 2 FeMnO 6 samples. The Bi 2 FeMnO 6 nano-/micron-sized hollow particles show a porous shell with large interior void. The shell thickness is ∼100 nm. The structure and morphology of the sample were found to be controlled by the deposition time. The formation mechanism can be explained by an Ostwald ripening − Kirkendall model. The temperature dependence of the magnetization curve ( M – T ) and magnetic hysteresis loops indicate that Bi 2 FeMnO 6 particles exhibit weak ferromagnetic moment at both low and room temperature.

Method to synthesize KNbO3 crystals using K2NbO3F solutions is of interest. In this paper, films of KNbO3 crystals are synthesized on several oxide substrates from K2NbO3F solutions. The films have some orientation due to a reaction with the substrates. The reason is expected the solution after the synthesis is strongly basic.

Alkali metal (Na, Rb or Cs) ion doped KNbO3 fiber single crystals are grown using an original pulling down method, to improve their composition change during a crystal growth, by means of co-doping of small ionic size Na and large ionic size Rb or Cs into KNbO3. In spite of the co-doping, single crystals can be grown with orthorhombic single-phase at room temperature, as well as pure KNbO3. Their electric properties, such as impedance, are changed depending on the doping ions. Na and Rb co-doped KNbO3 is promising Pb free ferroelectric and piezoelectric crystals.