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We present the observation of the peculiar antiferroelectric (AFE)-like behavior, characterized by the polarization-electric field (P − E) double hysteresis loops and zero remnant polarization (P r), in the ferroelectric (FE) Cr-doped YMnO 3 (YMCO) single crystals. The AFE-like behavior in YMCO is in sharp contrast with the FE P − E single loop with high P r in the undoped YMnO 3 (YMO). The topological cloverleaf domains with ferroelectricity are observed in both YMO and YMCO. It is revealed unambiguously that the AFE-like behavior in YMCO arises from the Cr-substitution induced domain pattern transition from type-II with nonzero net macroscopic polarization to type-I with zero net polarization, as well as the recoverable type-I domain pattern after electric field sweeping. In addition, it is found that both the recoverable energy density and energy storage efficiency are significantly enhanced due to the AFE-like behavior in YMCO compared to YMO. Our results suggest for the first time that, in addition to the mechanism of the antiparallel arrangement of adjacent electric dipoles, the AFE-like behavior can be also achieved by domain engineering in a FE, which provides a possible new strategy to obtain high energy storage performance. [ABSTRACT FROM AUTHOR]

Abstract The structural, magnetic and ferroelectric properties of the Mn-doped chromites YCr 1- x Mn x O 3 (YCMO) (0.39 ≤ x ≤ 0.73) single crystals have been studied. Powder X-ray diffraction results showed an orthorhombic structure for all the samples. Detailed magnetic studies demonstrated strong ferromagnetic (FM) behavior at low temperatures in all the YCMO crystals, which is found to be due to the FM Cr3+–O2-–Mn3+ magnetic interaction. The multiferroic behavior with magnetoelectric coupling was also observed in YCMO. The electric polarization in YCMO can be attributed to the Jahn-Teller distortion instead of magnetic origin. Highlights • Low temperature ferromagnetism was observed in YCr 1- x Mn x O 3 (0.39 ≤ x ≤ 0.73) crystals. • YCr 1- x Mn x O 3 show multiferroic behavior with strong magnetoelectric coupling. • Electric polarization in YCr 1- x Mn x O 3 are ascribed to the Jahn-Teller effect. [ABSTRACT FROM AUTHOR]

Highlights: [•] Multiple temperature-induced magnetization reversals were observed in x =0.1. [•] Coexistence of normal and inverse magnetocaloric effects was observed. [•] A reasonable model was proposed to explain the magnetization reversals. [Copyright &y& Elsevier]

Abstract: We have synthesized a series of layered cobaltite Bi2Sr2−x Ca x Co2O y (0≤x≤0.3). Reduced resistivity was observed with x≤0.2 due to the possible chemical pressure induced charge transfer between the Bi2Sr2O4 layer and CoO2 layer. Enhanced thermoelectric power S was also observed in the Ca-doped samples with the largest S as for x=0.2. The variation of S(T) could reflect the change of electronic correlation or the modification of local density of states and band structure near the Fermi energy. In addition, magnetic measurements show that the samples with x=0.0 exhibit abnormal and abrupt changes, revealing a possible thermally excited spin-state transition. It is found that the thermoelectric performance is obviously enhanced by the low Ca-doping. [Copyright &y& Elsevier]

Abstract: Single-phase Bi0.85La0.15FeO3 ceramics were synthesized under various magnetic fields (H a=0T, 3T, 5T). Substantially reduced leakage current and hence modified ferroelectric (FE) properties were obtained with magnetic field annealing (MA). The largest magnetization and lowest leakage current with large FE polarization (P r∼33μC/cm2) were found in the sample annealed with H a=3T. Great changes were also observed in the Raman spectra. All the observed features originate mainly from the different FE domain wall structures induced by MA. These results demonstrate that MA is an effective way to tune the multiferroic and magnetoelectric properties in BiFeO3-based materials. [Copyright &y& Elsevier]

Abstract: Layered misfit cobaltite Bi2Ca2.4Co2O y has been synthesized by a sol–gel method. This compound exhibits large thermoelectric (TE) power (S 300K∼170μVK−1), low resistivity (ρ 300K∼42mΩcm) and relatively small thermal conductivity (κ 300K∼2.8WK−1 m−1) at room temperature. Furthermore, the resistivity of this compound displays a metallic behavior above T ⁎∼150K with a semiconducting behavior below this temperature. This abnormal behavior in resistivity is analogous to those observed in Sr and Ba based misfit cobaltites. The observed features of the TE have been discussed based on the narrow band model. [Copyright &y& Elsevier]

Abstract: Mn-substituted Bi0.8Ca0.2FeO3 ceramics Bi0.8Ca0.2Fe1−x Mn x O3 (0≤ x ≤0.5) were synthesized by a solid-state reaction method. Powder X-ray diffraction investigations performed at room temperature show that the crystal structure is rhombohedral for x ≤0.1 and orthorhombic for 0.2≤ x ≤0.5. Compared to the undoped Bi0.8Ca0.2FeO3 compound, enhanced magnetization and electric polarization were observed in the samples with x ≤0.1. A further increase in the magnetization with increasing x took place in the samples with 0.2≤ x ≤0.5. All the Mn-substituted samples studied are basically antiferromagnetic accompanied by the appearance of weak ferromagnetism, which is similar to the BiFeO3 compound. The conductivity of the samples with x ≥0.3, measured between 140 and 380K, is of the semiconducting type. [Copyright &y& Elsevier]

Abstract: Y Fe0.5Cr0.5O3 ceramics have been synthesized by a conventional solid-state reaction. Powder X-ray diffraction shows that this compound possesses an orthorhombic structure with Pnma space group. It exhibits a high magnetic transition temperature at around 250 K with weak ferromagnetic behavior below this temperature. A dielectric relaxation following the Arrhenius law found in the Y Fe0.5Cr0.5O3 compound can be attributed to the charge carrier hopping conduction. [Copyright &y& Elsevier]

High-performance and high-temperature piezoelectrics play a vital role in various applications. A major challenge, however, is how to improve their electric properties to meet the applications that demand sensitivity and reliability. Here, CaBi 2 Nb 2 O 9 textured ceramics with F 00 l ∼ 40%–70% were synthesized only through the conventional solid-state technique with the addition of CuO sintering aid. The rather excellent electrical properties with piezoelectric response d 33 of 20.6-24.9 pC/N, remanent polarization P r of 21.3-22.9 μ C/cm2, and ultra-high ferroelectric Curie temperature T C of 950-960 °C can be simultaneously achieved. Our results reveal that adding CuO sintering aid can induce strong texture and enhance lattice distortion, and makes domains miniaturization and diversification. The adjustment of microstructural and domain configuration gives rise to enhance the electrical properties of CaBi 2 Nb 2 O 9. This simple textured approach is expected to be widely applicable for the development of high-performance and high-temperature piezoelectric ceramics. • CBNO textured ceramics ( F 00 l ∼ 40–70%) were prepared by the solid-state technique. • P r in CBNO-based piezoceramics is 3–10 times as large as previous reported. • High d 3 3 and T C superior to most bismuth layered-structure ceramics. • Lattice distortion and grain orientation give rise to improve electrical properties. • Adding CuO sintering aid can make domains miniaturization and diversification. [ABSTRACT FROM AUTHOR]

Abstract: A colorimetric method for detection of DNA damage was developed by using hemin-graphene nanosheets (H-GNs). H-GNs were skillfully synthesized by adsorping of hemin on graphene through π–π interactions. The as-prepared H-GNs possessed both the ability of graphene to differentiate the damage DNA from intact DNA and the catalytic action of hemin. The damaged DNA made H-GNs coagulated to different degrees from the intact DNA because there were different amount of negative charge exposed on their surface, which made a great impact on the solubility of H-GNs. As a result, the corresponding centrifugal supernatant of H-GNs solution showed different color in the presence of 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2, which could be discriminated by naked eyes or by ultraviolet (UV)–visible spectrometer. Based on this, the damaged effects of styrene oxide (SO), NaAsO2 and UV radiation on DNA were studied. Results showed that SO exerted most serious damage effect on DNA although all of them damaged DNA seriously. The new method for detection of DNA damage showed good prospect in the evaluation of genotoxicity of new compounds, the maximum limit of pesticide residue, food additives, and so on, which is important in the fields of food science, pharmaceutical science and pesticide science. [Copyright &y& Elsevier]

Abstract: Detailed magnetic properties of polycrystalline Bi0.3Ca0.7Mn0.75Cr0.25O3 are investigated. It is observed that this compound exhibits negative magnetization below the compensation temperature (T comp) when magnetization–temperature (M–T) curves are measured in a field-cooled mode with low applied fields (H <1030Oe). Furthermore, the compound shows a canted-antiferromagnetic transition at 120K and a peak with positive sign at 98K. Below 98K, M decreases with decreasing temperature, passes through a zero value (M =0) around T comp =78.5K, and continues to decrease steeply until 5K. The maximum absolute value of M below T comp was about 15 times as large as that above T comp. Considering the fact that the observed behavior is similar to that in GdCrO3, the phenomenon of the magnetization reversal in the Cr-doped manganite Bi0.3Ca0.7Mn0.75Cr0.25O3 is suggested to originate from the antiparallel coupling of the Cr3+ moments and the canted Mn3+/4+ moments. [Copyright &y& Elsevier]

Abstract: The microstructural characteristics, mechanical properties, and cytocompatibility of ZrC films deposited on electropolished NiTi shape memory alloy (SMA) by magnetron sputtering are investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), nanoindentation, and MTT test. The deposition rate of the ZrC film is smaller than the pure Zr film. Although ZrC is the only phase in the film, the pure ZrC film with small oxygen content is non-stoichiometric. The hardness and modulus increase initially with larger nanoindentation depths, reach maximum values, and then gradually decrease afterwards as a result of the composite effects of the ZrC film and NiTi substrate. Deposition of the ZrC film promotes proliferation of fibroblasts revealing enhanced cytocompatibility compared to uncoated NiTi. [ABSTRACT FROM AUTHOR]

Abstract: ZrN is deposited on electropolished NiTi shape memory alloy to enhance the surface properties. The microstructure, mechanical properties, and blood compatibility are evaluated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), nanoindentation, hemolysis analysis, and blood platelet adhesion test. The ZrN film has a fine fibrous structure composed of the desirable stable ZrN phase together with a small amount of a second ZrO2 phase. The hardness and modulus values increase initially with larger nanoindentation depths and after reaching maximum values, gradually decrease finally attaining stable values of about 3.4GPa and 68GPa, respectively which reflect the composite hardness and modulus values of the system. Our study reveals that the ZrN film may degrade the surface wettability, but the hemolysis resistance and thromboresistance can be improved thereby making the surface treated materials more suitable in biomedical implants. [Copyright &y& Elsevier]

Abstract: Biomimetic deposition process of an apatite coating on NiTi shape memory alloy (SMA) after it was pretreated with 30% H2O2 solution and subsequently 1 M NaOH solution was studied using a simulated body fluid (SBF) soaking test. Biomimetic nucleation of apatite on the chemically pretreated NiTi SMA has a short induction period down to 6 h. With longer soaking time, more apatite appeared on the NiTi substrate but our control experiments did not reveal any apatite formation on the chemically polished NiTi SMA. After immersion in SBF for 48 h, the chemically pretreated NiTi SMA was fully covered with a dense hydroxyapatite coating. The biomimetic deposition of the apatite coating was attributed to the catalytic effect of abundant Ti–OH groups and Na2TiO3 on the surface of the chemically pretreated NiTi SMA. [Copyright &y& Elsevier]

Abstract: Effects of anodic oxidation in H2SO4 electrolyte on the biocompatibility of NiTi shape memory alloy (SMA) were investigated by characterizing surface structure, blood compatibility, wettability, release of harmful Ni ions of anodized NiTi SMA. Although titania film resulting from anodic oxidation in H2SO4 electrolyte has a porous structure, it can effectively block out-diffusion of Ni from NiTi SMA to simulated body fluid (SBF). Comparing with chemical polishing, anodic oxidation in H2SO4 electrolyte can also improve the wettability, blood compatibility, thromboresistance of NiTi SMA. [Copyright &y& Elsevier]

Abstract The structural, magnetic, ferroelectric and electrical properties of a series of (1- x)BiFeO 3 - x Ba 0.5 Sr 0.5 MnO 3 (0 ≤ x ≤ 1) solid solutions have been studied. The crystal structure of these samples changes from rhombohedral R 3 c (0 ≤ x ≤ 0.1) to cubic Pm 3 ¯ m (0.16 ≤ x ≤ 0.5) and finally to hexagonal P 6 3 / mmc (0.7 ≤ x ≤ 1.0) with increasing x. Two local maxima in the remnant magnetization M r and coercive field H c are observed in the vicinity of the two structural phase boundaries, i.e., x = 0.16 and 0.7. The samples with x ≤ 0.1 exhibit multiferroicity with magnetoelectric effect, while the samples with x ≥ 0.16 possessing centrosymmetric crystal structure show semiconducting behavior. The existence of low-valence Mn3+ ions associated with oxygen vacancies is found to influence significantly the structure, magnetism and ferroelectricity in these samples. Highlights • The two structural transitions with increasing x are rhombohedral→cubic→hexagonal. • Maximum magnetization appears at structural phase boundaries, i.e., x = 0.16 and 0.7. • The samples with x ≤ 0.1 exhibit multiferroicity with magnetoelectric effect. • The magnetodielectric effect for x = 0.05 and 0.1 are ∼0.06% and 0.1%, respectively. • The low-valence Mn3+ ions affects significantly the structure and multiferroicity. [ABSTRACT FROM AUTHOR]

Chemical substitution is an effective method for tailoring the electrical and magnetic properties of functional materials. In this work, (1–x)Ba 0.1 Sr 0.9 TiO 3 - xBiFeO 3 (0.2  ≤ x  ≤ 0.8) ceramics were prepared by the modified Pechini method. X-ray diffraction patterns manifest that the samples undergo a gradual structural transformation from rhombohedral phase to tetragonal phase with increasing the content of Ba 0.1 Sr 0.9 TiO 3 (BST). Dielectric properties show that T C can be modulated by the doping level of BST in a wide range from 885 K to 260 K accompanied by the ferroelectric transformation from non-relaxor type to relaxor type ferroelectricity. The room temperature ferroelectricity, ferromagnetism and intrinsic magnetodielectric are observed in the BiFeO 3 -rich samples. Magnetization and magnetodielectric measurement both show that the spin cycloid is destroyed by the substitution of BST and the critical field for the transition from spiral to antiferromagnetic collinear magnetic structure decreases with increasing the amount of BST. These findings manifest that this materials are quite promising for potential applications in BFO-based magnetoelectric devices and electrocaloric cooling technologies. [ABSTRACT FROM AUTHOR]

The effects of Co doping on structural, dielectric, and magnetic properties of multiferroic 0.6BiFe 1- x Co x O 3 -0.4(Bi 0.5 K 0.5 )TiO 3 (0 ≤ x ≤ 0.2) ceramics have been investigated. The samples undergo a structural transition from pseudocubic to rhombohedral phase at x = 0.1. The maximum remnant polarization of 57.8 μC/cm 2 and remnant magnetization of 0.107 emu/g are observed in the x = 0.15 sample. The ferromagnetism is proposed to originate from the suppression of spiral spin structure with the canting of the antiferromagnetically ordered spins caused by the substitution of Co for Fe ions. Moreover, the magnetodielectric effect can be observed in the x = 0.15 sample. [ABSTRACT FROM AUTHOR]

In this work we present a detailed magnetization, electron spin resonance (ESR) and specific capacity study on spinel MnCr 2 O 4 single crystals in an extended temperature range of 5–300 K. The field-induced effect of the magnetization indicates the strong spin-lattice coupling in MnCr 2 O 4 single crystal. The following results are obtained by the ESR investigation: (i) Below 35 K, since the spiral spin order, a driving force of the multiferroic (MF) effect, becomes obvious, the line shape of ESR shows asymmetric characters and the ferromagnetic resonance (FMR) model of Smit and Beljers formulation is invalid; (ii) The temperature dependence of Gilbert damping parameter α , reflecting the strength of the spin-lattice coupling, shows an abnormal behavior due to the local lattice distortion in MnCr 2 O 4 single crystal. And the distortion is a triggering force for the formation of spiral spin order. Moreover, our research helps to understand the origin of the MF effect in MnCr 2 O 4 . [ABSTRACT FROM AUTHOR]

We investigate the structural, magnetic, ferroelectric, and dielectric properties of Bi 6 Fe 2− x Ni x Ti 3 O 18 (0≤ x ≤1). The coexistence of ferroelectricity and ferromagnetism were observed at room temperature for the Ni-doped samples. The ferromagnetism in Bi 6 Fe 2− x Ni x Ti 3 O 18 can be understood in terms of spin canting of the antiferromagnetic coupling of the Fe-based and Ni-based sublattices via Dzyaloshinsky-Moriya interaction. Moreover, the substitution of Ni for Fe was effective for the enhancement of ferroelectric properties. The x =0.6 sample exhibits a maximum remnant polarization P r of 37.8 μC/cm 2 because of a lower leakage current. The rather large activation energy in the x =0 and 0.2 samples implies that the relaxation process may be not associated with the thermal motion of oxygen vacancies inside the bulk. [ABSTRACT FROM AUTHOR]

Abstract: The surface structure and biomedical properties of NiTi shape memory alloy (SMA) samples after undergoing electropolishing and chemical polishing are determined and compared employing scanning electron microscopy, X-ray photoelectron spectroscopy, inductively-coupled plasma mass spectrometry, hemolysis analysis, blood platelet adhesion test, and MTT test. The results indicate that after chemical polishing, there is still a high Ni concentration on the surface of the NiTi SMA. On the other hand, electropolishing can form a thin surface titanium oxide film (about 10 nm thickness) with depleted Ni. In addition to the TiO2 phase, some titanium suboxides (TiO and Ti2O3) are found in the surface film. Compared to chemical polishing, electropolishing can more effectively mitigate out-diffusion of Ni ions and the wettability, blood compatibility, and thromboresistance are also better. However, no difference on the cytocompatibility can be observed from samples that have been chemically polished or electropolished. [Copyright &y& Elsevier]