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SmFeO3 has received the increasing scientific attention as a promising room‐temperature single‐phase multiferroic material with great application potential in the next‐generation spintronic devices. However, the ferroelectricity of SmFeO3 has remained as a controversial issue. In the present work, high resistivity incipient ferroelectric CaTiO3 was introduced as a charge blocking layer on an SmFeO3 thin film to suppress the leakage current. CaTiO3/SmFeO3/Nb–SrTiO3 (1 0 0) thin films were prepared by a PLD (pulsed laser deposition) process, and the epitaxial growth of thin films was confirmed by XRD (X‐ray diffraction) and HRTEM (high resolution transmission electron microscope) images. The interface strain resulted in the polar non‐centrosymmetry in space group P42/mc for SmFeO3, and subsequently the room‐temperature ferroelectricity was achieved with a robust remanent polarization of about 4.9 μC/cm2. The 180° switchable domain structure was confirmed by PFM (piezoelectric force microscope). Meanwhile, strong magnetoelectric coupling with magnetoelectric coefficient (αME) of about 2.5 V/(cm Oe) was observed. The present work has revealed the structural origin of ferroelectricity in an SmFeO3 thin film and provided the great reference for its room temperature multiferroic applications. [ABSTRACT FROM AUTHOR]

Transition-metal oxides have attracted much attention due to its abundant crystalline phases and intriguing physical properties. However, some of these compounds are difficult to be fabricated directly in film form due to the ease of valence variation of transition-metal elements. In this work, we reveal the reversible structural transition between SrVO3 and Sr2V2O7 films via thermal treatment in oxygen atmosphere or in vacuum. Based on this, Sr2V2O7 epitaxial films are successfully synthesized and studied. Property characterizations show that the semitransparent and metallic SrVO3 could reversibly switch into transparent and insulating Sr2V2O7, implying potential applications in controllable electronic and optical devices. [ABSTRACT FROM AUTHOR]

The doping of ZnO is efficient to improve the piezoelectric property and thermal stability of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) based ceramics. However, the underlying physics, especially the local domain structures of the ZnO modified PMN–PT ceramics, which is strongly associated with the electric properties, is not clear yet. In this paper, we investigated the local domain structures and their evolution as a function of x in PMN–0.32PT:xZnO ceramics. It was found that, the domain evolution is mainly caused by the growth of grain size induced by the sintering aiding effect of ZnO at x < 0.04, and the domain evolution can be attributed to the phase transition induced by the partial replacement of Mg2+ by Zn2+ in the B‐site of PMN–PT lattice at x > 0.06. Furthermore, we also investigated the domain structure evolution as functions of temperature and local external electric field in PMN–0.32PT:0.06ZnO ceramics, which exhibited superior piezoelectric property relative to other compositions. We found that the irregular nanodomains are more stable at high‐temperature range, and the regular non‐180° domains exhibited more complex rotation behavior under local electric field, which probably leads to the thermal stability and piezoelectric property enhancement in the ZnO‐modified PMN–0.32PT ceramics. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction is one of the key processes in the promising renewable energy technique of electrocatalytic water splitting. Developing high efficient oxygen evolution reaction (OER) catalysts requires determination of the optimal values of the descriptor parameters. Using spinel CoFe2O4 as the model catalyst, this work demonstrates that irradiation with pulsed UV laser can control the quantity of surface oxygen vacancy and thus modify the OER activity, in a volcano-shape evolution trend. This strategy sheds light on quantitatively investigation of the relationship between surface cation valence, anion vacancy, and physicochemical properties of transition-metal-based compounds. [ABSTRACT FROM AUTHOR]

Theoretical calculations based on a multiscale model are proposed to interpret the dielectric anomalous enhancement observed around x = 0.2 in the (PbTiO3)1−x-(CoFe2O4)x (0 ≤ x ≤ 1) epitaxial nanocomposite spread film. First principles calculation combined with thermodynamics statistics reveals that the dynamic ratio between different PbTiO3 phases under an external electric field is responsible for the dielectric anomaly. To verify this model with direct microstructure evidence, high resolution and high accuracy synchrotron radiation x-ray diffraction of (PbTiO3)0.8-(CoFe2O4)0.2 epitaxial composite film under an in situ electric field is collected, in which an obvious modulation of the phase balance of PbTiO3 is observed. [ABSTRACT FROM AUTHOR]

Abstract: Composite multiferroics usually show larger magnetoelectric effect, which is important for actual application, than their single-phase counterparts. Here, (1−x)BiFeO3–xCoFe2O4 and (1−x)Bi0.8La0.2FeO3–xCoFe2O4 (, 0.2, and 0.3) multiferroic composite ceramics were prepared. The former system shows low resistivity, which prevents the intrinsic ferroelectric measurements, whereas for the later system, the composition with shows well saturated polarization–electric field hysteresis loop at room temperature, the measured remnant polarization is 13.4 μC/cm2. However, for the compositions with and 0.3, the measured loops show negative curvature near saturation, which is attributed to the decreased resistivity. Further magnetic measurements reveal that at low temperature, 0.9Bi0.8La0.2FeO3−0.1CoFe2O4 shows ferromagnetic nature whereas at high temperature antiferroelectric-like nature, which is discussed based on comparing its magnetic response with that of pure Bi0.8La0.2FeO3 and CoFe2O4 ceramics. These results may be helpful for further understanding, and designing, new multiferroic composites. [Copyright &y& Elsevier]

The hexagonal rare earth ferrites h -RFeO 3 (R = rare earth element) have been recognized as promising candidates for a room-temperature multiferroic system, and the primary issue for these materials is how to get a stable hexagonal structure since the centrosymmetric orthorhombic structure is generally stable for most RFeO 3 at room-temperature, while the hexagonal phase is only stable under some strict conditions. In the present work, h -Lu 1- x In x FeO 3 ( x = 0-1) thin films were prepared on a Nb-SrTiO 3 (111) single-crystal substrate by a pulsed laser deposition (PLD) process, and the multiferroic characterization was performed at room temperature. With the combined effects of chemical pressure and epitaxial strain, the stable hexagonal structure was achieved in a wide composition range ( x = 0.5-0.7), and the results of XRD (X-ray diffraction) and SAED (selected area electron diffraction) indicate the super-cell match relations between the h -Lu 0.3 In 0.7 FeO 3 thin film and substrate. The saturated P - E hysteresis loop was obtained at room temperature with a remanent polarization of about 4.3 μC/cm 2 , and polarization switching was also confirmed by PFM measurement. Furthermore, a strong magnetoelectric coupling with a linear magnetoelectric coefficient of 1.9 V/cm Oe was determined, which was about three orders of magnitude larger than that of h -RFeO 3 ceramics. The present results indicate that the h -Lu 1- x In x FeO 3 thin films are expected to have great application potential for magnetoelectric memory and detection devices.

Thin films of 0.85BiFe 1-2x Ti x Mg x O 3 -0.15CaTiO 3 (x = 0.1 and 0.2, abbreviated to C-1 and C-2, respectively) have been fabricated on (001) SrTiO 3 substrate with and without a conductive La 0.7 Sr 0.3 MnO 3 buffer layer. The X-ray θ-2θ and ϕ scans, atomic force microscopy, and cross-sectional transmission electron microscopy confirm the (001) epitaxial nature of the thin films with very high growth quality. Both the C-1 and C-2 thin films show well-shaped magnetization-magnetic field hysteresis at room temperature, with enhanced switchable magnetization values of 145.3 and 42.5 emu/cm 3 , respectively. The polarization-electric loops and piezoresponse force microscopy measurements confirm the room-temperature ferroelectric nature of both films. However, the C-1 films illustrate a relatively weak ferroelectric behavior and the poled states are easy to relax, whereas the C-2 films show a relatively better ferroelectric behavior with stable poled states. More interestingly, the room-temperature thermal conductivity of C-1 and C-2 films are measured to be 1.10 and 0.77 W/(m·K), respectively. These self-consistent multiferroic properties and thermal conductivities are discussed by considering the composition-dependent content and migration of Fe-induced electrons and/or charged point defects. This study not only provides multifunctional materials with excellent room-temperature magnetic, ferroelectric, and thermal conductivity properties but may also stimulate further work to develop BiFeO 3 -based materials with unusual multifunctional properties.

A parallel solution combustion synthesis technique was developed for combinatorial materials studies. The vigorous combustion reactions were successfully limited in the microreactors by using a substrate-net-mask microreactor system and the lowest adoptable furnace temperature. Using this technique, a luminescent materials library of Y3Al5O12/Tb(chi) was synthesized with the aid of an ink-jet delivery system. Structure and luminescence characterizations were implemented using X-ray diffraction and UV/X-ray spectroscopies, respectively. The results show that this technique is reliable and applicable to combinatorial study of powder materials with high synthesis temperature.