Sm-substituted barium bismuth titanate BaBi4−xSmxTi4O15 (BBSTx, x=0, 0.4, 0.6, 0.8) ceramics were prepared by a solid-state reaction method. X-ray diffraction patterns showed that the ceramics have a tetragonal structure with space group of I4/mmm at room temperature. The plate-like morphology was observed by scanning electron microscope (SEM) and the average grain size decreases with the increase of Sm substitution. The dielectric, ferroelectric properties and complex impedance spectra of BaBi4−xSmxTi4O15 ceramics were studied. The results showed that Sm substitution decreased the temperature of the dielectric maximum (Tm) obviously from 390 °C to 241 °C. A modified Curie–Weiss law was used to describe the relaxor behavior of the ceramics. Through Arrhenius fitting, the activation energy was estimated to be 0.97–1.18 eV, which could be attributed to the thermal motion of oxygen vacancies. The remnant polarization (Pr) first increases, then decreases with increasing Sm substitution, and the maximum Pr was found to be 0.60 μC/cm2 for BBST0.6 ceramics.

•Polycrystalline Bi4Ti3O12 film was deposited by a sol-gel technique.•The photovoltaic response of the devices strongly depends on the excitation light sources and top electrodes.•Time dependence of the zero bias photocurrent density indicates a repeatable photocurrent.•The photovoltaic response was explained combining Schottky barrier with surface plasmon effect.Polycrystalline Bi4Ti3O12 (BTO) film was deposited by a sol-gel method. Piezoelectric force microscopy measurement confirmed the local ferroelectricity of the BTO film. The band gap of the BTO film is estimated to be 3.45 eV and the absorption intensity of Ag/BTO/FTO is larger than that of Pt/BTO/FTO. The photovoltaic (PV) properties of the two structures were measured under the illumination of white light and purple light of 405 nm, respectively. It was found that the PV responses of the devices strongly depended on the excitation light sources and top electrodes. The devices show large ON/OFF photocurrent ratio with good stability and repeatability. The PV responses are briefly explained combined with Schottky barrier and surface plasmon effect.

•Bi4Ti3O12/BiFeO3 bilayer film was deposited on FTO substrate by a sol–gel technique.•An obviously improved photovoltaic response for the bilayer film was observed.•Time dependence of the zero bias photocurrent density indicates a repeatable photocurrent.•A model combined p–n heterostructure with ferroelectric polarization was proposed.Bi4Ti3O12/BiFeO3 (BTO/BFO) heterostructure bilayer film is prepared on fluorine-doped tin oxide conductive glass by a sol–gel process. The X-ray diffraction result shows that no additional phase can be found besides the characteristic diffraction peaks of BTO and BFO. Piezoelectric force microscopy measurement confirms the complete domain switching and local ferroelectric nature. The open circuit voltage and short circuit current density of the bilayer film are measured to be about 0.38 V and −56.24 µA cm−2, respectively, higher than those of the BTO. The BTO/BFO film exhibits repeatable and stable instantaneous response of photocurrent. A theoretical band diagram model combining p–n heterostructure with ferroelectric polarization is constructed to describe the mechanism of photovoltaic enhancement of the film.

•Pt/BiFeO3/La0.7Sr0.3MnO3 photovoltaic devices were integrated on PMN-PT single crystals.•The piezoelectric strain of PMN-PT enhances the power conversion efficiency of the devices.•The dynamic strain engineering is an unique approach for enhancing power conversion efficiency.BiFeO3 (BFO) is a unique multiferroic material that shows interesting but rather weak photovoltaic effect. Here, we report the integration of Pt/BFO/La0.7Sr0.3MnO3(LSMO) photovoltaic devices on piezoelectric 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 (PMN–PT) single-crystal substrates and realized a piezo-photovoltaic effects in the BFO/LSMO/PMN–PT heterostructures through in situ dynamical strain engineering. Upon the application of an electric field of +10 kV/cm, an in-plane compressive strain was induced in the PMN–PT via the converse piezoelectric effect, which was effectively transferred to the BFO film through the LSMO, leading to a change in the in-plane strain and bandgap of the BFO film by ~0.12% and ~22 meV, respectively. As a result, the power conversion coefficiency (PCE) η was dramatically enhanced by ~218%, corresponding to a gauge factor (Δη/η)/δεxx~1817. The results demonstrate that the dynamic strain engineering of photovoltaic properties using the converse piezoelectric effect is an effective and unique approach for realizing enhanced PCE of ferroelectric thin film-based photovoltaic devices.

Fe-doped SiC nanowires samples were fabricated using high-purity carbon nanotubes, SiO and Fe powders as starting materials. The surface morphology, microstructure and chemical composition of the samples were investigated by field emission scanning electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The results reveal that the samples crystallize with cubic structure and grow along the [1 1 1] direction. Results of magnetic measurement show the samples exhibit room temperature ferromagnetism without the formation of magnetic clusters. The saturation magnetization of the samples decreases with the increase of Fe concentration. From the first-principles calculations, it is strongly proposed that the magnetic state are depend on the distance between Fe dopant atoms. Combined the theoretical calculations with the experimental results, it is suggested that C vacancies play a vital role in determining the magnetic properties in Fe-doped SiC nanowires.

Aurivillius phase BaBi3.5Eu0.5Ti4O15 (BBET) ceramics were synthesized using a solid state reaction method. X-ray diffraction analysis confirmed that the compound is a four-layer Aurivillius oxide with tetragonal space group I4/mmm and Raman spectrum indicated that Eu3+ ions occupy the A site. It was observed that the average grain size is 0.5–2.5 μm by the scanning electron microscope. The photoluminescence spectra showed that the intense emission bands centered at about 593 and 615 nm are due to the transitions of 5D0→7F1 and 5D0→7F2 of Eu3+ ions respectively. The temperature of dielectric constant maximum, the room temperature dielectric constant and loss at 1 MHz are 373 °C, 222 and 0.013, respectively. The activation energy of dielectric relaxation was estimated to be 1.17 eV, which could be attributed to the thermal motion of oxygen vacancies. The BBET ceramics had a remnant polarization (2Pr) of 0.75 μC/cm2 at room temperature. The results suggest that BBET ceramics can be considered as a promising multifunctional optoelectronic material.

•Polycrystalline Bi4Ti3O12 film was deposited on FTO substrate by a sol–gel technique.•An obvious photovoltaic response for the Bi4Ti3O12 film was observed.•Time dependence of the zero bias photocurrent density indicates a repeatable photocurrent.•Schottky barriers are the mainly driving force for the separation of phto-generated carriers.Bi4Ti3O12 (BTO) film has been successfully fabricated on fluorine-doped tin oxide conductive glass substrate by the sol–gel technique. The optical band gap of 3.37 eV can be estimated from the UV–vis absorption spectrum. Piezoelectric force microscopy measurement confirms the local ferroelecitity of the BTO film. Seen from the J–V curve, the short circuit photocurrent density is about −75 nA/cm2 and the open circuit voltage is about 0.13 V under the incident light intensity of 100 mW/cm2. The time dependence of the zero bias photocurrent density with light ON/OFF demonstrates stable and repeatable instantaneous photocurrent. It is suggested that the interfacial Schottky barriers are responsible for the separation of electron−hole pairs in the BTO film.

Single crystalline Mn-doped 3C-SiC nanowires were synthesized by high-purity Si, SiO2, Mn and graphite powders. The scanning electron microscopy (SEM) results indicate that the diameter of the nanowires ranged from 30 to 200 nm, with a length up to tens of micrometers. The results of high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) indicate that Mn entered into SiC lattice and the nanowires grew along the [111] direction. Superconducting quantum interference device (SQUID) results show that the nanowires exhibited room temperature ferromagnetism (RTFM) behavior. The possible origin of the ferromagnetism has been fully discussed. The RTFM of the nanowires makes them potentially useful as build components for spintronic devices.Highlights► Mn has been doped into the 3C-SiC lattice. ► The growth direction of the nanowire is along [111]. ► The ZFC and FC curves coincide at around 300 K, meaning the presence of FM order. ► Clearly loops at 300 K indicate the robust FM ordering dominated the sample.